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Old 09-16-2003, 06:55 PM
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Red face Cooling System (Way Too Much Pressure) ???

Hello,

Well, my engine likes to blow coolant out the overflow bag and all up under my hood. It really doesn't seem to matter if the engine is running hot or not. It appears to be when I step on it.

I have checked everything in the system (the thermostat works fine, the water pump works fine) and today I took it to a rad shop to have them run a pressure test on the system and to check for exhaust in the coolant (indicating a blown head gasket).

But everything checked out fine. No exhaust in the coolant and the rad cap is working fine.

The one thing the person did say is that my coolant flows like a river and that there are no baffles in the top of the radiator to slow down the coolant from flowing so fast. He seemed to think that the coolant is moving too quick and not getting a chance to cool down, thus making the coolant boil over and explode out the overflow bag. He said it's a possibility.

What do you guy's think? I'm kind of stumped now.

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Old 09-16-2003, 07:15 PM
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Quote:
The one thing the person did say is that my coolant flows like a river and that there are no baffles in the top of the radiator to slow down the coolant from flowing so fast. He seemed to think that the coolant is moving too quick and not getting a chance to cool down, thus making the coolant boil over and explode out the overflow bag.
No not true on the rad flowing to fast, anyway it comes out the bottom of the rad, its the thermostat's job to keep the coolant in the block to absorb the heat, the higher the degree thermostat the more heat is taken away, you want the coolant to stay in the motor as long as possible. The pressure cap can be bad and not releasing the pressure it sounds like.
I would try a new pressure cap.
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Old 09-16-2003, 09:11 PM
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??????????????????????????????????

The thermostat responds to engine temp, not radiator temp. If the cooling system is not able to cool the water fast enough to cool down the engine, you will either have a hot running engine, or it'll over heat completely and blow all the coolant.

The job of a thermostat is to keep an engine at a pre-determined temperature. When the engine is cold, the thermostat is closed, preventing the water from circulating. When the engine temp reaches the same temp as the thermostats rating, the thermostat opens to begin cooling the engine down.

Normally, the thermostat will open a small amount, allowing cooler water from the radiator to enter the hot engine and cool it down. Once the engine cools down some, the temperature sensitive spring will close the valve in the thermostat and wait for the engine temp to rise again to the temp that the car maker requires. Its normally and endless cycle of "engine heats up, thermostat opens, engine cools down, thermostat closes, engine heats up" and so on.

In an ideal world, the cooling system will be adequate enough to keep the engine from over heating.

Once the engine temp and the radiator water temperature exceeds the rated temp of the thermostat, the thermostat will stay completely open until the engine is finally allowed to cool down, or it will over heat. At this point, about all you can do is shut down the engine and wait for things to cool off.
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Old 09-16-2003, 10:10 PM
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It's not a temperature sensitive spring, it's the wax/metal shaving paste that responds to temerature. This 'goo' is inside the little piston that actuates the 'valve' by expanding with an increase in temperature.

Have you checked the radiator cap?

Did you do the cooling system pressure test with the engine at operating temps?

Did you perform the combustion gas test under a simulated load with the engine at operating temps as well?

Was this motor recently rebuilt (indicating heads might need retorqued)? This one would be a likely culprit due to the fact that you said "It appears to be when I step on it".

Has this car been severely overheated just prior to this problem?
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Old 09-16-2003, 11:04 PM
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Quote:
Originally posted by BstMech
It's not a temperature sensitive spring, it's the wax/metal shaving paste that responds to temerature. This 'goo' is inside the little piston that actuates the 'valve' by expanding with an increase in temperature.

I stand corrected on the technical operation of the thermostat valve.

Mark
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Old 09-17-2003, 08:59 AM
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Check the number on the cap for the pressure rating, should be 12=14, I would think the rad. shop checked all that stuff, but! How did they check for combustion gas? Has to be cap or head gasket?

I'd find a new radiator guy!
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Old 09-17-2003, 10:44 AM
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If it blows out the coolant with no reserve to catch it and allow it to be sucked back in for proper cooling , you can be cavitating with a air pocket this would make air bubbles.
Usually with a head gasket, the bubbles are more with speed and most of the time blow it out of the radiator with the cap off. Get a good reserve tank or try it with a 2 qt. plastic bottle with a hole in where the hose goes into it and about 1" from the bottom.
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Old 09-17-2003, 12:53 PM
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For what it's worth, my 455 in my 55 truck puked each time I stopped, nomatter how I drove it. The message from this forum said to increase the pressure on my cap from 7 to 13-14 lbs. I did and problem is solved!
I'd really try a new cap.
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Old 09-17-2003, 01:07 PM
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I am going with BstMech here. Sounds to me like head gasket. It sounds like you have enough seal to keep it in check untill you floor it and combustion pressures go up. What is the history of the engine?

Chris
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Old 09-17-2003, 02:15 PM
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Old 07-28-2006, 11:28 AM
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I had a similar problem. I had built a 350 rocket in a 72 cutlass fastback and had advanced the timing a little cause it seemed to run stronger. The downfall was the cylinder pressures raised when I would get on it, it would puke all over its self and push the coolant in the radiator into the overflow tank and all over the ground. I returned the timing to where it was supposed to and never had a problem again. I than just played with the advance curve in the distributor. Hope this helps!
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Old 07-28-2006, 12:20 PM
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Cheap first then gaskets

I think I'd try the cheap ways before I pulled a head - an new performance high flow 180 degree thermostat and a new performance 13-15 pound radiator cap. Get quality performance parts, not Auto-Zone or similar companies that sells foreign made junk.

If it still does the Old Faithful act, then go for a good compression test - including a leak down test which should tell you conditions in each cylinder - head gasket (and rings/valves). Some of the clone Chevy engines that Oldsmobile and Pontiac used did have some head cracking problems at the middle cylinders.
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Old 07-28-2006, 12:40 PM
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Going back and re-reading your original post....you said that it does this whether it is hot or not....... and does it more when you step on it....That tells me....Blown Head gasket.
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Old 07-28-2006, 06:23 PM
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Doc here,

It's really simple...

Pull the plugs .. If one is water soaked It most likely a blown head gasket..

Fill it full of water and crank it..if it pumps water out the plug holes..it is a gasket / head or block..

Do a Compression/ leak down If it is blowing water as bad as you described you should have a Cylinder (or more) that has no compression..

Is it blowing water (tons of it) out the tailpipe..? Does it misfire? Does it blow White steam out the pipe? lock slightly on starting? all symptoms of gasket / mechanical damage.

Doc
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Old 07-28-2006, 06:30 PM
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Well... it has been 3 years since he made his post What did the problem end up being?
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