990a crankcase pressure

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bel
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990a crankcase pressure

Post by bel » Sat Feb 17, 2018 6:01 pm

Three days ago started tractor noticed fan wasn’t turning killed it bottom pulley had come off crankshaft. Put it back on with new nut put belt back on was using tractor to mow. Heard loud pop blew oil fill cap off. Think it’s unrelated but wanted some other opinions. Sounds like busted piston or rings to me

joeproctor
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Re: 990a crankcase pressure

Post by joeproctor » Sat Feb 17, 2018 6:08 pm

have you noticed the tractor breathing before this incident?does it still start and run ok?

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db2d
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Re: 990a crankcase pressure

Post by db2d » Sat Feb 17, 2018 7:02 pm

Be certain that the engine breather tube and filter are clear. The filter and tube are situated on the front upper part of the valve rocker cover. The filter can be discarded.

bel
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Re: 990a crankcase pressure

Post by bel » Sun Feb 18, 2018 12:12 am

It does start and run a lot harder to start and smokes more than normal and running rough not knocking or anything constant pressure coming out of top of valve cover and you can’t put oil fill cap back on with it running major compression coming into crank case. Hole in piston or blown head gasket ? Thoughts?

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rid54
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Re: 990a crankcase pressure

Post by rid54 » Sun Feb 18, 2018 12:10 pm

A hole in a piston would probably be noticeable by uneven cranking (no compression in the affected cylinder). If possible, do a compression test or just listen to the "rhytm" when cranking. Seems likely you'll have to get the head off of the engine anyway. Problem might be due to a temporary overheating as the pulley came off the crankshaft (no coolant circulation).

Gard
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Re: 990a crankcase pressure

Post by Gard » Sun Feb 18, 2018 10:46 pm

My 990 has been breathing or pressurizing the crankcase for years. My guess is it needs rings but it continues to work well for what I use it for. Seems like it runs better after being worked hard for awhile. Probably used on average only 5 hrs a week. Biggest thing I found is to leave the oil filler cap off or it will pressurize and leak oil onto the clutch and everywhere else. I found a piece of radiator hose that fits over the oil filler neck and bends down twords the ground. I plan on doing a rebuild one of these days. I hope I am not doing any more damage by continuing to use it.

bel
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Re: 990a crankcase pressure

Post by bel » Mon Feb 19, 2018 12:14 am

Ok pulled head off one piston had slight mark where valve hit you can’t even feel mark on top of piston. My question is timing off? Even if it is why crankcase pressure head gasket was fine not blowed. Should of done compression check but didn’t I was already removing head. Now wondering if rings are ok

bel
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Re: 990a crankcase pressure

Post by bel » Mon Feb 19, 2018 12:18 am

Hard
I had a pickup that way blew oil out dipstick got tired of buying oil so put tubing on it and had it going back into oil jug everyday poured it back in lol. Didn’t last long though few months

bel
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Re: 990a crankcase pressure

Post by bel » Mon Feb 19, 2018 12:19 am

Sorry gard spell ck

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rid54
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Re: 990a crankcase pressure

Post by rid54 » Mon Feb 19, 2018 9:01 am

+1 on piston rings. What kind of camshaft drive has this engine? Hard to see the gear type drive lose timing, actually; chains may jump a cog though and if so the underlying cause must be fixed.

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ollek
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Re: 990a crankcase pressure

Post by ollek » Mon Feb 19, 2018 9:47 am

All David Brown engines have a gear train for driving camshaft, injection pump and possible power steering pump. Chain drives are used in cars, but very seldom (if ever) in diesel engines for industrial or agricultural use.

KevinC
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Re: 990a crankcase pressure

Post by KevinC » Mon Feb 19, 2018 2:41 pm

If the valve has touched the piston enough to mark it best check that the valve stem is not bent. Probably not but you don't want to put it back together and then find you have another problem

bel
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Re: 990a crankcase pressure

Post by bel » Wed Feb 21, 2018 2:36 am

if nothing wrong with head gasket only thing it could be is rings on one cylinder right? Breather on valve cover was clear and still haven't found oil fill cap in field someplace no where around tractor. lots of crankcase pressure.

KevinC
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Re: 990a crankcase pressure

Post by KevinC » Wed Feb 21, 2018 7:24 am

A shame you didn't do a compression test before you took the head off. I agree it must be rings on one cylinder and I think you are looking for breakage not wear if this problem started suddenly. I am afraid you are going to have to pull the pistons to find out. I had this on a land rover v8 once, it was the last one I took out! Start with the piston with the mark on it just in case the two things are connected although I can't think why they could be. Good luck

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rid54
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Re: 990a crankcase pressure

Post by rid54 » Wed Feb 21, 2018 8:54 am

I think all the pistons should be taken out and checked. If the engine has overheated (no fan/water pump for a while), rings may be jammed or damaged on more than one piston.

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