Author Topic: Cat C9 blow by/oil leak  (Read 2944 times)

Dale Malquist

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Cat C9 blow by/oil leak
« on: May 19, 2021, 06:01:28 PM »
At my local RV repair facility I pointed out the oil splatter on the back of the coach. They say its coming from a broken tube that is the crank case ventilation. They refer it as the slobber tube. Facing the front of the engine it is on the right side.
They claim it it is an extensive job and do not want to do it. Apparently my only option is to take it to the Cat dealer 90 +/- miles over to Las Vegas.

Steve Huber Co-Admin

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Re: Cat C9 blow by/oil leak
« Reply #1 on: May 19, 2021, 10:08:33 PM »
Dale,
You may be able to use a section of heater hose to route the "tube" to the bottom of the engine.
Steve
Steve
Coachless
2015- 6/24  07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Eric Maclean

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Re: Cat C9 blow by/oil leak
« Reply #2 on: May 19, 2021, 11:57:18 PM »
Dale
Have you monitored your oil consumption?
How much oil are you going through

There are several causes for oil Laden draft tube discharge such as oil over full , there is also a screen arrangement in the draft tube collector which is supposed to separate oil from the blow by before it gets to the draft tube or dumped over board.

The draft tubes purpose is to allow combustion gasses which have blown past the piston rings to vent to atmosphere rather than building crank case pressure which would damage seals and gaskets. Hence the name b!ow by.
As piston rings wear out blow by increases the true measure of excess blow by is crank case pressure most manufacturers have a specification for maximum crank case pressure.

Unless your engine has high mileage or been run with a bad or no air filter ( dusted) has been badly overheated or has had poor maintenance ( sludge buildup blocking drain  back galleries) or has sat for a period of time causing rust build up on cylinder walls which inturn causes stuck piston rings.
All of which are unlikely causes of excessive blow by on a normal motorhome engine.

My advise would be to remove and service ( clean ) the whole draft tube and screens reinstall and hang a soup can from the end of the draft tube to collect the oil so you can see exactly how much oil is being expelled.

Good luck
Eric
1997 Patriot Yorktown
3126-B
2009 Chevy HHR
Roadmaster falcon tow bar
Demco Air Force one tow brake.

Dale Malquist

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Re: Cat C9 blow by/oil leak
« Reply #3 on: May 24, 2021, 03:24:15 PM »
The RV repair shop is, apparently, unfamiliar with the Cat. They think it is a major job to repair the tube. They said everything on the side of the engine had to be removed to get to tube. They won’t attempt the job.
Could you please explain how the service is accomplished? Can this service be done by accessing it through the hatches in the bedroom?

Eric Maclean

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Re: Cat C9 blow by/oil leak
« Reply #4 on: May 24, 2021, 05:57:17 PM »
Dale
https://youtu.be/xUY45wGWb-g

This is a u tube link to a C9 breather replacement to give you an idea of removal.

Most shops don't !Ike to work on RVs simply because of the inaccessibility of the engine making them hard to work on .
A good Day dealer should be able to diagnose your blow by using a tool which measure's the amount of blow-by exiting the draft tube as shown in this video.

https://youtu.be/DQ4fgUJJPN8

Hope this helps
Eric
1997 Patriot Yorktown
3126-B
2009 Chevy HHR
Roadmaster falcon tow bar
Demco Air Force one tow brake.