stopping sump pan drips

[JonE]

I spent so long fashioning a silicon gasket (which does a great job) that I didn't consider the travel of oil down through the sump bolt thread. The sump has emptied itself of 1/2 pint of new oil in a week.. and appears to be coming out of two of the bolt locations judging from the drip. This is a 3 bearing crankcase.

Is there a rule for which ones (have the potential to) leak and which ones have blind locations (and thus can't)?

And what is the best sealant for these - a bit of copper loctite sealant on the bolt end as it's put in? Or squeeze some into the hole first?

[Steve Jones]

In theory, it's pretty easy to list which of the holes are blind and can't leak and which are not and can. However, reality is that a lot of crankcases have blind holes that are no longer blind because they've been opened up by misuse over the years and the safest way is to treat all the holes the same way although those at the rear of the crankcase are often the biggest problem because they're not blind and have the largest head of oil around them.

Plan 1 is to wind a couple of turns of PTFE tape around the bolt thread. Make sure you do this in such a direction that doesn't cause it to 'unwind' when fitted. With the normal oval washers and a spring washer this often works. Using any form of silicone sealer on the thread doesn't. Plan 2 is to use the PTFE tape but replace the oval washers with Dowty seals (Bonded Washers). Plan 3 if you still have a drip is to replace the bolt with a threaded stud. Used with a Dowty Washer this should be a belt and braces option as given that with the unthreaded section in the middle of the stud, their isn't a continuous thread for the oil to run down.

I've used all options over the years and, usually, succeed in the end. My new hillclimb engine that's only had oil in it for a week has the sump fitted as Plan 1 but I note that one bolt is showing just a touch of oil to its head so will need to be re-visited in due course.

Steve

[Chris KC]

Thanks for that timely reminder, mine leaked like a sieve last time. I'm just about to make some thread inserts and shall endeavour not to drill them quite through!

Studs can make it a nightmare removing the sump on some cars by the way.

[JonE]

Phew. Thanks for those. I'm glad it's not just me! PTFE it is for first round.
I'm now off to search for that bargain barrel of 20/50 that someone posted a while back (that at the time I thought, that's rather a lot of oil... but...)

[Bob Culver]

Oil leaking down threads is common in many older cars in many places and is not realised by very many. With Sevens, because there is no filter afer the sump, great care s necessary not to get bits of cork, thread tape etc into the sump .Fibre washers the usual cure for leaky threads. Not acceptable on cars generally as owners expect to never check bolts but fine on a Seven

[John Mason]

I found a quick and easy solution to this problem was to undo the offending bolts until they were almost out the threads, then wrap PTFE tape around the bolt between the sump itself and the oval washer (it doesn’t matter if the tape gets twisted whilst doing this). Then retighten the bolt. This distorts the tape making a tight sealing washer between sump and oval washer. What oil seeps down the threads is sealed not engine side of the sump but on the outside between sump and washer.
Not an engineers way but a non engineer thinking outside the box.

John Mason

[JonE]

great. will try that first and not drain the rest out!