MF TEA low compression

[MikeyMonster]

Hello
Ive a Massey Ferguson TEA28 (i think the 28 is the nz version of the more common 24 but im not sure). Anyhow it has low compression in cylinder 2.
90,50,90,90. I thought it might be a bad valve but it doesnt appear to be. Im wondering if anyone has any tips on working out if its the headgasket or the piston/rings?
Also can you replace the pistons on these by removing the oil pan and dropping the piston out from below?
Its a petrol by the way.
Ive never worked on a tractors or cars engine internally before although i can rebuild a two stroke outboard motor as easy as pie.
I appreciate any response
Mike

 

[Baby Grand]

It's been a while since I had any bad head gaskets, but I remember different symptoms, depending on where the gasket failed:
Blowing coolant into the oil, in which case the oil becomes milky looking.
Sucking coolant into the combustion chamber, in which case the exhaust is very thick, white and smelled of antifreeze.
Blowing air into the coolant, in which case the coolant tank would periodically over-fill and there were air bubbles in the coolant.
For bad rings, I'd expect to see dark, oily smoke and increased oil consumption.

 

[banjodunn]

G'day prob a bad valve so whip the head off it pistons will not come out the bottom, full engine rebuild kits are avail for about $500 so go for the full kit and get the head done and you should have it done in a day.
Good luck


Jon

 

[MikeyMonster]

Thanks for those replies.
I brought her back to the house, she started up fine out in the field and ran on the level fine but when i tried to go up a hill i got a backfire followed by a bigger one which kind of could of given someone shell shock. It stopped the engine and sent fumes through the oil breather and out the air filter container. Also on restart (which took a while) I noticed some fumes were constantly pouring out the rocket gasket. I guess thats from the gasket being worn there but whether there should be exhaust coming out of their normally i just dont know.

Heres a video of her running. Please excuse the small lawnmower tank that i used to get me home. I couldnt get the backfire to repeat, perhaps for some reason it requires a big load to do that. I rechecked compression and it was still 90 50 90 90.

 

[MikeyMonster]

Ive removed the rocker cover, there was two little bits of oily milky substance on the inside cover, im thinking that could just be from condensation over the years. Theres no other signs of water ingress and no sign of fluid loss from the radiator although i cant get an accurate reading on that.
Ive checked the rusted bolts on the out side of the head and on the exhaust manifold and they arent seized so i dont expect trouble there.

The rocker area is quite dirty, im tempted to run some diesel though the oil for a few minutes to clean her up a bit.
Looks like i will at least need to raise the head and check out the valves on that cylinder and then consider lifting up piston 2 for inspection.
Before i can lift the head I can see a few head bolts under the rocker cam that will need to be undone and also the connections from the push rods that will need disconnecting. Ive never dealt with valves before, they look like they must be under decent tension so are thus dangerous and need appropriate care.
I dont have a spring compressor and i live rural so visiting a parts place isnt very easy. Can i undo the push rods connection to the rocker arms by moving the engine to where the spring is extended to its max (not compressed to its max) and its seating the valve back in its seat and undoing the pushrod from the rocker arms then? Doing that to all rockerarms and then undoing the bolts which hold down the cam? Do i need to take note of adjustments then?

The worn rocket cover gasket can be seen as well in the photo

 

[MikeyMonster]

Ok i am pretty confident ive just shown that ive never rebuilt a four stroke before. To remove the rocket shaft it appears that all i need to do is remove the three or so bolts holding it down? As the rocker arms are actually not attached to the push rods and the rocker arms are also not attached on their other end to the top of the valve by the spring as the gap between the valve stem and rocker arm is what is measured as the valve gap.
So i hope to get this off during the weekend and report back on whether i can see the probable cause for the low compression.
Any further tips that could help would be appreciated.
It doesnt seem like getting this apart will be a hard task, so far

 

[Baby Grand]

Worn valve guide might be another low compression reason?
You'll know more when you get the head off.
Make sure you have the correct torque & sequence to put it back together before you take it off.

 

[Agvg]

You lift it right up, there are workshop manuals for download on the net, get one of those

 

[MikeyMonster]

Worn valve guide might be another low compression reason?
.

Im hoping its something to do with the valves, i really dont want to have to deal with a dirty oil pan etc if it is the rings. I hadnt known a valve guide could wear so thanks for pointing that out. A parts dept guy did actually give me a price on one of those guides and i had wondered why. Prices for things are relatively cheap, top gasket set $48NZ
($30US) and a valve is only $14. I plan to lift her up monday or tuesday depending on the weather.

 

[MikeyMonster]

You lift it right up, there are workshop manuals for download on the net, get one of those

Any chance of posting a link please. I have found that the head bolts are 100Nm and the rocker shaft is 60Nm. I was thinking that the head gasket tightening sequence would be inner to outer done in two stages.
I havent removed the pushrods but i assume i just pull them out before i lift the head.
My current job is detaching the thermost area from the front top of the head, after that il be lifting her.