My xj6 series 3 4.2L jag has oil leaking between the bell housing and the rear of the engine. I’m guessing it the rear mains seal. This leak has been there a long time but might be getting worse. Could it be something else?
If it is the rear mains seal, is it possible to replace it without removing the motor? If the motor comes out is it a complete disassemble of the engine to get to the seal?
Cheers,
Andrew
Check the oil banjos feeding the cams. Even if the faces are oil-tight the solder can crack if they are twisted during tightening. Check also the rubber half-moons for shrinkage leaks and cam covers for cracking or gasket slippage. Basically, clean the area bone dry with rags, tissues and carb cleaner then see where the leak comes from. You may need no more than gaskets and half moons, with new or flattened/annealed copper cam cover washers.
Once you get the top end bone dry, or if it already is, double check if it’s engine oil or transmission fluid. If it’s engine oil it might be the sump or filter gasket or a front seal leak migrating along the block, or the seal between the sump and the main seal housing.
Yes, it probably is the main crank seal but it’s worth checking everything else first because on an XJ or any subframe model it’s engine out or subframe drop to get access. It’s the same for the other sump-related gaskets.
If it is the crank seal you have to separate the transmission to get behind the flywheel/flex plate and remove the seal holder.
Or you could try running a quart low on oil in case you’re over-filling slightly, or just park in the street when you visit friends…
Andrew!
These cars seem to have a weak spot for leaking at the rear
of the oil pan.
Just drop the pan and put some new seals in, not too much work.
Try to get the front seal and the rear seal at the same time.
I did all that on my 1978 XJ6 ser.2.
Rockauto.com should have it.
How many miles on the engine?
Walter
Thanks Peter. Is the rear main seal a rope seal? If so, are there any additives that can help or is that just wishful thinking. There always seem to be drawbacks with using these miracle products.
Hi Walter,
The pan seal is fine. It looks like a rear mains seal around the crank that is leaking. Engine has been around the clock a couple of times.
I dunno about the 4.2, but on the V12 a rear main oil seal leak is usually a sign of a PCV system not working properly. Fix it and the leak goes away. On an engine that’s been around the clock a couple of times, it might be worth installing a second PCV system, presuming the blowby is simply overwhelming the first one.
Wishful thinking…
It leaks when parked and it’s a rope seal. How much drips out, and how much experience do you have?
The miracle products act by altering the nitrile seals to swell them a little and close up mild gaps. However, the gap is caused by wear of the sharp seal edge and this cannot be restored. The whole ‘point’ of the seal lip having a fine edge is to raise the seal pressure without adding too much friction, by concentrating the fairly light garter spring pressure into a tiny area. So if the edge on a brand new seal is, say, 0.25 mm and a worn rounded edge is 1 mm wide, the same spring force would grip the shaft by a quarter of the surface pressure. In practice, since the spring is stretched less because of the reduced diameter, the force will be even lower at the seal edge.That latter loss of pressure is probably what the seal additives restore by swelling the rubber, but it’s only temporary at best.
Since the rope seal isn’t made of rubber (although some of the white ones do have a rubber bead inside them) it doesn’t respond to solvent plasticisers in the additives.
However, now that I read the poor thing has likely gone faithfully twice round the clock, I think you’ve had your money’s worth. You should either leave the poor girl alone and stop picking on her, or treat her to a total revamp. Most of us would dribble if we’d gone twice round the clock!
When the engine oil level is above half of the XXXX section on the dipstick, my 71 4.2 engine leaves more oil drops on the garage floor. The worst time was just after a service. The workshop filled it up to almost 1cm above the full line. I found a lot of oil coming out from the dipstick tube and ended up on floor. I will order PCV gaskets from JagDaim and do a cleaning in the weekend and see if condition improves.
Check the breather at the front of the cylinder head and make sure the screen is not clogged. If the breather is not working properly then crankcase pressure will rise and push oil out various locations.
Paul
Thanks Paul, is there a pcv valve as well as this mesh filter breather?
I am not familiar with the Series I cars and emissions equipment varied depending on the market. It would be best for someone from Australia knowledgeable in the Series I answer that question. All the XK engines had that breather assembly and I have seen that mesh screen pretty clogged up in some of my parts cars.
Paul
Thanks Paul. My car is S3. It has the mesh filter. Just found out the s3 doesn’t have a pcv valve.
Thanks for the description of the additive. Yes, it might need a rebuild.
Why don’t you try adding one? Certainly cheaper than a rebuild.
Turned out that the leak from the rear of the engine is not a bad rear mains leak. Was just bad diagnosis from a mechanic trying to drum up work, who couldn’t be bothered looking at what the leak actual was. When I investigated I found a transmission cooler line with a small hole in it, squirting transmission fluid onto the block. They just assumed it was rear mains leak. Hoping they’d get a rebuild job out of it. Outrageous!
Anyway, fixed the leaking line, cleaned up the engine and virtually no engine oil leaking.
Great result…
YIPPY!!!
I do like the idea of adding PVC. Positive Crankcase Ventilation. The existing passive system is marginal at best. Not much better, if at all, than the old “road draft” systems.
There are benefits from a negative PSI in the crank case.
My experienced Jeep has a weeping rear seal. .No plans to fix, either by chemistry or mechanics.
My son has an ancient fork lift powered by a 51 Plymouth engine. Well worn Main seal leak has messed with the clutch. Fix: Take it apart. clean out the flywheel area. Wash the disc many times in various solutions, including gas.
Improve the dut cover drain, ie, big hole. Should work if no puddle takes place and the ring gear teeth splatter oil on to the disc…
OH, the fork lift was once WWII vintage weapons carrier!!!
