# stoopid question lol



## redhotgto66 (Sep 11, 2021)

i've been putting in a new timing chain in my 400, along with that i've replaced everything new along the way, water pump, hoses, thermostat, etc etc.
my timing chain cover was rotten along with the plates so i got a better one also, so all should be good right?
well got it started last night and it ran fine, but after 4 min of running the temp shot up like a rocket ! litteraly the temp gauge went up like a second hand on a clock ! shut her down let cool off over nitgh, checked the water this morning, added more, start her up again and runs 4 min and temp rises like a shot again!
ok i have'nt done much mechanic work in years but my guess is the thermostat is'nt opening, sound right to you?
thanks for any ideas


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## PontiacJim (Dec 29, 2012)

redhotgto66 said:


> i've been putting in a new timing chain in my 400, along with that i've replaced everything new along the way, water pump, hoses, thermostat, etc etc.
> my timing chain cover was rotten along with the plates so i got a better one also, so all should be good right?
> well got it started last night and it ran fine, but after 4 min of running the temp shot up like a rocket ! litteraly the temp gauge went up like a second hand on a clock ! shut her down let cool off over nitgh, checked the water this morning, added more, start her up again and runs 4 min and temp rises like a shot again!
> ok i have'nt done much mechanic work in years but my guess is the thermostat is'nt opening, sound right to you?
> thanks for any ideas


If you did not mess with the distributor timing and you know that the timing marks lined up on your gears, then I would be looking at the T-stat.

Retarded timing can cause an engine to raise in temp. Did that one myself on a fresh rebuild (timed by ear) and could not figure out what was causing the engine temps to soar after starting - shut the engine down, let it cool, and started the break-in again with same results. The tell-tale was that my exhaust manifolds got visibly hot and the paint burned right off the heads at the exhaust ports. I called Comp Cams to see if it was a "cam" thing and thy said advance my timing. Sure enough, that did it. The engine ran/sounded fine and that was what threw me off.

So if timing is good, then I would assume T-stat since you did the plates. Open the radiator cap and watch for coolant to be flowing which should help you answer the question. Check your coolant level as you could have had an air pocket.


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## redhotgto66 (Sep 11, 2021)

well the timing should be fine, went top center as i should when installing the chain, checked the 1 cylinder and it was at the top of its stroke. it starts right up easily, runs fine, and the mark was dead on the line on harmonic balancer. 
i was kinda wondering about the hole below the thermo that goes from intake to timing cover housing, could it be clogged with sealent? just grasping here but will ck thermo later today.
thanks for help


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## PontiacJim (Dec 29, 2012)

redhotgto66 said:


> well the timing should be fine, went top center as i should when installing the chain, checked the 1 cylinder and it was at the top of its stroke. it starts right up easily, runs fine, and the mark was dead on the line on harmonic balancer.
> i was kinda wondering about the hole below the thermo that goes from intake to timing cover housing, could it be clogged with sealent? just grasping here but will ck thermo later today.
> thanks for help


OK, sounds like timing is not it.

The small hole is a bypass and should not be an issue even if plugged - which some do.

Your best friend here would be an inexpensive hand held laser temp gun. You can verify the laser temps against any gauge you may have and will quickly point you in the direction needed to locate the cause of the overheating.

You can just swap out a T-stat which would be fast enough and cheap if you think that would cure the overheating. T-stats, even new ones, can go south in short time.

Does your engine have the later 11-bolt water pump and did you replace the rubber sleeves? They fit into the timing cover holes and go up against the back of the metal plate.. See photo.

Did you clearance the stel plate/impeller gap?

Did you replace any belts? I have found that some of the auto store V-belts are not wide enough to catch on the inner shoulders of the pulley and will slip or sit low enough that they ride inside the pulley gripping nothing. Check belt tension and that the belts are riding up high on the pulleys and not sunk in deep. If slipping, and you won't hear belt squeal, it could cause the engine to overheat.


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## geeteeohguy (Feb 2, 2008)

What Jim said about the plates and the clearance. Are the plate(s) even in place? What year engine? 8 and 11 bolt timing covers use different set-ups. 
One thing to look at when you fire it up....does the upper rad hose get hard to squeeze in the first 4 minutes? If so, suspect blown head gasket/cracked head and combusiton gasses are getting into the cooling system. Time to check the radiator for hydrocarbons and the oil for coolant. Normally an engine will run 5 minutes or more with a closed T-stat and only get up to 'stat temperature. The fact it's going up like a second hand on a clock is concerning. The rad hose test will confirm this, also will tell you if your 'stat is stuck closed (hose will be soft and squeezable to touch as it won't be pressurized yet.)


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## Sdsmith66 (Nov 4, 2018)

You might have an air pocket, I have had trouble with that in the past. it will get hot real quick.


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## BLK69JUDGE (Jun 10, 2010)

Plates sounds plural 
As in pre 69


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## redhotgto66 (Sep 11, 2021)

ok just in from the shop, got a edelbrock thermostat today put it in problem went clear away !
i went down to a 160' thermo and it has never run this cool! to answer the belt question, yes replaced them, yes got them too skinny 3/8'' and yes they make too much noise ! it idled for over 30 min and never went above 180'
thanks for all your help guys


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## redhotgto66 (Sep 11, 2021)

pontiac jim, where do you suggest getting good belts ? and no i have the 8 bolt pump and what i pulled out was 1 plate behind pump, i had a pair of perfect plates so i put those in. they needed no seals, thanks again


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## geeteeohguy (Feb 2, 2008)

Still have no idea what year this is he's working on.


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## PontiacJim (Dec 29, 2012)

redhotgto66 said:


> pontiac jim, where do you suggest getting good belts ? and no i have the 8 bolt pump and what i pulled out was 1 plate behind pump, i had a pair of perfect plates so i put those in. they needed no seals, thanks again


I have had the best luck with the Dayco brand "cogged top" belts. They fit into the pulleys like they are supposed to and was the end to all my woes of throwing belts at high RPM's. I also run them on my '73 Fury without issue. Advance Auto seems to carry them, but you may have to ask for them and don't accept anything less - find another store locally or order online.


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## mcguiremcd (May 23, 2012)

PontiacJim said:


> I have had the best luck with the Dayco brand "cogged top" belts. They fit into the pulleys like they are supposed to and was the end to all my woes of throwing belts at high RPM's. I also run them on my '73 Fury without issue. Advance Auto seems to carry them, but you may have to ask for them and don't accept anything less - find another store locally or order online.
> 
> View attachment 159418


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## mcguiremcd (May 23, 2012)

Agree with Jim on belts. Every other belt I had on my car squealed.


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## armyadarkness (Dec 7, 2020)

I have found that most owners, somehow, retrofitted their cars with belts that were too narrow, over the course of the cars 50+ year life. Im not really sure how this occurred, but I see it a LOT!

When no amount of tightening stops the squeal, try increasing the belt width. It cured chronic, embarrassing squeal on my Vette and GTO.


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## redhotgto66 (Sep 11, 2021)

ok thx guys, i will try them a little thicker and look for the daycos, may have to order online somewhere


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## armyadarkness (Dec 7, 2020)

redhotgto66 said:


> ok thx guys, i will try them a little thicker and look for the daycos, may have to order online somewhere


NAPA has them


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## redhotgto66 (Sep 11, 2021)

ok i'll try and find a napa parts, dont have one here anymore


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