Sump oil leak

[daverubberduck]

I need help - I started up the engine for the first time since I bought my +2 as a part done restoration. It leaked oil from the sump fairly badly so I decided to replace the sump gasket. I set about loosening the sump bolts and found the one next to the oil filter to be already quite loose, and that was clearly where the leak was. Also there was black sealant in that area suggesting someone tried to fix the leak before. So I tried tightening the bolt just to see if it would, and of course it didn't. I can't find a thread (no pun intended) on this forum that exactly matches my problem but I'm guessing it must be fairly common. So what is the best way to go about fixing this?
Dave

[john.p.clegg]

Dave

So I tried tightening the bolt just to see if it would, and of course it didn't.

Would the bolt not tighten

or

It didn't cure the leak

John

[rgh0]

If its the bolt into the alloy front casing the the threads are commonly stipped by people over tightening them.

You need to remove the sump and helicoil any stripped threads and then refit with new gaskets. Use a good gasket adhesive (e.g. loctite No3 aviation gasket sealer, not silcone) to stick the gaskets in place so they dont squeeze out. Only use a small amount of silicone in the corners where the flat gasket meets the round sections over the crank. Hex socket bolts and a ball headed allen key makes refitting the bolts easier - especially the two rear ones. Tighten up the sump evenly and avoid over tightening. Retighten a couple of times after you have run the car a few miles

cheers
Rohan.

[daverubberduck]

Sorry John, I meant did not tighten.

Many thanks Rohan for excellent reply. You are right, the bolt in question is into the alloy front cover. I have never done the helicoil thing before but I guess it's time to bite the bullet. I will post on here how I get on.
Dave

[EPA]

Dave
When I first got my car the sump leaked quite a lot because of the threads being stripped and I used the helicoils for the first time. I found it quite simple to do and it worked very well.
The one thing I would mention though is that a few of the sump bolts fastened into blind holes (Ie the bolt doesn't come through to the other side). I realised that these when tightened did not actually tighten the sump because they bottomed out before doing so. In the history that came with the car someone had replaced the existing bolts with longer ones (presumably to overcome stripped threads). I can't recall how many of these there are but something to look for.

Best of luck
Ed

[gus]

One thing you might want to do some tin work on the sump. The area around the holes becomes dimpled from over tightening. Lightly hammering the dimples and dressing with a file until it will sit flat on a flat surface. Check that the flange sits flat also and it may need to be bent back true.

When installing in the car I find using enough sealant to adhere the gasket to the block then offering the pan up to the block works best. Perhaps in a perfect world no sealant works, but in the car I think this is best.

[daverubberduck]

Many thanks Ed and Gus for the tips, very helpful. I have removed a couple of the bolts and they look to be M6 with 12mm length of thread and thread size about 1.3mm. Does this sound about right? Obviously I need to get the right helicoil kit. Ed - which size did you use?

Interestingly, actually that should read depressingly, there is quite a pool of oil that has collected on my garage floor near the back of the car since I've had the front jacked up. It seems to have come out of the central tunnel of the chassis. I'm hoping that this is engine oil that has just blown back but I am sceptical about that because the car has hardly been driven since the chassis was changed, just a quick test drive down the street. I will continue with fixing the sump and then we will see I guess.
Dave

[rgh0]

The sump bolts should be UNC. The oil in the backbone typically comes from the gearbox rear seal.

cheers
Rohan

[daverubberduck]

Thanks Rohan, so 1/4" UNC 1/2" long 20tpi. Are they all the same? I read somewhere that 2 might be different, perhaps the 2 into the front cover?

So engine and box out to fix the other leak, that's bad news.
Dave

[RichardHawkins]

Rohan,

You advise against silicon rubber gasket dressing, why is that?

I had intended to use Loctite 5900 or 5910 both are silicone rubber. I have tried several different gasket dressings, and these two seemed to give the best adhesion. All my trials had been without the engine in use. I am about to complete the assembly of the engine, and want to do the best I can.

Richard Hawkins

[EPA]

Dave
The helicoils I used were 1/4 unc.
The oil on the floor is probably coming out of the rear gearbox seal,you can tell by the type of oil.This brings back memories as mine did exactly the same.
Ed

[daverubberduck]

Thanks Ed.

It must be gearbox oil, and there is way too much considering the car has had so little running since the chassis was changed. Forgive my ignorance but how do I tell for sure that it's gearbox oil? Is gearbox oil thinner?
Dave

[EPA]

Dave
It's thicker but more obviously it's clean,engine oil is blackened by carbon deposits.
If you look at the rear of the gear box where the prop shaft connects it should be obvious if it's leaking.If the seal needs replacing also order a new propshaft yoke as the seal tends to wear a groove in the shaft and the new seal won't cure the fault unless you also replace the yoke, the yoke is the short shaft that enters the gearbox and also connects to the propshaft front universal joint..
The gearbox seal can be replaced without removing the box from the car(although I think this depends on which chassis you have,mine is Spyder), but it's a real pig to do because of the limited access. I think that I would try making some kind of puller if I was going to do it again.

Ed

[rgh0]

Thanks Rohan, so 1/4" UNC 1/2" long 20tpi. Are they all the same? I read somewhere that 2 might be different, perhaps the 2 into the front cover?

So engine and box out to fix the other leak, that's bad news.
Dave

The two at the rear in the 4 bolt crank sumps were longer. In the 6 bolt crank sump they are all the same. The rear seal in the gear box is not an easy fix. It often leaks due to wear in the bronze bush the prop shaft end runs in just behind the seal so you really need to replace both.

Even one in good condition will normally leak a little when you jack up the front of the car so I would not normally try to fix it unless you are already pulling the engine for another reason.

cheers
Rohan

[rgh0]

Rohan,

You advise against silicon rubber gasket dressing, why is that?

I had intended to use Loctite 5900 or 5910 both are silicone rubber. I have tried several different gasket dressings, and these two seemed to give the best adhesion. All my trials had been without the engine in use. I am about to complete the assembly of the engine, and want to do the best I can.

Richard Hawkins

The problem is that most people over use silicone and over tighten the components before the silicone sets. This results in silicone getting into oil passages and causing problems or if used with a gasket the gasket squeezing out of the join. Even if you know what your doing it is not easy to get a cork gasket to adhere properly without excessive silicone squeezing out.

Many modern engines and gear boxes are assembled using silicone without gaskets but the type of silicone, the machining of the faces and the silicone is computer applied and the assembly methods are all carefully engineered. Squeezing some silicone out of a tube onto a cork gasket between an old pressed steel sump and cast iron block is not quite the same thing

I thus prefer to use a non silicone adhesive / sealant for sticking cork gaskets to components

cheers
Rohan..