back pressure

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housebg
Posts: 56
Joined: Sat Feb 18, 2017 10:30 pm
Location: Walker Louisiana

back pressure

Post by housebg » Fri May 05, 2017 7:51 pm

My 880 has a lot of back pressure in the pan not in valve cover , it blows the oil cap off when you crank . I talk with a guy that had some knowledge of the David Brown tractors and he said that it may be the oil pump . Is this possible if so it would be a lot easer to exchange the oil pump . What are your option.

joeproctor
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Re: back pressure

Post by joeproctor » Fri May 05, 2017 8:15 pm

try cleaning the breather pipe that comes out of the rocker box,it may be a good idea to clean the rocker box top and change oil and filters,

housebg
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Joined: Sat Feb 18, 2017 10:30 pm
Location: Walker Louisiana

Re: back pressure

Post by housebg » Fri May 05, 2017 10:39 pm

Did all you said and did not help

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ollek
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Re: back pressure

Post by ollek » Sat May 06, 2017 5:01 am

Sounds like the old story, piston blow by. This has nothing to do with the oil pump. If the tractor has been used for a long time with low rews and loading, then the cylinder walls can be glazed. Try to put the engine some hard work and see what happens.

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bedwards1966
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Re: back pressure

Post by bedwards1966 » Sun May 07, 2017 2:34 pm

Have you removed the gauze filter that's in the top of the rocker cover? They're best removed.

I cannot see any possible way that an oil pump would cause pressure in the sump, it's pumping oil not air. The sump and rocker are connected as oil drains from the top of the engine.

Try giving it some hard work as suggested, some blowby is quite acceptable but obviously there are limits. One thing to look at is how easy is it to remove the dipstick? Some (maybe all) DB's have an O ring on the dipstick, if it's worn or a bad fit then the dipsticks are loose and very easily come out. Make sure that it's a reasonably snug fit.

housebg
Posts: 56
Joined: Sat Feb 18, 2017 10:30 pm
Location: Walker Louisiana

Re: back pressure

Post by housebg » Sun May 07, 2017 6:06 pm

Have removed it and am getting ready to work hard

housebg
Posts: 56
Joined: Sat Feb 18, 2017 10:30 pm
Location: Walker Louisiana

Re: back pressure

Post by housebg » Tue May 09, 2017 11:39 am

It will pop the dip stick out fifteen ft. (three meters) seams to just started . When I bought the tractor it did not do this . It started good also , then it started to be hard to start and have the back pressure. :evil:

joeproctor
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Re: back pressure

Post by joeproctor » Tue May 09, 2017 1:30 pm

thats a lot of pressure,looks like a strip to find the problem,starting with the sump off and head off pistons out ,get a manuel it will help ! come back and tell us what you discover?

housebg
Posts: 56
Joined: Sat Feb 18, 2017 10:30 pm
Location: Walker Louisiana

Re: back pressure

Post by housebg » Tue May 09, 2017 9:41 pm

am going to start slow , :wink: it runs very good when it is running no smoke or any thing

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skyrydr2
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Re: back pressure

Post by skyrydr2 » Wed May 10, 2017 9:03 am

Does it push oil out the dipstick hole? Maybe the stick is bent in such a manor it is getting knocked out by something spinning in the crankcase? (Crank lobe or connecting rod?)
With preasures like that I can't believe it has not blown out a gasket or seal yet?

housebg
Posts: 56
Joined: Sat Feb 18, 2017 10:30 pm
Location: Walker Louisiana

Re: back pressure

Post by housebg » Sun May 14, 2017 6:32 pm

It pop out three ft. . It seams to have started it about a month after I bought it.it does not have back pressure on the top end?

joeproctor
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Re: back pressure

Post by joeproctor » Sun May 14, 2017 10:21 pm

oil drains from the rocker back into the sump via a hole more that one,they cant be blocked because oil would pump up to the rockers and come out of the breather pipe hence if you have piston blow by then all the engine will'breath' not just pressure the sump so much that the dip stick can be blown out,you need to check this !

housebg
Posts: 56
Joined: Sat Feb 18, 2017 10:30 pm
Location: Walker Louisiana

Re: back pressure

Post by housebg » Fri May 19, 2017 11:49 am

what do you suggest that I do I am at a loss. A man in the west US said it could be oil pump. I can't see this but I can't see the pressure like it is. He also said it may be carbon build up on the head. It started very sudden that is what is strange about it. All help is welcome.
Some said it is from setting up and said to add Transmission oil and work hard? :? :? :?

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ollek
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Re: back pressure

Post by ollek » Fri May 19, 2017 3:14 pm

It is NOT because of the oil pump. Why would you have to add transmission oil if the engine have excessive crankcase pressure? The reason is excessive crank case pressure and this can come from glazed cylinder walls, broken piston rings or damage piston(s). Glazing of the cylinder walls can be reduced by working the engine hard and checking the engine oil level during the time the engine is under heavy load. Any other problems involves removing the cylinder head and/or the oil pan. Faulty engine set up will not create crankcase pressure. Sounds like most of the suggestions you have got, are told by people who do not understand the basics around engines. By the way, have you checked and can you confirm that the crank case breather system is not clogged up and is open to the air?

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bedwards1966
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Re: back pressure

Post by bedwards1966 » Fri May 26, 2017 9:13 pm

You say that it didn't do this when you bought the tractor, what have you been using the machine for?
And have you now given it some hard work and to what effect?

Some of the suggestions you have been given are remarkable, and should be disregarded as the people making them appear to have no knowledge or understanding of engines whatsoever.

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