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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8723
Experience:  I am ASE Master Truck Certified.
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My 2006 gmc 7500 truck with 6 cyl cat motor all of the

Customer Question

hello. my 2006 gmc 7500 truck with 6 cyl cat motor all of the sudden is blowing oil out the breather tube. 5 gals in 6 miles. idles rough but clears up with increased RPMs. has good power. any ideas
JA: What is the complete model and serial number of your machine?
Customer: it is a 2005 c7c, 6 cyl. vin 1gdj7c1c55f514503
JA: Anything else you want the equipment mechanic to know before I connect you?
Customer: no
Submitted: 7 months ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 7 months ago.
Thanks for asking your question. I will try and help you out.
There are three things I have seen cause this.
The first and most common is a failed or gaulded cylinder. Sometimes the spray pattern of an injector can wash done a cylinder and cause high blow by.
Second is a failed turbo. They can fail and put exhaust down the oil drain tube and push out engine oil
Lastly is a worn air compressor. They have pisotns to and can wear and increase crankcase pressure. However since you are pushing out a lot of oil. I would not suspect the air compressor.Please reply back if you need more help or have more questions. I am happy to assist.
Customer: replied 7 months ago.
is there a way to test the turbo?
Expert:  Cat Man replied 7 months ago.
A faulty turbo will only push out oil when the engine is under load and making boost pressure. So I like to rev the engine to high rpm and monitor the blowby tube. If you see oil being pushed out at high idle and no boost. I would suspect a cylinder problem. If you see no oil at high idle. It must be coming out under load so I would suspect the turbo.
Please reply back if you need more help or have more questions. I am happy to assist.
Expert:  Cat Man replied 7 months ago.
Hey. I just wanted to see how things were going. Please let me know if you need more help. I am happy to assist. If my information was helpful, please leave a good or higher rating so that I receive credit. Thanks.

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