# Radiator BLEW UP on way to shop



## jetstang (Nov 5, 2008)

Well, was taking my 70 Lemans to the body shop for paint today, 25 miles. Started running warm, 220 degrees on the highway. But, I have a ground issue, and the oil pressure gauge stays at 80 psi all the time, so don't trust them. In the middle of no where I stop, get out and check the engine, lower hose and radiator is warm, not hot, but is dripping a little water of the lower water neck. Drive on, gauge is pegged, trying to limp it in. Stop at light, guy tells me car is dripping, yeah I know. Turn into the gas station and BOOM, radiator blows, water on the windshield. Get it shutdown, no problem, got a flat bed and towed it to the shop. It cracked the seam on the rad about 4 inches.

I thought my failsafe thermostat was stuck closed, but now looked at it and blew through it, it's open, may not have been. Used the intake on my old motor as is, no issues ever.
I put the divider plate, tubes and seals in housing behind pump, didn't want any issues with cooling. While driving, I ran the heater to try to cool it and it blew hot air, so water was getting to the heater core, but not flowing to the radiator. I am getting a new thermostat and cap.
I don't know why it built so much pressure and blew out. I have to assume the thermostat was stuck shut, but it fails open. Any help is appreciated, I'm confused.
Sending unit for gauge is next to the thermostat housing.:willy:
Motor starts and runs fine, may have took a head, will have to wait and see.


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## grabber (Sep 23, 2009)

I dont know how old your radiator was but it sounds like your fins were clogged. I had that happen to me about 25 years ago in a Mercury I had and thats what it was.


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## jetstang (Nov 5, 2008)

grabber said:


> I dont know how old your radiator was but it sounds like your fins were clogged. I had that happen to me about 25 years ago in a Mercury I had and thats what it was.


I just restored the radiator last week, painted it all up. Radiator was cool to the touch.


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## Silver69GTO (May 25, 2009)

Yep. Been there.
Mine blew a tube in one of the cores.
I had a local shop re-core it because they said the tanks were fine.


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## geeteeohguy (Feb 2, 2008)

If the rad was cool but the hose was warm, there is a restriction somewhere. I have seen radiators blow from being run with a leaking head gasket/cracked head. Cylinder pressure goes thru the crack/bad gasket, enters and pressurizes the cooling system until the weak link blows. Hope it was just a stuck 'stat. One way to check for combustion chamber gasses going into the cooling system is to fire it up cold, and see if the upper and/or lower hoses get hard right away, before the engine is actually warmed up. If the hoses get hard in a minute or two, it's bad news. Good luck.


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## jetstang (Nov 5, 2008)

Good info GEETEEOHH. But why didn't the rad cap release the pressure? Can't check the cap, it's in the garbage. It seems like it had an air pocket under the stat, not letting it open, overheating the engine, but rad was still cool to the touch right after it blew. No obstruction I think. It ran hot since I built it. Just got it running right Friday night.


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## geeteeohguy (Feb 2, 2008)

It's sounding like a stuck 'stat to me. I had one stick on a fresh rebuild. Caught it in time, but it happens. An old trick on the install is to jam the 'stat open with an aspirin so you can fill up the system easier. Aspirin dissolves harmlessly, and no air pockets. Even with a good rad cap, it is unable to release enough pressure fast enough to overcome the combustion pressure in the system and it'll blow something: rad, hose, etc. Not real common, but I've run into it.


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## jetstang (Nov 5, 2008)

GTOguy, that's pretty much what I was thinking, odd though. That's the last fail safe stat I use. I like the aspiring idea, and if the car gets a headache... I just drill 1/8" hole in the stat to let it bleed off air and fill up. But, I couldn't with the stat I was using, next one will be a normal one. Appreciate the info. Rad wasn't done today, maybe tomorrow, will be good to know if I hurt it or not, don't think I did, but heads gaskets are quick and easy...


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## 66tempestGT (Nov 28, 2009)

jetstang said:


> GTOguy, that's pretty much what I was thinking, odd though. That's the last fail safe stat I use. I like the aspiring idea, and if the car gets a headache... I just drill 1/8" hole in the stat to let it bleed off air and fill up. But, I couldn't with the stat I was using, next one will be a normal one. Appreciate the info. Rad wasn't done today, maybe tomorrow, will be good to know if I hurt it or not, don't think I did, but heads gaskets are quick and easy...


thats the first time ive ever heard pulling the heads described as quick and easy. but i like your attitude. :cheers


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## geeteeohguy (Feb 2, 2008)

I like his attitude, too. It's the kind of attitude that gets cars built. I wonder how TMP's "quick and easy" '67 re-fresh is coming?


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## johnnylightning03 (Nov 27, 2007)

geeteeohguy said:


> If the rad was cool but the hose was warm, there is a restriction somewhere. I have seen radiators blow from being run with a leaking head gasket/cracked head. Cylinder pressure goes thru the crack/bad gasket, enters and pressurizes the cooling system until the weak link blows. Hope it was just a stuck 'stat. One way to check for combustion chamber gasses going into the cooling system is to fire it up cold, and see if the upper and/or lower hoses get hard right away, before the engine is actually warmed up. If the hoses get hard in a minute or two, it's bad news. Good luck.


:agree and if available someplace, you could also use an emission analyzer to sniff around the rad neck and see if if you can pick up any hc or co gas when it's running, just dont suck in any coolant and ruin the machine. also they make a combustion leak tester that uses a blue liquid that will turn yellow if co is present. it fits on the rad neck. i use this all the time on suspicious vehicles in the shop. we call it the pregnancy test. if it turns yellow your goin in. :lol:


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## jetstang (Nov 5, 2008)

66tempestGT said:


> thats the first time ive ever heard pulling the heads described as quick and easy. but i like your attitude. :cheers


Thanks, was a joke, but I'd rather pull a head on a pontiac then mess with the timing cover and water pump, that's a pain. Also, with new headers, all bolts come out and nothing will break, so way easier than the first time. If it's blown, what is my choice but to do the work??



geeteeohguy said:


> I like his attitude, too. It's the kind of attitude that gets cars built. I wonder how TMP's "quick and easy" '67 re-fresh is coming?


Thanks, TMPs project is crazy, mine is just a mild rebuild with issues.:rofl:



johnnylightning03 said:


> :also they make a combustion leak tester that uses a blue liquid that will turn yellow if co is present. it fits on the rad neck. i use this all the time on suspicious vehicles in the shop. we call it the pregnancy test. if it turns yellow your goin in. :lol:


Good info, will have to try that. Where do you get it.

Car seams to run alright, story to follow.


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## jetstang (Nov 5, 2008)

Got the rad back, rotted out and soldered up, but couldn't pick it up before closing. Told the body shop, he ran up and picked it up for me and payed! I payed him back, put the rad back in, he wanted to paint it first, I said I want to see it run right. We put the rad in, filled it up with the waterneck and thermostat out to make sure block was full. Full, bolted the thermostat and housing back on, drilled 2ea 1/8" holes in stat, put hose on, topped it off. Started car, ran great, 180 degrees, then 170 when 160 stat opened, no issues. Then, car stumbles and dies. No gas in filter, hmm, put $30 of gas and drove 20 miles. Well, put the gas in, looked down and crossover tube line is spraying gas onto the crossmember. Put clamp back on added gas, car runs alright. Then noticed electric choke I just put on isn't opening all the way, keeping the choke on some, bent the linkage to full open, car runs great! Adjusted the valves, pulled the valve cover with the car running, had a nice lifter tick. I guess Pontiacs have a restrictor to the valve train as they don't spurt oil like a Chevy does, no more tick. All is good, and I'm happy.arty:


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## Rukee (Feb 8, 2007)

sweet! :cheers


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