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Ask Gm Tech (Cam) Your Own Question
Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1693
Experience:  GM Grand Master Technician 2007. 14 year experience.
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I have replaced the head gaskets on my 2001 Chevy Silverado

Customer Question

I have replaced the head gaskets on my 2001 Chevy Silverado with the 5.3L engine. I checked the heads for warpage and found them to be within tolerance. I used new head bolts. The engine is now overheating even without a thermostat. I have a new radiator cap on. I have pressurized the cooling system and it held pressure for more than 10 minutes. I depressurized the cooling system and kept the pressure testing gauge attached. I started the engine and monitored the gauge for over pressurization and spikes, which I found none. How do I fix this problem?
JA: Have you checked the coolant? Have you checked for a leak in the cooling system?
Customer: It is full of coolant. I have pressurized the cooling system and it held pressure for more than 10 minutes
JA: Are you fixing your Silverado yourself? What have you tried so far?
Customer: I am doing the work myself. I have used new head gaskets, new head bolts.
JA: Anything else you want the mechanic to know before I connect you?
Customer: I have replaced the thermostat, radiator cap
Submitted: 4 months ago.
Category: GMC
Expert:  Tim Mohr replied 4 months ago.

Hi, my name is ***** ***** you have the heads resurfaced, before reinstalling them?

Customer: replied 4 months ago.
I removed the old gasket material and checked the heads for warpage and they were within tolerance
Expert:  Tim Mohr replied 4 months ago.

ok, but they should always be resurfaced so the new gasket will seal, have you had a black test done on this yet?

Customer: replied 4 months ago.
I pressurized the cooling system and it held pressure for more than 10 minutes. I released the pressure and kept the gauge in place and started the engine. The pressure built up to 15psi and it never spiked like it would if the head gaskets were leaking. What is a black test?
Expert:  Tim Mohr replied 4 months ago.

A block test checks for exhaust gases in the cooling system, it consist of a tube that pour a blue fluid in, then run the vehicle and draws air from the radiator, if the fluid turns green, then it has exhaust gaes in, indicating a head gasket or a cracked heqad or block,Tim