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Old 10-08-2012, 12:11 PM
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Cooling system pressure test

At the risk of on this subject, I need help interpreting the results of this. My gauge showed indication of classic head gasket failure; it would spike up to about 20 psi under hard acceleration and settle down to 16 psi at cruising. That tells me obviously that system pressure went up in correlation to boost pressure, then settled down to the set pressure of the degas cap.

So, here are some other observations and factors to consider:

1) I see no white smoke or coolant at the tailpipe.

2) Engine runs very smooth and strong (no indication of combustion issues due to coolant in cylinders)

3) Pressure does not drop when engine is shut off (except slowly over several hours)

-On this point, if combustion gasses were entering the cooling system when engine is running, would it not also be that coolant would enter the cylinder(s) when the engine is shut off? There seems to be no indication of that in my case, which leads me to my next question: Is there a possibility of pressure building in the system from the intake (boost) side? I haven't done the test for combustion gasses in the coolant reservoir yet, and that seems to be the logical next step, but the coolant and reservoir are staying clean. I want to rule out any other possibilities before I tear into doing head gaskets. Any insight would be appreciated.
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Old 10-08-2012, 12:52 PM
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The best test for combustion gas is either the test strips or the tester with the colored chemicals. If it is heads or egr cooler it will have to have combustion gas in the coolant.

No combustion gas no head gasket or egr cooler failure period.

Your pressure issue is then one of the other possible causes, coolant overheat causeing extra exspansion of the coolant along with possibily overfull of coolant to begin with.
Pump cavitation can also add some pressure. A bad cap that doesn't vent at 16 psi is also possible.
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Old 10-08-2012, 01:42 PM
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Coolant level is kept low - 1/2 inch below min. mark at full operating temp. I'm not having any coolant loss at this level.

ECT is steady at 189-190

The pressure increase on gauge is in direct proportion to throttle input.

At idle, the pressure is steady at 16 psi. That tells me the cap is good. The cap is irrelevant in this case because the pressure shouldn't be going above 10 or 12 psi anyway.

on edit: EGR is deleted
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Old 10-08-2012, 04:03 PM
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Anybody else have any input?
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Old 10-08-2012, 05:52 PM
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Normally with head gasket issues you won't have any excessive white smoking out of the exhaust. Also most times the engine will run perfectly fine with blown head gaskets. As the leak gets worse and worse it will start to push coolant out of the bottle. As far as leaking back into the cylinders when not running think of it like this. You can have a very small head gasket leak that will let the 350+PSI of compression leak by, yet it's not big enough to let the 16 psi of coolant pressure push anything through the head gasket after you shut it off. Make sense? In my opinion you definitely have the start of a head gasket leak, especially since you've already deleted the EGR. Really there isn't much else it could be. Sorry for the bad news!
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Old 10-08-2012, 06:19 PM
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^^ I agree completely with this. Mine did the same exact thing as yours is doing now and I already had my egr deleted. Once I tore it down I found that the left bank had blown the gasket between 4 and 6 and was working on getting through from 6 to 8. Passenger side was fine not a single leak. My truck otherwise ran like a raped ape never any white smoke or coolant in the exhaust and barely puked at all until more recently before I ripped it apart for gaskets and studs.
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Old 10-08-2012, 09:32 PM
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Quote:
Originally Posted by justinmix View Post
Normally with head gasket issues you won't have any excessive white smoking out of the exhaust. Also most times the engine will run perfectly fine with blown head gaskets. As the leak gets worse and worse it will start to push coolant out of the bottle. As far as leaking back into the cylinders when not running think of it like this. You can have a very small head gasket leak that will let the 350+PSI of compression leak by, yet it's not big enough to let the 16 psi of coolant pressure push anything through the head gasket after you shut it off. Make sense? In my opinion you definitely have the start of a head gasket leak, especially since you've already deleted the EGR. Really there isn't much else it could be. Sorry for the bad news!
Yes, that does make perfect sense. I guess I'll start ordering parts. I am looking at a stud/gasket kit that uses Black Diamond HG's. Are these recommended? They are supposedly the same as OEM.
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Old 10-09-2012, 01:04 AM
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Sounds like HGs.. Just get OEM gaskets since they have been tested over and over with great results along with ARP studs. If you want to save a few bucks then try the new gaskets that are on the market and let us know how they work out for you. I would rather pay a extra $200 for peace of mind.
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Old 10-09-2012, 04:48 AM
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Personally I'd stick with OEM head gaskets. You pay a little more for the parts up front but there are much less repeat failures with them. Also make sure to get the heads checked out. in my experience 95% of the time they will need to be milled.
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Old 10-09-2012, 04:54 AM
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The parts guy said these gaskets are the same as oem, with an updated coating so they're black instead of blue. They even have the same numbers stamped on them. He said they're way different than Black Onyx.
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