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I need some help with some pressure readings I am getting from my cooling system. To start I have around 7pisg when up to temp and idling. If I drive around and stomp on it, the pressure goes up to about 15-17 then drops back down. I'm of afraid of the answer to the next question (but I think I now what it is). Does it sound like it could be my head gaskets? It definitely isn't the EGR cooler, it's welded shut. Also, it isn't losing coolant or puking.
That’s what mine did with two leaking head gaskets. Combustion gas gets into cooling system and the degas bottle does it’s job by releasing pressure at 16-18psi. Mine would only puke if the coolant level was over the max fill mark and I really romped it hard.
It looks like what might be happening is the cap is releasing and that is why the pressure drops. I did have it sit for a couple hours and it still had a few pounds of pressure.
I guess since it is head gaskets I'll just replace the heads while I am at it. I don't know of any machine shop around me to check them. And with all the potential issues, I'm leaning towards a set of KDD heads. I emailed them and they have a kit that includes heads, fel pro gaskets, arp studs, and a fel pro top end gasket set. It seems like a good start. Any other ideas of what to look at or replace while in there.
Also, Jack I just watched your video on your block surface prep. WOW. But it did give some great pointer.
Good point about the cap, this weekend I'll go to the local O'Reilly's and get the loaner cooling system testing kit. Will check both the cap and system. Also, I will do a bubble test and test for combustion gases in the coolant.
I don't want to give you false hope or wishful thinking but even with a welded cooler there is a chance of boost pressures or exhaust drive pressure leaking in the cooler and bleeding into a cracked cooler's coolant side.
Thanks about the info on the cooler, but it is welded shut at the up pipes and both ends of the cooler. Also pressure tested the cooler afterwards, and had no leaks. But I can add it to the list to check. That would be much easier to fix then heads. (But definitely not getting my Hope's up on that)
Quick little update, first the cap does leak slowly. With the tester it got up to 16 psi then relieved, then continued to drop slowly. After a couple minutes it was under 9 psi.
I pressurized the cooling system, and after 10 minutes it went from 15 to around 14.5 psi.
Now I was also able to do a bubble test and now I am confused by my results. The truck was up to temp reading 192 ECT while I did the test. At idle I had no bubbles. I let it run for about 5 minutes. Then I went to high idle and after a couple of minutes I started getting bubbles. So I unplugged the VGT on nothing changed with them. Now my results get strange, I turned off the high idle and the bubble disappeared. I reconnected the VGT no bubbles, still, turned the high idel on again still no bubbles. Redid the bubble test and I am getting a slow steady stream of bubbles at idle.
This afternoon to test fluid comes in to the part store, so I am going to test for combustion gases.
But as of right now the only definite thing I have found was a leaky cap. To be replaced.
Last edited by Motohead911; Aug 27, 2019 at 01:26 PM.
Reason: Bubble test results changed
Sounds like head gaskets to me. You shouldn’t see more than 8-10psi coolant pressure at any time and that is only due to thermal expansion of the coolant.
Now I have a few more questions.
1 would a leaky head gasket cause the issues I had while I was towing a couple weeks ago. I had fine temps for an hour or so, then the temps were all over the place.
2 I guessing i have a small right now, since I don't have the classic symptoms. No puking, no coolant, no real overheating.
3 is there any thing else I should look at or just get ready to do the gaskets?
I had both head gaskets leaking by and it would hold about 12-15psi normal driving but when I would romp on it even a little it would vent off at 16-18psi. Combustion gas is hot and yes it will introduce additional heat into the cooling system. I recommend UCF o-ringed heads and Mahle or Motorcraft head gaskets. Stud it while you’re in there and if possible clean the block yourself WITHOUT using any air tools. you probably have the (from what I’ve researched) compromised head gaskets between bores and the combustion gas is leaking into the cooling passages when it gets a chance. This will only get worse so I’d take care of it as soon as possible. I drove mine very lightly for over 30,000 miles and was lucky the gaskets didn’t completely let go and leave me stranded or compromise my engine. https://ucfmachineshop.com/
If you're buying new heads I would do Kill Devil and not UCF, for the simple fact your heads are "probably" ok but if they're junk you are out 350.00 per head.
Now add the cost of the UCF heads and it gets expensive quick. Jared from KDD is a stand up guy and has GREAT luck with his heads and machine work. Mine have been flawless for a few years, along with many people on this forum.
Whichever decision you make, I am sure you will be happy to have a solid truck
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