2001 gmc sierra 4.3 vortec v6 no coolant pressure

[2001gmcsierrav6]

hey guys, I know testing has to be done to figure this out, but i wanted to ask about the 4.3...... i was told it has a tendency to go through intake gaskets, is that true? this truck only has 87k miles and runs like a top, no oil contamination or anything like that. When i squeeze the upper rad hose there is no pressure though, i can easily squeeze it. no way there's 15 psi in there. Before i jump to thinking it could be a head gasket i wanted to ask about the intake gasket thing.

 

Thanks for any input. Also whats the best test i can do?

 

Cheers.

[sefiroxx]

15psi when hot and circulating. You have air in the surge tank and the air will compress

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[2001gmcsierrav6]

after bringing the engine to operating temp there is no pressure in the rad hoses. also when i remove the cap on the surge tank there is no pressure.....

[rjgti]

bad cap, have it tested

[00Silverado4x4]

On Monday, October 16, 2017 at 11:48 AM, rjgti said:

bad cap, have it tested 

This ^^^^. After all the cap is how the pressure is allowed to develop.

[2001gmcsierrav6]

replaced cap, still no pressure. i will try to drill a hole in the old cap and use the compressor to inject air into the system....see if i cant find something.

 

any other suggestions would be great, thanks. 

 

[2001gmcsierrav6]

put 15 lbs on the system, bleeds off fairly quickly. loses about 5 psi in 5 min.  still cant find anything visual though. been spraying soapy water on everything to try to isolate the leak and still no dice. 

 

im thinking of trying a mirror at the back of the heads/intake area, maybe its back there. 

 

i also put balloons on the oil fill spout, intake and exhaust pipe and none of them filled up, so still pretty sure its not a head gasket.

[00Silverado4x4]

No insult intended but soapy water may not be very helpful to find a coolant leak. You need everything clean & dry then pressure check the system. Also the balloons on the tail pipe won't help as there are preexisting drain holes in your exhaust system.

Did you check over your radiator & connections? With modern radiators being more plastic then before tend to crack easier with age.

However it still could be a head gasket. It could be leaking internally. You will need to get a camera in through a spark plug hole or pull the heads to find out for sure.

[Bob D]

On 10/15/2017 at 1:56 AM, 2001gmcsierrav6 said:

...When i squeeze the upper rad hose there is no pressure though, i can easily squeeze it. no way there's 15 psi in there....

 

Cheers.

Why there should be 15 psig if the temp is below boiling?

Are you losing coolant?

[2001gmcsierrav6]

its intake gaskets, found the leak between the intake and head on the rear passenger side. will tackle it as soon as i can. PITA

 

thanks for everyone's help.

[00Silverado4x4]

Glad you found the problem. Check back when repairs are done. Hope it turns out well.