Oil leak after a run

[SimonBrown]

My E Type (Series 2 OTS) is normally pretty dry underneath.
However, after a 50 mile run on Monday, including a 30 mile motorway stretch and after parking on my drive for about 10 mins there was a small pool of oil underneath the rear of the engine, followed by a few more drops on the garage floor overnight.
The back of the sump was dripping with oil and also the exhaust was covered. I have wiped it all clean and after a 10 mile run last night not a drop has leaked.

Any ideas anyone?

Thanks and regards

Simon

[mgcjag]

Hi Simon...have you recently changed/toped up the oil or had the car serviced....possible overfill?.....Steve

[abowie]

How long since your last run. I find if I leave a car for a while (months) and the rear seal dries out it will leak until it gets wet again. Then it seems to be OK.

[SimonBrown]

The car is used at least weekly for relatively short runs, 5 -20 miles each way, but this is the first time in a while it has been at 70 mph constantly for 30 miles. Oil was changed late last year, approx. 700 miles ago and is half way between min/max on dipstick. The engine was rebuilt 3 years/1500 miles ago
I am wondering if crankcase pressure is building on a longish motorway run, although I have checked the breather and all seems clear?
Regards
Simon

[mgcjag]

Hi Simon.....have a good look at the cam feed pipes at the rear of the head...oil could be running down from here..check for possible cracks in the pipes?

[SimonBrown]

Hi Steve,
These appear dry
The wetness would appear to be at broadly sump gasket level, nothing above.
It has leaked substantially as the bell housing was covered in oil, the exhaust flexi joints and front of the silencers. There were also drips apparent on the three
rearmost sump bolts on the RH side of the engine. Left side sump bolts all dry.

Thank you

Simon

[mgcjag]

Hi Simon.....well your options are rear seal or sump gasket..you could just check the sump bolts......like the saying goes ..if your Jag aint leaking it will soon ...most of us have it

[SimonBrown]

Hi Steve,
Yes, it is looking that way
I don't understand why it doesn't leak at all after a 15-20 mile "A" road run with varying speeds, but a 30 mile 70mph motorway run causes it to leak so badly.
Regards
Simon

[mgcjag]

Hi Simon...i doubt very much that on short run that everything has fully warmed up and the oil thinned a bit...longer run higher speed more revs higher oil pressure all make small leaks a bit worse

[chrisfell]

Check the pipe from the oil filter head back into the sump. This can perish. (Ask me how I know.) Under normal sedate driving the oil bypass valve in the oil filter head isn’t opened, but on the motorway prolonged running at high-ish rpm can see the oil bypass valve opening and excess oil being returned directly to the sump. If the bypass pipe is perished, some of that oil will find its way out of the engine.

If it is the bypass pipe, please note it has different diameters at each end, a length of ordinary oil resistant pipe will not do. Others will chime is with availability.

[AshM]

Angus has the best one. Different diameter for each end and supplied slightly over-length so you cut it to fit perfectly.

[SimonBrown]

Have checked the return pipe and it is completely dry.
It does appear to leak only after a run at consistently high engine speed (2500-3000rpm) and then leak quite badly.
Even after 15-20 miles on normal roads it is completely dry
Could it be crankcase pressure building on a longish high speed run forcing oil out of the rear main/sump?
Thank you for the ideas
Simon

[mgcjag]

Hi Simon...you did say you checked the breather...but worth re checking.....have you removed the breather plate on the front of the head....also where does the outlet go.....into the air plenham....lookinside to ensure its open

[SimonBrown]

Hi Steve,
I will try both of those as I do think it is something related to consistent high speed for a while.
I have just looked underneath following a 10 mile drive last night and not a single drop on the floor. There is not even a build up to a drip on the sump. There is the start of a drip on the bottom of the oil filter but I can’t see that would naturally leak the quantity it did on Monday
Appreciate your help
Simon

[malcolm]

Probably not a cause, but I did have a recent disaster where the gasket between the oil filter head and the block went. Bolts were loose, causing a leak, until at high speed the gasket blew and my oil disappeared. Thing is, it's quite hard finding the source of a leak. It flies around and seems to come from places it doesn't! So maybe check the 4 bolts just to be sure.

[Series1 Stu]

It's probably worth repeating the 30 mile 70mph run to see if it leaks again. It could be that, as Andrew suggested, now that the rear seal is wet it will be doing it's job once again.

Regards