rear oil seal

john.n · Post by **john.n** » Tue Apr 20, 2010 4:52 pm

i have split the dexta at the rear of the engine removed flywheel and replaced the oil seal round the crank. i have reasembled and run the tractor. found oil to still be leaking out the the back of the engine. i have used 30SAE oil. i have good oil pressure even when hot. but the engine suffers from crankcase compression due to worn rings/ liners. so will have to drop the sump out at some piont. i did wonder if the sump seal could be leaking causing the problem beacuse the leak is just as bad as before?

Dunggatherer · Post by **Dunggatherer** » Tue Apr 20, 2010 6:55 pm

Hello John,

Did you only replace the cordseal?

When i replaced some gaskets and seals i had ordered a complete kit for a Dexta engine.
It appeared later that i had received a kit for a Perkins engine.
Now that may seem correct,but there are different types,including a kit for a certain red and grey tractor.
This tractor has a different sump,so my sumpgasket lacked two "lips" which are to touch the rear (and front) crankshaft seal housing.
So my engine also kept leaking,until i rereplaced the gasket,this time with the correct type.

Hope this helps,good luck!

Rob.

john.n · Post by **john.n** » Tue Apr 20, 2010 7:11 pm

i have only replaced the rope seal and the gasket behind the seal holder. how easy is it to remove a sump without removing the whole engine? i have no engine hoist, split the tractor with nothing other than a trolly jack, a bottle jack and axle stands.

thanks

Dunggatherer · Post by **Dunggatherer** » Tue Apr 20, 2010 7:21 pm

Well if you are that creative with your tools,i think it can be done.
I believe it is possible to remove the sump while the engine is still attached to the clutch-housing.
So you could support the tractor there,and then ride the frontaxle away.
Then lower the sump.
But it has been a while,and i may have forgotten some details.
Maybe it's best to wait for some more replies.

O and what i once found was a worn crankshaft,from which that spiraling oilgroove was gone.
That groove sits precisely where you fitted the ropeseal.
Then the oil would not be directed back into the sump,so it would also keep leaking,no matter how many ropes you'd replace.
Cleaned up the crank,deepened the oilgroove and presto,fixed!

Aussie Frank · Post by **Aussie Frank** » Wed Apr 21, 2010 4:01 am

Hi John,

I think you will find that as long as you are pressurising the crank case with the worn rings and liners you will always have an oil leak. Rope oil seals can't stop oil under pressure. It is possible that your old oil seal was not faulty. Do the rings and liners and the oil leak will most likely go away.

Regards, Frank.

Post by **Brian** » Wed Apr 21, 2010 7:44 am

In another direction. Are you sure its not oil from the gearbox front seal?

pjjms · Post by **pjjms** » Wed Apr 21, 2010 8:48 am

I went through the exact same thing. I think the leak will now be down the front of the steel plate on the rear of the engine rather than from the hole in the bell housing. Replaced the crank seal and still had a leak on mine. Take the sump off and replace the gasket. The rear of the sump seals on the rear bearing cap using a square section cork strip, and I believe that was causing my leak. Do support the tractor as the sump is part of the structure (and heavy) and there are stories of blocks cracking when the sump is removed. Not sure if they are true stories but I didnt want to find out the hard way. I dont recall having to remove the front axle.

By the way, mine fumed like hell out of the engine breather at the time but this still fixed the leak. I assume the breather on the RH of your engine is not blocked?

john.n · Post by **john.n** » Wed Apr 21, 2010 4:54 pm

quite sure i was the engine seal because some fool had put a rawl plug in the drain hole in the engine block just infront of the adapter plate. so there was about 1Lt of oil trapped between the engine and adaptor plate, this was then overflowing out into the clutch housing. round the gearbox input shaft seamed dry. which seal is it that normally fails? its a live drive by the way. oil now only leaks out the drain hole at back of the engine.
the braether pipe is not fitted at the moment because i forgot to paint it, the pipe out the rocker cover is not blocked. ant there is plenty of smoke from it.
is it possible to replace piston rings and hone the liners through the sump? my engine has good oil pressure even when hot. (guessed this because if the engine is cranked when hot with the stop pulled the light will not light back up for 4 secs after everything has stopped) so is it worth replacing the bearing shells? dont really want to remove the crank.

many thanks

pjjms · Post by **pjjms** » Thu Apr 22, 2010 9:57 am

If it is leaking down the front of the adaptor plate then the sump needs to be resealed.

I believe the rods will come out through the cylinders so assuming theres no big lip on the bore you will not have to remove the crank.

Post by **Brian** » Thu Apr 22, 2010 10:35 am

John.

The engine was fitted with "Cord" rings when new. These rings are great for oil use control and wear well but when they wear out the bores are usually badly worn as well. I would suspect, to cure your breathing problem you will need to replace liners as well as pistons and rings.

At the same time you should have the crank checked and re-ground if required.

There really is no halfway house when the engine gets worn. A previous owner may have used ether and what you are seeing is the result of broken pistons and rings.

john.n · Post by **john.n** » Thu Apr 22, 2010 5:25 pm

what sort of price am i looking at to have new liners pressed into the block? and also how much would a crank regrind cost?

when i changed the oil i had the round pump screen out from the sump, looking up, i could see no big scratches on the side walls of the liners. everything seems to work fine except the white-ish smoke coming out the breather pipe. then engine started up quite easy yesterday with a newly charged battery. anythoughts on where best to spend my money?

Post by **Brian** » Thu Apr 22, 2010 6:42 pm

You will not see anything from the filter hole, the caps have to come off and the crank will have to be measured.

You need to put the price question to a local engineering shop, they will give you a far better idea than we can.

When I did Henrietta a few years ago, I did not need liners, just new rings but I had the crank re-ground, all new bearings and thrusts, new clutch plate and all the gaskets came to £350.00.

Agrline does new cranks for the Dexta range, you might try their web site to get an idea.

john.n · Post by **john.n** » Thu Apr 22, 2010 8:44 pm

many thanks for the advice.
will either do any harm to the valves? it looks like it may have had the head overhalled in the not so distant past.

pjjms · Post by **pjjms** » Fri Apr 23, 2010 6:31 am

John,
We all like to keep our tractors in good condition, however Money does not grow on trees.

I don't think the engine fuming will do any damage. There is the option to just keep using it like it is. If it was me doing that I would remove the sump to fix the oil leak, but while its off take a few big end and main bearings caps off to have a look at the condition of the bearings and crank. If they are not in too bad a condition I don't think you will do much harm putting it back together and using it (assuming its not if full time hard work).

The way I see it the risk is wearing the crank bearings too far and damaging the crank beyond regrinding. You won't do much harm to the bores, and as you note they are not scored now so you probibly won't have any broken rings to damage them further.

Of course if you wish to spend the money reconditioning the engine would be nice.