Contour Enthusiasts Group Archives Forums General Troubleshooting Head Gasket?

It seems like the question to be answered is where is the pressure coming from. Possible ideas are:
1) Air from the combustion chamber is crossing the head gasket into the cooling system.
2) There is a clog which is causing the water pump to create excess system pressure.

I thought of a few testing ideas:
You said the pressure builds up as soon as you start the car. Try removing the water pump drive belt when the engine is cold and running the car for just a minute and see if the pressure builds up. If you still get the pressure build up, the water pump is not causing it, so no clog. If there is no pressure build up, it's probably a clog.

Seems like a clog or restriction to me since you're not getting any heat. Let us know if you need more info.

Well it is OK not to have presure in the hoses when the cap is off. Two stupid questions: The cap itself, is it new and did you try and replacing it? Second: do you have bubbles in the coolant (the bottom hose ont he tank) when you revv it up? As I said, other than clogged system I dont see what elese can blow the hoses up, other than gasses comming in it. It takes a very small hole in the HG, small enough not to cause steam at the exaust and initially you may not see any mayo in your oil. I had the same problem, and it turned out it was a HG after all (prayed that it wasn't but it was). When the hole in the HG is so small it is difficult to trace it. I hope I am wrong, I wish you just have system clogged up. For what is worth you can try and flush or something to see it first. Fluids are tricky, if the flow trough the engine is not right it will overheat in a flash so check everyhting, twice!

I removed the belt for the water pump. I then started the car. The coolant level in the expansion tank went up only about a 1/2". The system had about 70% less pressure as compared to when the water pump is operating. Does this mean the system has a clog?

Thanks to all who have tried to help me!

it does not sound to good...did you notice any air bubbling in the expansion tank? You should have not had any rise in the expansion tank when you first started the car, and you should have had %100 less pressure...what do you mean by you had %70 less?? So your saying...you still had pressure?
If so....sounds like it could be a gasket leak, or cracked head. Before you go any further...why don't you take a shot at back flushing the cooling system with one of the hoses removed and the thermostat removed...see if you dislodge any debris. Or pressure test the rad system, with a pressure tester to confirm a head gasket leak.

I finally got the pressure tester. Well, I pumped the system up with 15psi. After five minutes it lost a 1/2psi. Next I performed a combustion leak test. As soon as I started the car it read 3psi. Five minutes later it was at 5psi. 15 minutes later it was at 16psi and close to overheating. I also had no heat while I performed the test. Next, I let the engine cool off and I removed the belt from the water pump. I performed the test again and it had the same results. What does this mean?

Sorry, been busy. I'm a little confused by your post above.

Now the first test you did was a pressure check of the cooling system right? You lost 0.5psi after 5 minutes at 15psi. I wouldn't call this much of a leak. Might even be considered normal. Could even be your test fixture leaking. This test says to me that your cooling system is sealing fairly good....move on.

2nd & 3rd test you call a combustion leak test. Are you monitoring crankcase pressure here? Or are you still hooked up to the cooling system and looking for leaks from combustion chamber to the cooling system?

Also, please tell us what location you are monitoring the pressure at. i.e. where did you hook up to?

The tester was still hooked up to the cooling system and I was looking for leaks from the combustion chamber into the cooling system? The tester was connected to the expansion tank?

Ok, so here are the facts as I understand them. Please correct any wrong statements.

1) The car did overheat about 6 months ago. You replaced the water pump & thermostat. Soon thereafter, replaced water pump again with NAPA unit when car almost overheated.

2) With the pressure tester hooked up to the cooling system and the water pump deactivated, you get an immediate 3psi pressure when you start the car.

This would seem to be a good indicator of a combustion leak. Especially since the air in the cooling system has not had time to heat up & expand. Sources of combustion leak that I can think of are:
A) Head gasket failure.
B) Crack in the head between combustion chamber and coolant passages.
C) Exhaust leak. i.e. a crack in the cylinder head in the exhaust port lets exhaust gases into the coolant passages.

3) With engine off, you apply 15 psi pressure to cooling system. You see 1/2 psi drop in 5 minutes. This may reinforce #1 above. However, there could be many sources for this leak besides a head gasket.

4) With water pump drive installed, the car will overheat just idling in about 15 min. I am assuming that your thermostat is still removed here. Are we sure that water is flowing through the hoses? Can you feel the hoses get warm? Does the radiator get hot? Do the fan(s) come on? If it's not flowing then:
A) There's an obstruction
B) Air is blocking it??
C) The pump is not really pumping even though the input shaft is turning. Loose impeller?

5) You consistantly cannot get heat from the heater even with the engine almost overheating. From what I have read, this commonly occurs when there is a bit of trapped air in the system. Perhaps caused by air from #1?

Other CEGers, more input would be appreciated. I'm at my wits end here. I'm much more familiar with the actual engine than any accessory equipment.

I had some free time so, I worked on the overheating problem today. I installed a clear tube in between the heater hoses. I started the car and turned the heater on.
What I noticed was nothing through the clear tube. It was have full with no flow. I turned the heater on and off still nothing changed. Something is clogged, right? Does any one know the complete flow path of the coolant in the cooling system? Is it possible for the water pump to spin in the wrong direction?
Thanks again, J.