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Dan, Auto Technician
Category: Chevy
Satisfied Customers: 3490
Experience:  GM Mark of Excellence/ Service Guild Participant with 13 years experience, ASE Master Certified
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I have an oil leak on a 2002 Chev Trail Blazer (50,000 ...

Customer Question

I have an oil leak on a 2002 Chev Trail Blazer (50,000 km). It is difficult to see exactly where it is leaking -- but it appears to be at the rear of the engine. Do these engines have a weak rear seal? Where else should I be lokking?
Submitted: 9 years ago.
Category: Chevy
Expert:  Dan replied 9 years ago.
HiCustomer Thank you for asking your question on Just Answer. The other experts and I are working on your answer. By the way, it would help us to know:

-What year is your Chevy?
-What model is your Chevy?
-How many miles are on your Chevy?
-What type of engine is in your Chevy?
-What have you already tried?

Thank you again for trusting us with your problem. Please reply as soon as possible so that we can finish answering your question.
Customer: replied 9 years ago.
Reply to Dan's Post: 2002 Chev Trail Blazer. 30,000 miles 4.2 litre V6.

It is engine oil / drips a few drops after every time it returns to the garage.
Expert:  Dan replied 9 years ago.

I would add engine oil dye and drive the truck for a week. Then blacklight the engine looking for the tracer dye. I did find this bulletin pertaining to the oil sender leaking.

Subject:Oil Leak at Oil Pressure Switch (Apply Sealant) #02-06-01-033 - (10/14/2002)


Models:2002 Chevrolet TrailBlazer

Subject:Engine Oil Leak at intake Gasket - Possible Internal Cylinder Head Porosity - keywords manifold PCV repeat seal #PIP3590 - (10/14/2005)


Models:2004-2006 Buick Rainier
2002-2006 Chevrolet TrailBlazer
2002-2006 GMC Envoy
2002-2004 Oldsmobile Bravada
2005-2006 Saab 9-7x
with 4.2L Engine (VIN S - RPO LL8)


The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.


On rare occasions, an engine oil leak may be noted just below the PCV port between the number 3 and number 4 intake manifold runners. This may be due to oil that settles in the bottom of the intake manifold due to an internal porosity concern with the cylinder head that can cause oil to enter the PCV system.


If the SI diagnostics do not isolate a cause for the above leak, inspect the engine for excessive crankcase pressure by using a manometer and check for restrictions in the PCV system. If there is no problem found, replace the cylinder head for evaluation.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.


2002 GMC Envoy

2002 Oldsmobile Bravada

with 4.2L Engine (VIN S -- RPO LL8)




Some customers may comment about oil spots on the driveway or an apparent oil leak. Upon investigation, the technician may find that the leak is coming from the area of the oil pressure switch.


The cause of this condition may be due to an incorrect type or application of sealant.


Remove and re-install sensor with new thread sealant. When re-installing an existing sensor or installing a new replacement sensor, the technician should be sure that the threads are clean and dry. Apply sealant to the threads in the following manner:

Apply a consistent coating across at least three full threads.
Do not apply any sealant to the first full thread.
Do not apply any sealant in the area of the O-ring seal.

Notice: Failure to properly apply thread sealant may lead to repeat leaks or the failure of the oil pressure switch.

Parts Information

Part Number




(Canadian P/N 10953489)

Thread Sealant - Loctite STS GM6124M


Parts are currently available from GMSPO.