John Deere F735 Diesel Help Please

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engdavis
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John Deere F735 Diesel Help Please

Postby engdavis » Fri Apr 26, 2013 1:03 pm

Hi All. I'm new to the group and I hope someone here can help me out with my John Deere F735 Front Mower engine problem.

My John Deere F735 (Yanmar V-Twin Water Cooled Diesel with 592 hours on it) has me baffled. When I bought it it wasn't running and had been sitting for several years. I found the fuel tank, lines and filters were clogged with thickened diesel fuel so I took the fuel system apart and cleaned everything. The injection pump and injectors were also extremely stiff from old fuel and I had them professionally cleaned and adjusted. The mower now runs very well but it is constantly leaking oil from the valve cover gaskets (both cylinders). I checked the PCV valve and cleaned it so I know it’s working as it should.
In troubleshooting the problem I removed the PCV lines from both valve covers and ran a piece of clear plastic hose from each valve cover to a bucket. I thought I could at least isolate the problem to determine if one of the head gaskets may be bad and causing over pressure in that cylinder. Unfortunately it wasn’t that easy. The hoses from both cylinders are acting exactly the same. When the engine is first started everything is clear and neither cylinder is blowing more than the other. Then after about a minute or two both sides start sending engine oil down the tubes. Apparently the valve covers fill with oil to lubricate the valves and rockers and both started this at the same time so I suspect it’s supposed to be that way. My question is why? Surely there must be some mechanism that prevents pumping oil through the PVC lines into the intake manifold. I think too much pressure is building up in the lines and it’s somehow forcing oil past the valve cover gaskets. I’ve taken off all the PCV lines and checked them to make sure none of them are clogged and they are all clean and open. When the engine is running it builds up quite a bit of pressure in the lines and I think that may be why the valve cover gaskets are leaking, but I don’t know how to stop that.

I replaced the valve cover gaskets yesterday but I still have the problem. While I had the valve covers off, I checked the oil return ports and they are open and clean. Does anyone have any idea how I can stop this oil leaking out the valve covers? Is it normal for oil to be in the PCV lines? There is just a small amount of pressure pulsating out of the lines when the engine is running so I can’t figure out how it is building enough to force oil past the valve cover seals.

Any help or advice would be greatly appreciated.

Thanks,
Mike

winston
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Re: John Deere F735 Diesel Help Please

Postby winston » Fri Apr 26, 2013 3:22 pm

Do you think the rings are ok with not much blow by? A lot of blow by could cause what you are experiencing. Is there a crankcase vent other than the pvc valves?

After looking at the John Deere parts pages for this mower I can't find the pvc valves you are talking about. I did find a reed valve in the intake manifold. Have you checked it?

engdavis
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Re: John Deere F735 Diesel Help Please

Postby engdavis » Sat Apr 27, 2013 7:57 pm

Thanks for the reply.

I too suspect the rings. Even though it has less than 600 hours, I don't know the maintenance history and the symptoms are consistent with blow by. I'm just trying to make sure I look at everything else before I tear into the motor.

The JD Parts website doesn't do a good job of identifying the parts until you actually put them in your cart, then the definition shows up more clearly. The PCV valve is on the top of the motor and is nothing more than a metal box with a reed valve in it. Very simple. The output hose from it joins two hoses from the valve covers and they all dump into the intake manifold. I haven't seen any kind of reed valve in the intake manifold.

PaulW
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Re: John Deere F735 Diesel Help Please

Postby PaulW » Sun Apr 28, 2013 3:28 am

have you tried a much thinner oil in it so it runs away to the sump quicker?
Paul W YM1500 & YM14 MkII

winston
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Re: John Deere F735 Diesel Help Please

Postby winston » Sun Apr 28, 2013 6:04 am

Yes, my bad, the parts drawing was entitled "intake manifold" but you are right the reed valve in in it's own little box. If you pull the pvc line off the head while the engine is running and you are getting a big blow with oil that could help determine. Might have to stop up the entrance to the valve cover. Sound stupid?

Another remote possibility is the valve stem seals are bad.

Norm
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Re: John Deere F735 Diesel Help Please

Postby Norm » Sun Apr 28, 2013 8:47 am

How sure are you about the hours, considering sitting for several years? Does it have a 999.9 or 9999.9 meter?

engdavis
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Re: John Deere F735 Diesel Help Please

Postby engdavis » Mon Apr 29, 2013 1:32 pm

I've thought about the valve seals but have pretty much ruled them out since their primary function in life is to keep the oil out of the combustion chamber. My problem is too much oil (or pressure) in the valve cover so that's before the seals and if I had a bad seal it should be smoking blue and consuming oil. My problem is that it's not burning oil but leaking it from the valve covers so a bad seal doesn't really make sense to me.

I'm pretty confident the hours are correct since there is very little cosmetic wear or damage to the machine. Even the deck is not scuffed up as you would expect if it had 6000 hours on it. The condition of the valve train is also very clean and doesn't show any signs of wear which is consistent with a machine with this number of hours on it.

I'm using straight 30 weight JD oil in it because that's what the owner's manual calls for when temps are over 85 degrees Fahrenheit. I've thought about trying 15W 40 diesel oil but haven't gone to that yet.

Everything I'm reading points to blow by but I'm wondering if the rings could just be stuck. I'm going to try several "low hour" oil and filter changes with a little Marvel Mystery Oil added to see if the detergents in the new oil/Marvel mix might break them free. Parts alone for a ring job would run about $300 so I'm trying to avoid that expense until I've exhausted all other less expensive alternatives.

Thanks for all the ideas though. I appreciate your help.

PaulW
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Re: John Deere F735 Diesel Help Please

Postby PaulW » Tue Apr 30, 2013 2:59 am

engdavis wrote:
I'm using straight 30 weight JD oil in it because that's what the owner's manual calls for when temps are over 85 degrees Fahrenheit. I've thought about trying 15W 40 diesel oil but haven't gone to that yet..



I think that may be your problem, the oil cold wont drain as quick as when it is hot. i would try even a 5w/40 in it and see how it goes
Paul W YM1500 & YM14 MkII

Norm
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Re: John Deere F735 Diesel Help Please

Postby Norm » Tue Apr 30, 2013 8:00 am

If hours are correct it likely is stuck rings. I would add about a pint of ATF, (Dexron), to those oil changes. Works great for cleaning engines and lubes well. Change when oil turns black.

doggy
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Re: John Deere F735 Diesel Help Please

Postby doggy » Tue Feb 18, 2020 12:09 pm

Hello, a old post but have problems with my JD f735 also.
my first post and im from Sweden so my english can be bad sometimes..:)
Anyway did you resolve your problem with overflow oil?.

doggy
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Re: John Deere F735 Diesel Help Please

Postby doggy » Sun Mar 15, 2020 2:46 pm

I have almost the same problem, pushing oil from pvc hoses on the valve covers, only 211 hours on engine, have been sitting for many years.
i dont know what is normal blowby..:/


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