Do I really need to remove carbon and adjust valves on my Onan P218

[Steffen_Brandt 39]

Hi everyone

 

So heres the deal.

 

I bought my 518 H back in 2012. At the time it had 2000 hours+ on the clock.

Today it has 2180 hours on the clock. The maintenance schedule says, that I have to remove carbon from the heads every 1000 hours.

So not knowing if the PO owners have done this, I think it is time to do something about it and at the same time adjust the valve clearence.The engine is running okay, so I thought I would start by cheking the compression of each cylinder. Each cylinder reads 125 PSI. My manual says 115 PSI.

 

How should I react to this?

Does it mean that the valves are seating just fine?

Does the higher (than 115 PSI) compression mean, that there are carbon deposist, making the volume in the cylinder smaller, thereby increasing the pressure?

Is my engine just okay, and there is no reason to take it apart to adjust the valves and remove carbon?

 

Thanks!

[slammer302 2,154]

I would take the front head off and take a look then you will know what's going on in there pretty much everyone I've opened needed it and it gives you a piece of mind I will say that I've opened sum up that run great and look horrible inside the head and the top of the piston be worn away from carbon build up and the valves caked with carbon too so what I'm saying is you can't unsee sum things.

[Coadster32 793]

Not too sure I'd try to fix what isn't broken. If you wanted to, you could spray sea-foam in the carb while it's running as well, (will smoke like a banchee). Most guys who use it, swear by it. They'll typically empty a whole can of it in one episode. I have done this as well, but without a real problem, hard to say if it really works. 

[boomers_influence 106]

steffen

i would recommend doing the de/carbon job.

AS A RULE,

the de/carbon job also includes

adjusting the valves.

thank you. boomer ( the used onan engine parts guy )

[smoreau 658]

steffen

i would recommend doing the de/carbon job.

AS A RULE,

the de/carbon job also includes

adjusting the valves.

thank you. boomer ( the used onan engine parts guy )

I couldn't agree more than this! Main thing is adjusting the valves, not the decarbon, you just do a decarbon while you have the stuff off. Valves will need to be adjusted and if you don't it will shorten the life of the engine.

[boovuc 1,090]

  YUP! 

[Steffen_Brandt 39]

Thanks for all the replys. .

So I am going to decarbon the engine and adjust the valves. I wonder how much carbon I will find in it. Any ideas on the best way to remove the carbon? Steelbrush?

Thanks!

[boovuc 1,090]

Hi Steffen,

 

I used thick rubber gloves, great ventilation, a 3M scotch pads, (dish scrubber), with Acetone. To get into and around the valves, I used soaked Q-Tips, (cotton swabs), dipped in Methyl Ethyl Ketone and kept soaking the deposits then rubbing with more cotton swabs or a pipe cleaner. This will take 90% of the deposits off the heads, cylinders and chamber areas. The valves and seats are time consuming and I did have to rub hard deposits with a slim plastic pick repeatedly.

Make sure you work on each jug with the head of the cyl flush and run a ring of heavy grease or Vaseline around where the cylinder and the cylinder wall meet to keep debris from falling in between and damaging the rings. 

 

If you search here or maybe on YouTube, there may be more info on doing this bit of required maintenance.

[MAH 50]

I will be swapping engines from one tractor to another this spring. The engine has about 500hrs on the meter which I believe there is a maintenance interval to remove the heads, decarbon and adjust the valves. I don't have an engine manual in front of me at the moment but I believe it is every 500. Anytime I remove cylinder heads I always blow some air around the cylinder walls and pistons and inspect it with a flashlight to make sure the junk is out, just before reinstalling the head, you don't want to go through all that work to break a ring and have to rebuild.

If you pull the engine you can remove the cylinder head and stand the engine up so you can soak the cylinder (I would imagine a spray bottle and a continuing light spray bottle o keep this soaking would work as good), at work I use brake clean which is basicly acetone, for a few minutes and clean it out with a rag. Blow out anything left use a clean lint free rag when its all clean and coat the cylinder wall with a light coating of oil.