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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29495
Experience:  GM Grand Master Technician 2007. 14 years experience.
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My 2005 Chevy Duramax has too much pressure in the cooling

Customer Question

My 2005 Chevy Duramax has too much pressure in the cooling system. We have replaced the Radiator cap with OEM, thermostats with OEM, head gaskets with OEM then felpro gaskets and the studs with ARP studs. It is still building too much pressure in the cooling system. When the head gaskets where taken off 2 of the head bolt studs at the back of the head on the passenger side and 2 of the head bolt studs on the front head on the drivers side were loose. Both heads were inspected for cracks. All cylinders were inspected as closely as possible with the block still in the truck. After every thing was put back together it still is building pressure and the cooling system dumps coolant. What could we be missing.
Submitted: 1 year ago.
Category: Chevy
Expert:  Greg Jensen replied 1 year ago.

Have you checked the EGR cooler?

Customer: replied 1 year ago.
we have and it is working ok.
Expert:  Greg Jensen replied 1 year ago.

Sorry I should have said that differently, have you pressure checked the cooling side of the egr cooler. We have a tool for it in the dealership but with a few hoses you can make one and use your coolant pressure tester.

Expert:  Greg Jensen replied 1 year ago.

I have seen several of them leak.

Expert:  Greg Jensen replied 1 year ago.

internally and can be hard to pin point.

Customer: replied 1 year ago.
We completely by passed the egr and the cooler and it still did it. So it can not be the egr system.
Expert:  Greg Jensen replied 1 year ago.

That was my only idea at this time, I'll opt out and see what others my have for you. If anything else comes to mind, I'll check back in. Good luck.

Expert:  GM Tech (Cam) replied 1 year ago.

Hi there, I am Cam. Can I get your first name pleasE?

With your truck, did you check the heads for being warped?

Expert:  GM Tech (Cam) replied 1 year ago.

??

Customer: replied 1 year ago.
we checked the heads and the block for warpage.
Expert:  GM Tech (Cam) replied 1 year ago.

Ok, if idling, do you get any bubbles after idling? TO get that kind of pressure still suggests head gaskets.

Customer: replied 1 year ago.
No we do not get any bubbles. We replaced the head gasket with a factory and still had problems. So we replaced it again with a Felpro gasket.
Expert:  GM Tech (Cam) replied 1 year ago.

Ok, so to get pressure like that in the cooling system can only be head gaskets or heads. Now I will admit I a have not seem many heads with issues, but its possible. You checked out warpage, did you have them pressure tested by a head shop?

Customer: replied 1 year ago.
I am unsure of them pressure testing at the machine shop.
Expert:  GM Tech (Cam) replied 1 year ago.

Did you check the deck for warpage? Also what happened originally? Did it overheat? Let me also check a couple other things. Give me 10 mins.

Customer: replied 1 year ago.
The first thing that happened was the connector for the fuel injectors went bad. We were on a vacation and loaded with our camper. It has overheated several times. It did have 2 blown head gaskets, but not too bad. It was starting to hydro lock when we pulled it into the shop to do the head gaskets. It had sat in the driveway for a couple of weeks waiting for us to have time. Now it is building too much pressure in the cooling system within 4-5 minutes of running. We have to be missing something in the process.
Expert:  GM Tech (Cam) replied 1 year ago.

If it overheated in the process and hydrolocked, that is bad. Its very possible there is a bit more damage in the engine. How long did you run it when checking for bubbles? Did you bring the idle up?

Customer: replied 1 year ago.
We have ran it for several minutes then it starts pouring out the coolant from the system. At that point you can not do anything but shut it down. We just bumped it over when it was hydro locked. It does not have a bent rod or any noise from the lower end.
Expert:  GM Tech (Cam) replied 1 year ago.

No and doubted it damaged lower end, but combustion chamber is my concern. TO push out like that can only be cylinder so we missed something in there. I am thinking you need to have the cylinder heads pressure tested, check deck warpage and likely replace the heads.

Customer: replied 1 year ago.
Sorry I did not get right back to you. We pressure tested the engine and let it sit with pressure for 6+ hours. There was no coolant on the plugs.
Expert:  GM Tech (Cam) replied 1 year ago.

The issue is though that the amount of pressure it takes to push coolant into the cylinders is more than you can get in the coolant system without doing damage.

Customer: replied 1 year ago.
Cam,The strange thing about this is when we did the first head gasket it ran back and forth to work (about 6 miles each way) for 4 days. Then on the night of the 4 day we took it to a meeting about 40 miles total was put onto it. On the way home he got onto it just a bit, nothing too hard. The next morning is when it starting acting like the head gasket was blown again. It just builds too much pressure in the cooling system then blows it out. We checked the heads and the block for warpage with a straight edge. We did block off the egr system to make sure that was not it. Could the turbo or something in the exhaust be doing this?
Expert:  GM Tech (Cam) replied 1 year ago.

To build pressure like that in the cooling system, no. The only thing I have ever seen cause it to build that much pressure is the heads.