Longtime lurker, I,m looking for valve clearance specs for my tractor. The engine is a ZN390T by ChangChai, Ltd. I am getting serious pressure buildup in the valve cover. The blowby hose and bowl seem to be clear. I'm hoping a valve adjustment might help, any thoughts?
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Taskmaster 432E valve clearance
- Thread starter ORPharmer
- Start date
- Views: 5552
Bob Rooks
Elite Member
My thoughts are piston rings and valve guides. How many hours on the engine?
Ranch_Hand_Supp
Advertiser
ORPharmer said:Longtime lurker, I,m looking for valve clearance specs for my tractor. The engine is a ZN390T by ChangChai, Ltd. I am getting serious pressure buildup in the valve cover. The blowby hose and bowl seem to be clear. I'm hoping a valve adjustment might help, any thoughts?
Sorry, don't know the valve spec's .
When you say you are getting serious pressure build up in the valve cover .... what do you mean?
Is it blowing out the valve cover gasket?, blowing the breather hose off??
Does the engine still run smooth ?? having to add engine oil??
Ronald
Ranch Hand Supply
Here is a bit more info. The engine sounds fine. I took the valve cover off and started the engine. The back cylinder shoots oil up about 12 inches out of the valve stems. The others just an inch or so. Next, I put it back together and removed the hoses from the breather, one still attached to the valve cover and the other to the crankcase. Oil still gushed out of the bottom hose. I stuck it in the oil filler hole on the valve cover, stuck a rag over it and it still sprayed all over. When all hoses are in their proper places, pressure really builds. I loosened the oil filler cap and it popped off! When I leave it on but loose, oil just wants to spray all over. I reduced the oil pressure via the screw down by the filter, no change. I'm obviously not a mechanic, so this is about as far as I can take it. Thanks for the help so far. I wouldn't mind getting the engine manual (I need one anyway) and playing with it, but this is the wrong time of year for that.
Bob Rooks
Elite Member
So you're talking about oil pressure, not crankcase pressure (blow-by)?
Bob, To tell you the truth, I'm not sure. As I said I'm not a mechanic. I did lower the oil pressure with no change in the pressure that builds up under the valve cover. Perhaps someone can educate me on the purpose of the 'blowby" system. There is a hose out of the top of the valve cover that feeds to a bowl filled with coarse steel wool material. It then proceeds down to a fitting in the side of the crankcase. When I first noticed the problem, it had blown the hose off between the bowl and the valvle cover and was squirting oil out of the bowl all over everything. When it first happened, there was so much oil, I couldn't tell exactly what had happened. It was only after these "experiments" that I am able to piece together the problem as stated above. As I said before, it still sounds and runs fine. I haven't even lost enough oil yet to have to top it off. I just can't run it without spraying oil.
Bob Rooks
Elite Member
"Blow-by" is a symptom caused by badly worn valve guides, piston rings and/or cylinder liners, allowing excessive combustion gasses to leak by, and in some cases overwhelms the Positive Crankcase Ventilation (PCV) system.
I am not that familiar with your brand of engine, but it sounds to me like the PCV system is not allowing the condensed oil to return to the sump. Sure would be nice to see a picture of the hose setup.
I am not that familiar with your brand of engine, but it sounds to me like the PCV system is not allowing the condensed oil to return to the sump. Sure would be nice to see a picture of the hose setup.
I finally got tired of digging by hand this afternoon and took matters into my own hands. To make a long story short (although it's a pretty good story) it appears that hydraulic oil is somehow entering the crankcase, causing the oil level to get too high causing the excess oil to exit via the blowby system. The only place I can figure the two can mix is through the shaft that runs the hydraulic pumps. If this is true there must be a seal on the shaft out of the engine and also on the pumps. Anyone have a problem with any of these seals? Thanks for all of the help so far.
Bob Rooks
Elite Member
There is no such thing as a "blow-by system".
Many people have experienced those symptoms of hydraulic oil migrating to engine or transmission sumps. It usually means a blocked or severly restricted hydraulic circuit allowing the pump to "deadhead". This is not indicative of Chinese tractors either.
You will have to change your engine oil and filter, rebuild your hydraulic pump, and find out where the problem lies. I would start with the relief valve.
Many people have experienced those symptoms of hydraulic oil migrating to engine or transmission sumps. It usually means a blocked or severly restricted hydraulic circuit allowing the pump to "deadhead". This is not indicative of Chinese tractors either.
You will have to change your engine oil and filter, rebuild your hydraulic pump, and find out where the problem lies. I would start with the relief valve.
