Cooling system overpressurizing?

[93nitemare]

Hello everyone. I have a 1993 Mustang with a 347 stroker motor, TFS high port heads, and Mr. Gasket 5807 Ultra-Seal head gaskets. A while back I over heated the car and it got up to 240 degrees. I pulled the heads off and got them checked for warpage and pressure checked. They are aluminum heads and were only warped .003 so the cylinder head shop took off .005 so they were true. They pressure checked good also.....so they said.

I got them back and used the Mr. Gasket Ultra-Seal HG's and torqued them all down to spec as per the service manual. One thing I didn't do is run a tap through the head bolt holes in the block.

After I got it together I took it for a spin and after about 4 miles of driving the temp crept up to 210 so I immediately shut her off and got it towed home.

Last week I rented the Cooling System Pressure checker from Autozone. I pumped up the cooling system to 16psi and let it sit for 24 hours. When I checked the gauge the cooling system didn't loose any pressure.

I then came up with this idea (to see if the HG is acting like a one way check valve) to pull one spark plug out each day and with 0 pressure in the cooling system and the pressure gauge hooked up to the radiator, start the car and time with a stop watch how long it takes to reach 10psi.

I did this the same time every day and let the motor cool for 24 hours before I proceeded to the next plug. Anyway here are the results:

Cyl# 1 - 2:35

Cyl# 2 - 3:20

Cyl# 3 - 3:07

Cyl# 4 - 2:55

Cyl# 5 - 3:15

Cyl# 6 - 5:44 Tested one more time for accuracy 5:35

Cyl# 7 - 3:16

Cyl# 8 - 3:08

As you can see 7 cylinders are close to 3:00 minutes while cyl# 6 is 2:40 away from the 3:00 average.

I'm guessing #6 is where my problem might be due to the fact when that spark plug is out all the compression is being expelled out threw the spark plug whole and not able to push past the HG into the cooling system. That's why it takes that much longer for the cooling system to build up pressure to 10psi.

Am I right in my thinking that the problem lies within/around cyl #6? That way when I pull it apart I can zoom in on that area.

If the head was cracked the coolant would leak back into the #6 cylinder with the motor off, right? Which didn't happen when I pressurized the cooling system for 2 days. I'm taking a stab at it thinking the head gasket is acting as a one way check valve b/c the void is so minute that 16psi won't push threw one way but 180+ psi will push threw the opposite way, right?

Thanks,
Nick

[MagicRat]

Welcome to AF.

Thats an innovative test procedure you have developed there. Congradulations for doing such a well-thought out and consistent diagnosis test before starting this thread.


IMO it is VERY peculiar that ALL cylinders are leaking air into the water jacket... and at such a consistent rate. IMO this is far too much of a coincidence to say that BOTH new gaskets are leaking in exactly the same way around all 8 cylinders.

IMO the heads are defective. For some reason, their manufacturing process is producing porous castings. TrickFlow's website says nothing about the heads being made in their own factories (or even American-made). Lots of aftermarket heads (or at least bare castings) are now made in China. This does not necessarily make them bad, but it means that TrickFlow has very little control over manufacturing quality. If problems occur in the Chinese plant, it may take a long time before TrickFlow engineers detect the problem.

Porous castings have happened before. International trucks had lots of trouble with porous castings in their older 6.9 diesel V8 motors.

It might also be a crack, but I think its unlikely that all 8 combustion chambers are cracked in the same way.

[curtis73]

I doubt it is leaking at all. If your pressure test turned up no leaks, then there shouldn't be any leaks. What I'm assuming is that more likely is that the running of the engine is heating up the coolant and causing normal pressure in the system. 2-3 minutes is a bit quick to reach 10 psi, but if that is the case your time deviations are nothing to worry about. Different atmospheric conditions from day to day will cause the engine to heat up in different ways, not to mention individual cylinder mixtures and heats are different.

Your test method (while brilliant and innovative) might not be an accurate diagnosis tool in this case.

Any other typical signs that might indicate a head gasket leak? Oil in the coolant, coolant in the oil, bubbles in the radiator, fuel smell in the coolant, uneven compression or leakdown results?

You may have already done all of this, but rule out the simple stuff first; air pocket in the jacket, stuck thermostat, abnormally advanced timing or lean mixtures, bad water pump, etc. One of the things you can do with that pressure tester is positively fill the block with coolant. Fill the radiator, open the highest point in the coolant system (upper rad hose, water neck, TB passage, heater core) and pump until you get coolant out. Most engines will self-purge, but some just refuse.

[93nitemare]

Originally Posted by MagicRat

Welcome to AF.

Thats an innovative test procedure you have developed there. Congradulations for doing such a well-thought out and consistent diagnosis test before starting this thread.

Thanks for the warm welcome.


IMO it is VERY peculiar that ALL cylinders are leaking air into the water jacket... and at such a consistent rate. IMO this is far too much of a coincidence to say that BOTH new gaskets are leaking in exactly the same way around all 8 cylinders.

If you go back and read my post again 7 of the cylinders build up cooling system pressure about equal. Then when #6 cyl is taken out of the equation it takes almost 3 more minutes to build up to 10psi. Which sounds about right....6 minutes versus 3 minutes. Because with the engine bone cold heat is what causes the cooling system to build pressure. So if you think about it with #6 out of the picture the cooling system is building pressure at it's normal rate. With #6 plug in I think it's building pressure too fast.

IMO the heads are defective. For some reason, their manufacturing process is producing porous castings. TrickFlow's website says nothing about the heads being made in their own factories (or even American-made). Lots of aftermarket heads (or at least bare castings) are now made in China. This does not necessarily make them bad, but it means that TrickFlow has very little control over manufacturing quality. If problems occur in the Chinese plant, it may take a long time before TrickFlow engineers detect the problem.

I doubt the heads are poured defective b/c these heads have gone LOW 8's in the 1/4 mile on turbo stangs. When i'm talking turbo I'm talking T88's and bigger with 25+psi.

Porous castings have happened before. International trucks had lots of trouble with porous castings in their older 6.9 diesel V8 motors.

It might also be a crack, but I think its unlikely that all 8 combustion chambers are cracked in the same way.

Again seven cylinders build up the cooling system pressure roughly equally until the #6 spark plug is out. I am doing my test with ONLY one plug out at a time and starting and ideling the car.

[MagicRat]

Originally Posted by 93nitemare

and starting and ideling the car.

Uh oh........ I missed this vital point the first time around. Sorry. I agree with your theory that compression gases may be leaking in a way that is not detected by the first cooling system pressure test.

However, the fact that the engine is running makes this test pretty worthless.

For any test, you need to eliminate all other factors and variables, such as the system being pressurized by engine heat.

Try the test again with the engine switched off. If the heads and gaskets are good, there should be zero pressurizing of the cooling system for all cylinders. If yes, your problem lies elsewhere

[534BC]

Try using an combustion gas tester if you want to test for gas in the coling system. They aren't very popular, but are very good. I see no inication of any syptom other than the car overheating , unless I am missing something.

Upon reading the op where it says "awhile back it overheated" brings up the question: was this a running vehicle that didn't overheat? or are we dealing with a brand new set-up?

[93nitemare]

Originally Posted by 534BC

Try using an combustion gas tester if you want to test for gas in the coling system. They aren't very popular, but are very good. I see no inication of any syptom other than the car overheating , unless I am missing something.

Upon reading the op where it says "awhile back it overheated" brings up the question: was this a running vehicle that didn't overheat? or are we dealing with a brand new set-up?

it was a running vehicle with a fresh 347 stroker motor with about 1000-1200 miles on it. then one day it overheated to about 240 degrees. i pulled the heads and took them to a cylinder head shop to get them pressure checked and checked for warpage. the pressure test was good and they were only warped .003 so they shaved off .005.

i got a new set of head gaskets, torqued all the bolts in sequence and to spec as per the sevice manual. drove the car 4 miles and it started to creep up again to about 215 before i shut it down. towed it home and started looking into it and analyzing the situation.

it has a new thermostat. when i start the car in my garage within a minute or two the upper radiator hose gets hard....which should not happen that quick. i tested this on my other mustang i just recently got rid off. i started it and ran it for a few minutes and the upper rad hose was still easy to squeeze and the temp gauge had not even budged.

does napa, advance, autozone, etc. have a combustion gas tester?

[curtis73]

Although rising temps are trouble, 215 and 240 are not horrifically dangerous temps as long as things aren't boiling. As long as its not boiling over, don't worry. Those heads are soaking up 2000-degree combustion heat. The difference between 190 degrees and 240 isn't likely to hurt anything. I don't even shut off until about 230.

Its possible that in the first 1000 or so miles you just didn't encounter any conditions that made it overheat. I know you already know this, but new thermostat doesn't mean good thermostat. Try a different one - even a used one, or take this one out and test it with a thermometer in a pan of water on the stove. How well do you trust the water pump? I suggest you invest in one of those little laser thermometers. They aren't expensive, but it beats burning your hands. Test temps in certain flow areas, like test both heater hoses, upper and lower rad hoses, left and right on the radiator. If you have more than about a 20-30 degree difference in any of those areas, there is a flow restriction; either from a bad pump or a clogged radiator or heater core.

I only mention this because (although you are very methodical and intelligent) sometimes we (myself included) start diagnosing from the top down. Assume its a head gasket because that's what you fear, and we end up missing little things like a bad fan clutch, or a stuck stat. I replaced both heads on a supercharged 3.8 chasing down an overheating and loss of coolant issue. Turns out it was a leak at the throttle body and a lower radiator hose that was gunked full of stop-leak.

What gets me is that it overheated before, so you re-did the head gaskets and it still overheats. The chances that you have the same exact type of overheating issue after two different attempts of putting on the heads would be rare. I think the problem is elsewhere.

Did you mix 'n match any pulleys for this build? Underdrive pulleys perhaps? They will slow down the water pump if you get the wrong ratio and that can be a problem.

[j cAT]

Originally Posted by 93nitemare

it was a running vehicle with a fresh 347 stroker motor with about 1000-1200 miles on it. then one day it overheated to about 240 degrees. i pulled the heads and took them to a cylinder head shop to get them pressure checked and checked for warpage. the pressure test was good and they were only warped .003 so they shaved off .005.

i got a new set of head gaskets, torqued all the bolts in sequence and to spec as per the sevice manual. drove the car 4 miles and it started to creep up again to about 215 before i shut it down. towed it home and started looking into it and analyzing the situation.

it has a new thermostat. when i start the car in my garage within a minute or two the upper radiator hose gets hard....which should not happen that quick. i tested this on my other mustang i just recently got rid off. i started it and ran it for a few minutes and the upper rad hose was still easy to squeeze and the temp gauge had not even budged.

does napa, advance, autozone, etc. have a combustion gas tester?

take the radiator cap off and see if the coolant is flowing //if this is possible.../no air bubbles in it...

bad thermostat new is very possible////also a missing belt for water pump...seen that before ...funny story...

then theres the water pump that had the impeller not rotating...bad pump..

240deg f is the danger zone....this is not good..