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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8417
Experience:  I am ASE Master Truck Certified.
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I recieved two C7 engines built brand new in 06 and saw some

Customer Question

i recieved two C7 engines built brand new in 06 and saw some shelf time until i recieved them for the same truckin the last twomonths. both engines have oil coming out of the exhaust manifold. i already checked the turbo's on both engines still brand new and nooil in or coming from the turbos. i checked valve lash just to be safe and allintake and exhaust valves are in tolerance on both motors. the only logical answer would be valve seals. crankcase pressure is also within perameters. i made sure and drained as much of the preservative oil i could then pre lubed with 15/40 under the valve cover given the first motor had thesame problem. it also looks like theres some scoring on the #5 and #6 exhaust valve rods.i wasnt thinking valve seals given that these engines are brand new just saw some shelf time.
Submitted: 2 months ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 2 months ago.
Thanks for asking your question. I will try and help you out.
If the engines have sat for ten years. You may have dryness or rust in the cylinders causing stuck or damaged rings. You are correct the valve seals could be bad and rotted.
How much oil are we talking about?
Have the engines just been started and this was noticed? Or was the truck taken on a test drive it out in service?
Customer: replied 2 months ago.
Enough to make me think there was a engine fire when I was running it in. So a fair amount. We already talked to the facility where the engines came from. Under stable to have dry rot on the valve seals but two engines in a row on top of that I was thinking other manufacurer errors.
Expert:  Cat Man replied 2 months ago.
I see. Thanks for the information.
If there's a lot. I would more suspect a cylinder and ring problem. I would not suspect valve seals as they should only pass a small amount of oil. But a cylinder issue can pass a lot of oil. Looks like the head will need to come off to find out more.
Please reply back if you need more help or have more questions. I am happy to assist.
Customer: replied 2 months ago.
I could see that on one cylinder, but 2 or more doesn't add up. I will get back to you after I remove the head with some other questions
Expert:  Cat Man replied 2 months ago.
Ok sounds good. Let me know what you find and if you need more help.
Customer: replied 2 months ago.
What is the proper cylinder psi for a compression test?
Expert:  Cat Man replied 2 months ago.
Unfortunately Cat does not give out a spec for compression test sorry. I would assume it's around 250-300 psi.
Customer: replied 2 months ago.
is it possible thay there is a timing issue. i would thinkif there was it wouldnt run normal, but it runs great. so is it stillpossible for it tobe valve timing?
Expert:  Cat Man replied 2 months ago.
I would not suspect a timing issue. Especially if it runs great. When cam to crank timing is off the engine will not hardly run.
If valve timing was off. I would think the engine would not run great.
Customer: replied 2 months ago.
if i could get a view of the firing diagram so i can see when everything is supposed to open and close that would help. my coworker seems tothink its odd that the exhaust valve opens as the piston starts to go down and closes as it comes up. seems normal to me but if i could get some clarification or a 4 stoke diagram for the c7 that would be a great help.
Expert:  Cat Man replied 2 months ago.
The engine turns clockwise from the front. The exhaust valve should open as the piston is coming up.
Customer: replied 2 months ago.
That explains it since I hat to turn it counter clockwise at the alternator. Also no oil in the cylinders coming from the intake. I put some fresh oil on top of the #5 and #6 exhaust valves and saw a decent amount of oil on the valve rod. I haven't removed the whole exhaust manifold yet to see if all the valves are leaking or if there is oil on cylinders 1-4. If there is oil present on all exhaust valves is there anything else I can check?
Expert:  Cat Man replied 2 months ago.
Thanks for the information.
Not sure there is anything else. Sorry. Next step would be removing head.
Expert:  Cat Man replied 2 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!

Customer: replied 2 months ago.
I checked the exhaust valves on 3&4 after letting them sit for a day after putting fresh oil on them. When I came to work in the morning oil was pooled on top of the valve so I ordered new exhaust and intake valve seals. I should be able to change those out without removing the head if I bring each cylinder to tdc on the compression stroke right?
Expert:  Cat Man replied 2 months ago.
that is correct. You should be able to do that.
Please reply back if you need more help or have more questions. I am happy to assist.
Expert:  Cat Man replied 2 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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