# Coolant in intake manifold beneath carburetor



## Ol Girl 1967 (Jan 10, 2021)

Hi guys. So, my first technical question and post. I've tried searching forums for answers first and couldn't find my situation. I hope this isn't re-hashing something that's already been discussed! And I apologize for the long read, but I want to give as much information as I can. 

When we picked up the 67 LeMans last May she ran decent enough. It has a 326 2bbl engine, 2 speed trans. There were some things to be desired though and I quickly got to work. I have the service manual for the car and have been reading the forum a TON. 

So I started with the engine bay clean up and look over. I found the carb completely filthy inside - mostly all black with a sooty like buildup. I found the choke heat tube internal to the intake manifold to be rotted away. That and poor air filter setup likely leading to the soot-like/dirt buildup inside carb air horn and throat. The choke housing looked the same. So, I decided to work on this situation. 

I picked up the choke heat tube for manifold from Ames. Also picked up a new Fel-Pro intake gasket set. I removed the carb and intake. Cleaned up everything real well and looked over parts. I didn't find anything that looked alarming or needing addressed besides what I was set out to do.

The choke tube install went well. Ends of tube flared out well making a good seal, with the tube left very solid in position. Next I installed the intake manifold. That also went very well. I read over the manual on the procedure thoroughly and read as much as I could on here for any tips and pointers that experience brings. Gaskets went on well. Only sealant used was at timing cover to manifold seal, gaskets left dry on both sides. Torqued the long front bolt first, then in a pattern found here tightened intake bolts incrementally until reaching 40 ft-lb. Everything seemed to be pretty text book - as described and expected. The car ran well after the work.

Not too long after the choke/intake job and a few hundred more miles, I started experiencing some smoke at startup. Grayish-whitish. It would last about 30 seconds or so and not happen again the rest of the day, regardless of stops and restarts. However, it continued to happen with the first start of the day with the amount of that initial start smoke becoming slightly greater, but still clearing up after about 45 seconds and not coming back rest of the day. The cloud was actually kind of embarrassing! 

Now that was how our driving season ended, figuring I'd pick up on fixing this when the weather warmed up. Over winter I read about what I could be experiencing and initially started to consider valve stem seals because of similar symptoms. However, I wasn't convinced as it didn't do this initially and it started after the intake job. Further reading and discussion has lead me to think I could have a coolant issue. I have not needed to add any coolant as it appears to be a good level in radiator. There is a slight wetness, not a puddle, on the front of the valley pan under the thermostat housing, though I don't believe it to be coming from there or the timing cover to intake seal/bolt. I removed the carburetor and found coolant in the intake manifold just below the carb opening in the lower plane of the intake. There was not any in the upper plane. It wasn't a lot, but enough to see the green sheen of coolant. I used a white piece of paper towel to confirm the color of what I was seeing. The color was green, not even dirty.

I have checked the oil and it looks like clean but used motor oil. Not the description of being contaminated with coolant. I checked coolant in the radiator and don't suspect oil contamination there, either.

So, I picked up another Fel-Pro intake manifold gasket set as I suspect that somehow the gasket(s) may be the culprit. But before tearing it apart again, I wanted to get your thoughts. My question to you is... is there something I'm missing here? How else could coolant be making it's way to just beneath the carb opening of the intake manifold? I can understand seepage making it to adjacent fuel port(s) of the cylinder head (via intake gasket seepage), but up to underneath the carb? In only one plane? There is no evidence of coolant in the carburetor. There is also no evidence of coolant in the PCV valve or tubing leading to lower plane, fortunately. (Side note: PCV tubing leading to upper plane was removed and the port closed before I bought it and have not been able to determine why, or ask PO about it, or even know if it's something needing corrected. That's another post.)

Thanks in advance for your time and thoughts on this. Looking forward to getting her back on the road!


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## Jared (Apr 19, 2013)

This sounds like unburned fuel upon initial start up. You could be slightly flooding it on initial start up or there could be something just off on your carb setup. There really isn't any way for coolant to make it to the carb.

The coolant on the valley pan is most likely coming from the rubber gasket at the front of the intake (the one to the water pump you mentioned). Mine leaked there when I first got it and then stopped. When I replaced the engine, I put a very thin coat of RTV on both sides of the gasket to keep it from seeping.


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## BLK69JUDGE (Jun 10, 2010)

bummer
here is my take,,, on the situation
if its green on your towel its antifreeze
this time use a little silly cone on the doughnut both sides between the intake and timing cover DONT snug it up tight just real close not too much to plug the hole either just a nice film
I think your intake is just a bit tilted and its drawing coolant into a runner
on the intake,,, its happened to me also...
pull the intake it should show where it didnt seal,,,,
thats where I would start ...
great information in your post....
also if you pull the plugs out you may see a real clean plug and thats a clue to that cylinder having the intervention of coolant into it and give you a clue of where the coolant is coming from
stinks to do it twice but ....most of us have been there before...
keep us updated ... super clean mating surface for the felpros are needed
I also on older motors like to fire up the engine with LOW coolant radiator cap loose
get the engine warm to the touch at the gasket area
turn the car off retorque ...let it cool for a couple hours ,,,retorque ....
the permatex sealer at the timing cover should have set up ...
top the radiator off go for a drive 


something else that thru me for a curve one time was ,,,, since the antifreeze is oily you NEVER want it on a gasket surface after you drain the coolant and then pull the intake you need to make sure the coolant
is not visable in the head ,,,, old towels bouncing the front suspension
paper towels ... get that coolant level LOWER in the head/block
so when you clean the gasket surface with BRAKE CLEAN and a clean towel there is no residue of antifreeze ..or chance of it splashing out of the coolant ports.... dont use anything too abrasive on intake and head surfaces...green scotchbrite by hand should scuff it up enuf....

Scott


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## geeteeohguy (Feb 2, 2008)

The only way you are going to get coolant INSIDE the intake under the carb is if you have a cracked head or leaking head gasket. Coolant cannot get there from the T-stat, and the front runner on the intake that goes to the timing cover does NOT connect to the intake ports on the head, just the cooling passages. Time for a block tester and a leak down test. I'm betting cracked water passage in one head. When warm, the head expands and seals up the crack. Betting a treatment with KW Head and Block seal would likely fix the issue permanently.


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## BLK69JUDGE (Jun 10, 2010)

wouldnt you think if it was the head that it would go straight into the combustion chamber ?? not backwards up the intake runner against
the direction of airflow ??


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## geeteeohguy (Feb 2, 2008)

Yeah, but how else could coolant get into the intake under the carb? I agree it's very strange. I'd like to do a pressurized cooling system check with the carb off and take a look see.


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## Lemans guy (Oct 14, 2014)

I just found a coolant leak with my smoke machine. Coolant was dripping off back of the block. Put in some dye looked around. And saw a bunch on the valley pan. Suspected an intake runner. But it was leaking at the thermostat housing.

To really see it drained just the radiator at the peacock. Then smoked it through the radiator cap. Sowed right up. Any good shop will have a smoke machine. Or maybe you can find one, drain the radiator. Smoke it, you will find the leak.

Cracked head like GeeTeeOhh guy said most likely. But there are other ways. If you have any rubber vac hose laying in a low spot that develops a slight leak, or at it’s edge, and coolant from a leak is lying in a low spot like the valley pan, near it, the vac hose could suck it in.

so make sure you don’t have any vac hose near any low lying coolant………leaks can run down hoses and be unrelated to hose….Agree if head has slight crack that KW head seal is good stuff and worth a try while leak is small.


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## geeteeohguy (Feb 2, 2008)

Lemans Guy, excellent point on the vacuum hose possibility. A million to one shot, but a shot. And a smoke machine is totally the way to go to find leaks. No better way, actually. As for the KW, I have seen that stuff perform miracles for the past 40 years. Most snake oil fixes are a waste of money, but all the KW stuff delivers!! 👍


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## Ol Girl 1967 (Jan 10, 2021)

Guys, thank you very much for the information you've shared. This certainly has me stumped, but I know I don't have the knowledge and experience that you all have.

Jared: I didn't rule out unburned fuel or flooding, but color of the smoke wasn't convincing me. There was also no smell that lead me to that thought. However, the carb has performed satisfactory, but probably is due for a serious cleaning and/or rebuild. And I believe the valley pan spot can only be from the timing cover to manifold connection, Stat, or possibly gasket seepage from coolant crossover. I haven't been able to pinpoint that yet.

BLK69Judge: The manifold install has been 1st on my list of suspicions as the problem didn't start until after I did the initial work. Though I felt I did a pretty good job of removal, prep, repair and install, it was my first intake job. And the the paper towel test certainly showed green fluid when swabbed into intake beneath carb. Not dirty green, not (motor) oily green... just green. I have not yet pulled plugs to inspect and see if they have anything to tell me, but I will. I didn't mention in my first post, but I did check torque of the manifold bolts. As much as I hoped for a smoking gun there, all were still good incrementally up to 40 ft-lb. 

Geeteeohguy: I agree that a coolant getting to that location isn't going to be from leak external to engine, like Stat. The coolant passage was a consideration of mine only if perhaps seepage through the gasket lead to a fuel runner. I could understand that seepage making it to combustion chamber and burning off at startup, but not against gravity up in to the manifold. It certainly stumps me how it could get to under the carb from any place. Head, block or gasket are what I was hoping not to hear, but must be considered. You mentioned KW Head and Block Seal. I looked at their website and see several products available with different methods of using them. Any one you recommend specifically? As for testing, I have a leak down tester and plan to do that. As well ad compression test (may as well) and when I get my hands on a coolant system pressure tester, that too. When you mention block test, may I ask what I should be doing to perform that? I'm not yet familiar with block test.

LemansGuy: vacuum hose has also come to mind for me. Specifically, the PCV to manifold passage. The PCV valve is pretty close to the heater hose nipple on the right head and certainly any seepage from the nipple to the valve would be sucked by vacuum to dang near where I found the coolant to start with. However, I didn't see any evidence of a coolant leak at the nipple or trace of it at the PCV valve or PCV hose connections. And the smoke is only occurring at first start of the day and only briefly. If the engine cooling down after being turned off is allowing the coolant to move where it shouldn't, vacuum wouldn't be available anymore when shut off and couldn't be sucked from the nipple/PCV area. 

Or, maybe it could? If the suction of steam in to the manifold were taking place, but not enough to be evident in exhaust during warm operation, after the engine cools the steam would condense back to fluid, building up and collecting where I found it, then being burned up at startup. Hmm... is that possible?

As frustrating as it could be, so much fun!


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## geeteeohguy (Feb 2, 2008)

The type of KW block and head sealer to use is the glass-based stuff. You drain the system, fill it with water, drain it, fill it with KW and water, run it for awhile, and then drain the system and let it set up overnight with the rad cap off. Then fill with coolant and water the next day and you're off.


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## toomanytoys (Dec 8, 2020)

Don't forget that the intake manifold is under vacuum, so it can easily draw-in coolant from a gasket leak. Good luck. I have had a few go-arounds with intake gaskets too. I hope it isn't a cracked head.


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## Lemans guy (Oct 14, 2014)

It is weird, make sure you consider whether coolant which can run down the valley pan and drip off of the rear of the block and trans is not the culprit. You may two separate events. Coolant leaking at a coolant runner or even thermostat housing or heater hose, and then running somewhere, like down the vacumn hose for the trans modulator valve…if you have one. Those modulator valves have a cup like structure at the point where the hose attaches and of course it is hooked to manifold vacumn, so it could then get sucked in the intake.

Unlikely but possible. I am with GeeTeeOhh guy probably a slight crack in head causing it.

one other thing coolant expands throughout the system-upon shutoff. This is when your overflow tank will fill or coolant will drip from your overflow hose. It expands both in the engine radiator and throughout the system. When it does it may somehow locate some coolant to a place where a hose or bad intake gasket could suck it in on start up. White smoke for a minute, then it is gone, because it only happens when it is expanding. Then you drive all ok. Then repeat.

Here is agood way to find a coolant leak. Put some coolant dye in for extra help. All auto parts stores have little bottles of it. When cold put you coolant testing pump on the radiator opening pump it to 16 lbs and start the car, let it idle until at hot operating temperature. Leave the-pump on the radiator overnight. You will see the leak in the morning. Make sure your garage or driveway is clean before you start. You can even put some cardboard or paper down overnight. The dye helps if you then are backtracking the leak. Good luck and let us know how you do.


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## Jd70 (Jul 4, 2019)

Does your car have A/C ?? In the big picture you posted
where does the line red arrow pointing at go to?? 







First try at inserting pic hope it works. In case it didn’t work the line that is pointing straight to the back of the carb area.
jd70


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## Ol Girl 1967 (Jan 10, 2021)

Hi again. It's been a long few days with barely enough time to read and reply, let alone turn some tools! But I have been reading your posts and thank you again for the great ideas and suggestions. I now have several days to get in it, so I'll post updates as I find more. Still need to get the coolant pressure tester. Been looking at FB Marketplace, hope to have one today.

I'm thinking intake gasket replacement will probably happen. I installed these dry last time and would really prefer to do that again. If dressing the gaskets is necessary, what are guys using to do it and where on gasket? Just around coolant passages? Around runner, too? I know about the round seal at front for sure.

Jd70: your pic edit turned out good. That line you ask about is the vacuum line to transmission. The other is for brake booster. A third is for distributor. All 3 connect to one fitting at rear of throttle plate at bottom of carb. No other vacuum connections beside PCV valve at rear valley pan to intake.


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## geeteeohguy (Feb 2, 2008)

Intake gasket is a waste of time and money if you end up with a cracked head. Do a pressure test or smoke test FIRST. A bad/leaking intake on a Pontiac won't cause your coolant in the manifold under the carb problem--- the water can't get there from the head and runner passages. On intake gaskets on Pontiacs, I use nothing but the gasket. The big deal is the sequence....the front thin bolt with the O ring (and sealer on it), anti-seize on the bolt, drawn up snug, BEFORE tightening the other intake bolts in a cross pattern. 
But fix the coolant leak first. The likelihood of a vacuum line with a crack picking up stray coolant from a T stat leak is about as likely as a pinhole leak in the radiator shooting a micro thin stream of coolant into the air cleaner causing your issue.....possible, but not likely. Check the cooling system for leaks....my bet is a cracked head.


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## Ol Girl 1967 (Jan 10, 2021)

Agreed. The intake gasket will be the very last thing to happen, and only if testing proves well. As for how the water is getting there, that's why I'm talking with you all. I don't fully know all the ins and outs of the head/block passages and how that can contribute. I also agree about the super low possibility of it getting in by means of vacuum lines or directly through carb. I'm guess I'm being optimistic that the cause isn't severe! And I am also trying to get any info and ideas together for what to be looking for when I start testing.

I really do appreciate everything you all offer! I will keep you updated.


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## Jd70 (Jul 4, 2019)

Ok automatic car.
1. Pull plugs, look for extremely clean or even a greenish tinted center of plug indicates burning of leaking coolant.
2. Burning or leaking anti freeze has a sweet kinda odor to it. Did the fluid out of manifold have this.? Nowadays new ethanol old gas can turn greenish but smell real strong of fuel. Smell test.
3. If sweet smelling a cooling system pressure test in order.
4. Smells of strong gas its carb related.

Reading your clues the car ran okay for a couple hundred miles before problems. Kinda rules out gasket job to me, not completely but kinda back burner.
The weird stuff is only one plane affected, same plane as PCV!! Now this is a looong shot, but could the weepage from thermostat be dripping, gathering on a porous, rusty valley pan area or gasket?? Maybe PCV sucking it in?? Dunno between looking at plugs from that plane and other diagnosis might get you closer to problem.

JD70


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## Ol Girl 1967 (Jan 10, 2021)

Ok, it's been a while... my apologies. So, I had the opportunity to spend a little time with her and I'll share what I found so far. I am posting pictures and some short videos.

I added coolant dye and used a UV light to help. I did a coolant pressure test and pressure diminished a bit over just 2 hours. It wasn't all the pressure, but noticeable. I only kept it under pressure 2 hours, so I am unsure what a longer period will look like. I did find a leak at the thermostat hose connection but found no other visible leaks. It appears that is where the coolant at the valley pan is coming from. When I fix that leak, I will do another test to see if that is where pressure is lost. On a side note, I know the thermostat housing is on incorrectly. It was positioned that way when we bought it. Last summer when I did the intake job, I initially positioned it correctly, but the hose didn't seem to fit well, so I put it back as I originally found it. Also, it should be noted that this hose connection leak didn't happen when I ran the engine today, only under pressure test. This is the first 3 pictures.

Under suggestion, I pulled the plugs to see what they tell me. A couple plugs looked a little fouled, but not a lot. Half looked normal? A couple... eh? None of them smelled sweet or too strongly of fuel. I'm attaching pics for you to see. They are labeled with which cylinder, upper/lower manifold placement and gap. Gaps measured in the 0.036 neighborhood. I did put in new plugs and gapped them at 0.045, as the distributer is H.E.I. upgraded by PO.

While inspecting with UV light, I took a look in the carb. Found some spots that lit up in the air horn. I could see this green in both intake planes now after running. Pictures included, but not great. I pulled valve cover caps and found some areas that lit up. I couldn't get a good picture through hole. Same result on engine oil dipstick. I was concerned at first, but none of these "glows" were nearly the same as what I found coming from the thermostat. I used the UV light to look at new oil still in the container and found that it has glow closer to what I found in VCs and dipstick. I did the same thing with gasoline in a gas can in my garage and a new can of Seafoam with the same result. (I added a can of Seafoam to a fuel tank of fuel at the end of the season last year.) I can't be certain what was in the VCs, carb and dipstick isn't just what glows naturally under UV light. It makes me wonder if what I originally found in the intake is in fact coolant, or possibly an older mix of gasoline treated with Seafoam. An early post by Jared suggested possibility of unburned fuel or flooding at start up. The carb certainly needs gone through and the choke can act up on occasion. I ran the vehicle yesterday and today. Neither time did it smoke at start up like it did at end of last year. Today there was a bit, but not much. More from left than right and totally gone after running. I included pics of exhaust at start, smoke is hard to see in pic. I am including short videos of exhaust at startup, exhaust after running 10 miles or so, and engine after that same run. I have to put the videos on another post to avoid too many attachments in this post.

As always, I appreciate the insight and help!


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## Ol Girl 1967 (Jan 10, 2021)

This should link to Dropbox with the videos.









LeMans


Shared with Dropbox




www.dropbox.com


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## geeteeohguy (Feb 2, 2008)

Since there is 'stuff' in the slothead of the screw down in the carb, it had to come from the venturis, not up through the intake. I think you shot yourself in the foot with the seafoam additive. What to do: Install T-stat correctly. Fix any and all hose leaks. Apply pressure (13-16 pounds) and it should hold pressure overnight. If it does, you are good to go. Your plugs look lean if anything but hard to tell with unleaded fuels. Personally, as a retired tune up guy with 42 years tuning cars under my belt, I would throw away the aftermarket ignition and run the plugs at their intended .035 gap. There is zero 'upgrade' in running a big gap with HEI in the real world. Only in magazine articles and adds that sell the stuff.


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## PontiacJim (Dec 29, 2012)

Ol Girl 1967 said:


> Ok, it's been a while... my apologies. So, I had the opportunity to spend a little time with her and I'll share what I found so far. I am posting pictures and some short videos.
> 
> I added coolant dye and used a UV light to help. I did a coolant pressure test and pressure diminished a bit over just 2 hours. It wasn't all the pressure, but noticeable. I only kept it under pressure 2 hours, so I am unsure what a longer period will look like. I did find a leak at the thermostat hose connection but found no other visible leaks. It appears that is where the coolant at the valley pan is coming from. When I fix that leak, I will do another test to see if that is where pressure is lost. On a side note, I know the thermostat housing is on incorrectly. It was positioned that way when we bought it. Last summer when I did the intake job, I initially positioned it correctly, but the hose didn't seem to fit well, so I put it back as I originally found it. Also, it should be noted that this hose connection leak didn't happen when I ran the engine today, only under pressure test. This is the first 3 pictures.
> 
> ...


I am no expert on plug reading, but those don't look healthy. Read this article and check out how to read plugs. Look at the discoloration on your electrode ground strap and then look at the pics.






Reading spark plugs







www.crankshaftcoalition.com


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## Ol Girl 1967 (Jan 10, 2021)

Geeteeohguy, thank you for looking at the pics and insight. I added the Seafoam to a full tank of gas mainly to help the gas keep over winter. I did run it a couple times since doing it. Noticing the color even higher in the carb further lead me away from thinking coolant. I don't have the engine expertise but I just can't see how it could be coolant now. The color is totally misleading me! As for ignition, the original didn't come with the car, just what is there. I tried finding a make/model, but there is nothing there. Closest I could tell is maybe a Duralast brand. The 0.045 gap for H.E.I. I picked up through threads on the forum. So I decided to try it out. Do you suggest I convert back to points ignition? Or another ignition altogether? 

Pontiac Jim, thanks for the tip on plugs! That article is very informative. I had no idea there is that much to see in a spark plug. Comparing what came out to the article, I can't say any of them look satisfactory, now. I'll have to take another closer look.


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## BLK69JUDGE (Jun 10, 2010)

my small block 406 chev likes .038 gap on the hei
number 5 looks iffy


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## Mine'sa66 (Oct 30, 2019)

geeteeohguy said:


> Since there is 'stuff' in the slothead of the screw down in the carb, it had to come from the venturis, not up through the intake. I think you shot yourself in the foot with the seafoam additive. What to do: Install T-stat correctly. Fix any and all hose leaks. Apply pressure (13-16 pounds) and it should hold pressure overnight. If it does, you are good to go. Your plugs look lean if anything but hard to tell with unleaded fuels. Personally, as a retired tune up guy with 42 years tuning cars under my belt, I would throw away the aftermarket ignition and run the plugs at their intended .035 gap. There is zero 'upgrade' in running a big gap with HEI in the real world. Only in magazine articles and adds that sell the stuff.


As a current tuneup guy with 39 years under my belt, I agree.


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