Medium and Heavy Trucks
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Sorry about long delay
Besides disconnecting compressor discharge line also drain all air out of air tanks and recheck for pressure in cooling system with line off and tanks empty. If you can also remove the coolant lines from compressor and plug for testing.
If you need more assistance I will need engine model number and serial number please?
Does this happen all the time or only under a load?
Let me know
The air compressor needs to be cooled and it should have a cooling line on each side of compressor head in.out/
Most times when its the head,head gasket,turbo,ect that allows air to enter cooling system it only happens under a load or is a small amount
since this is happening all the time it's most likely air getting into cooling system.
You did not give me a make and model of truck but some trucks use items like a positive water shut off valve that is air operated when they go bad you get air in cooling system all the time.
Doing what I suggested earlier will eliminate this as a cause or confirm that is the problem.
If you want to talk on the phone let me know its only $10 and we can go over everything at once
I Have some errands to run be gone for a few hours will check back when I get back
I'm just following up to see if we resolved the issue, what it was ,or if you need more info.I would appreciate a reply so I know you are happy with my assistance.Thanksspanky