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Pin-hole in oil pan - which product to patch it?

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John Doe 218/12/2021 12:25:09
84 forum posts
14 photos

Greetings, all.

I need to make a temporary repair on a car gearbox oil pan. It has rusted badly in one area and seems to have a pinhole which is allowing the automatic gearbox oil to seep out.

Ideally I would get it brazed, but for reasons I won't bore you with, I cannot remove the pan just yet, so I want to patch the leak for now.

Please can someone recommend an epoxy putty - or any other product - that would adhere to steel with oil on it, and survive a temperature of, say, 120°C for 6 months or so. I have searched this website for "epoxy", but am not sure which product would work with oil.

Actually, maybe an oil-based paint would do it ? I successfully painted an oily church bell-frame once.

Many thanks if you can help.


noel shelley18/12/2021 12:38:59
1347 forum posts
21 photos

Since only you can see it it's a difficult one ! Trying to seal anything containing oil thats leaking is not easy ! If it is a small area then I would try a mechanical method - a short self tapper and a dowty seal/ washer or plenty of PTFE. A can of brake/ clutch cleaner to degrease, then RTV gasket (silicon) for a bigger patch ! If you can drain first, better still. Good luck Noel.

Edited By noel shelley on 18/12/2021 12:39:44

Dave Halford18/12/2021 15:20:35
2050 forum posts
23 photos

If it's not too modern there should be a drain plug, otherwise the whole pan is the drain plug and things get much harder.

If you know where the hole is and you can get a set of ramps under the appropriate wheels to clear the pin hole of oil.

Sand the rust off as best you can and use resin core solder. It's possible to tin steel immediately under the iron tip with a 40w iron by rubbing it fairly hard. Small rust pits and the hole can be bridged with extra solder or a small piece of brass.

I would not insert any foreign body into the pan, if a screw punctures the filter or glue gets in there and sets you may need a box rebuild. Also brazing may distort it and give you a leak at the gasket.

Failing all that Petro patch (the fuel tank one) still exists.

Edited By Dave Halford on 18/12/2021 15:23:23

jimmy b18/12/2021 15:31:58
786 forum posts
42 photos

I'd go with JB Weld.

I've used this to fix a crashed motorcycle with a cracked casing, never leaked!



Mike Hurley18/12/2021 17:47:18
314 forum posts
87 photos

I don't think any kind of epoxy or sticky stuff will adhere to the metal properly unless you can totally get rid of any oil residue. You must get the surface thoroughly clean & dry before trying or it just won't be reliable. Like Jimmy B, I would suggest JB weld but only in conjunction with my previous comments.

Another possibility may be Ultra-Violet cured patches. Do an internet search for ' UV patches for metal ' ., but again the surface being repaired must be pristine. There is no magic fix t.o an oily surface that I'm aware of..


not done it yet18/12/2021 19:29:37
6812 forum posts
20 photos

IF there is sufficient clearance where the hole is, a blind pop rivet may suffice. I would prefer to fit a threaded insert as it can be displaced to one side of the hole (if very thin at that point) and a large sealing washer and fixing inserted with loctite. An easy job on an engine sump, but may not be appropriate for a pan repair on an automatic gearbox.

A blind pop rivet may well then allow JB Weld, or similar, to be applied over the rivet head.  Do not attempt to use a short open pop rivet as the pin could come adrift.

Edited By not done it yet on 18/12/2021 19:33:11

J Hancock18/12/2021 19:52:31
836 forum posts

I would be very surprised if it was just one pinhole.

If you 'mess ' with it I'm sure the truth will be revealed.

Only one safe way , replace or repair it properly.

old mart18/12/2021 20:41:55
3775 forum posts
233 photos

I agree with JH, if the pinhole is rust related, simply rubbing the surface to get it ready for a patch may start new leaks. If the oil can be drained to slow the spread after degreasing, I would have a thin steel patch ready coated with quick setting epoxy and press it on quickly on. The biggest patch that can be fitted the better.

Macolm18/12/2021 21:54:32
79 forum posts
19 photos

You will almost certainly find it impossible to get a bond with ordinary epoxy with any oil contamination. Petropatch now seems to be an epoxy putty - I suppose it might be formulated to work with existing oil contamination, but I doubt it. It was once akin to jointing compound, and a cloth patch. Also, there was a Bostik two component acrylic adhesive that would adhere to an oily surface, absorbing the oil. As an aside, there are epoxies that bond polythene ski sole material, so clever chemical action is possible.

Try search for oily surface adhesives. I found ThreeBond 1217M, but there should be others. Be prepared for a shock when you see some of the prices!

J Hancock18/12/2021 22:38:53
836 forum posts

And , if you get too many 'bits' inside the hole you are trying to seal it will finish off your auto box .

Do it right , or not at all.

Mick Bailey19/12/2021 12:22:34
30 forum posts

It may be possible to use very thin silicone or oil-tolerant synthetic rubber and one or more suitably-sized N52 neodymium magnets used as a magnetic clamp. Or apply a thin film of silicone sealer or other product to the magnet (even blue Hylomar), allow it to almost fully go off and then attach it to the area. It all comes down to where the leak is from.

Howard Lewis19/12/2021 18:43:33
6113 forum posts
14 photos

Sorry to be extremely despondent, but if it has one pinhole, it is likely that there are lots more waiting to appear.

If the plate is badly rusted eternally then there will be more pits waiting to perforate..

If the plate is reasonably good externally, it implies that there is, or has been, water within the transmission, again, with more embryo pinholes..

Many years ago, my father's Morris Minor petrol tank began to leak. The more we tried to solder up a hole, another one or more appeared. In the end we gave up and fitted a new tank!

You may be looking for an interim leak stop, until such time as the plate can be removed and replaced or fully patched. IFyou succeed with a short term stoppage, that plate needs to be sorted, one way of another, PDQ

It is going to be difficult to find anything that will adhere to a surface which is oily and ATF is low viscosity, so will spread easily. Degreasing with fluid still in, is going to be very difficult if not impossible.

If no replacement available, then a new repair plate needs to be welded /brazed over the outside of the plate, while it is off.


Robert Atkinson 219/12/2021 19:14:20
1209 forum posts
20 photos

If it is a reasonably flat surface and the leak is slow try this approach.
Cut a thin metal patch about 30-40mm in diameter. clean and degrease the area around the hole. Put a bead of 5 minute epoxy around the perimiter of the patch. Do a final degrease of the pan working inward. use acetone or similar fast drying solvent. Press the patch up to the pan and hold or tape in place while the epoxy sets.

Robert G8RPI.

john halfpenny19/12/2021 19:49:37
236 forum posts
24 photos

I have succesfully sealed a pin hole in a fuel tank at a spot weld. A drawing pin with epoxy under the head, after draining and de-greasing. I then epoxyed a second larger patch with a dished centre to house the pinhead. Still good after 20 years.

HOWARDT19/12/2021 21:45:27
909 forum posts
39 photos

A sealed pop rivet and maybe some high temperature flexible sealer under the outside head.

Mick Bailey20/12/2021 10:39:18
30 forum posts

Any disturbance of the pan could cause debris to circulate in the fluid. The slightest spec of anything can cause a valve sealing issue and mis-shifting or worse. Drilling or otherwise perforating the pan could result in a bigger problem than just a leak.

It would be a very unusual circumstance where just a single pinhole would form; usually the metal is so thin at that stage and corroded over a much wider area that it's not far off lacework.- I'm in agreement with Howard Lewis on this.

John Doe 203/01/2022 14:34:49
84 forum posts
14 photos

Thanks for all your suggestions.

I was looking for a temporary repair to stop the tiny leak until I can remove the pan to either replace it or weld/braze it, depending on its condition - a new pan is £250 for a bit of pressed steel !!!

Removing the pan is a bit involved and therefore not a "Saturday afternoon job". You cannot even access the oil drain plug, because there is a large reinforcing plate underneath the gearbox, and refilling the oil correctly is very involved too, so I wanted a product that would work with oil still in the pan. I don't have a four post lift, so will have to do the job under the usual axle stands on the driveway and want to wait for better weather and a time when the car can be taken out of service for a while.

The gearbox has a large internal filter for the oil, so minor debris would not be a problem, however blocking the pinhole with a screw or rivet will probably not work because the metal around it might be very thin now, owing to the rust on the outside, and as some have said, messing with the thin corroded pan wall may well open other pinholes - or worse !

I know there is underwater epoxy, but the only product that might work with oil is Threebond 1217M, but that is for making FIPG - formed in place gaskets, so it might not work stuck to just one surface.

I do like the idea of a small powerful magnet coated with sealant !

Oil based paint might also do the job, as I say I just want to temporarily stop or reduce the leak until I can sort it properly.


Edited By John Doe 2 on 03/01/2022 14:36:20

MikeK03/01/2022 15:27:13
226 forum posts
17 photos

JB Weld makes a "Tank Weld" product that would be suitable for oil pans as well. As mentioned, cleanliness is key. They also make a "Steel Stik" putty.

Nicholas Wheeler 103/01/2022 16:05:20
930 forum posts
87 photos

I've seen and used THIS STUFF for just that sort of repair.

clogs03/01/2022 16:37:00
626 forum posts
12 photos

I have a similar prob...the HYD oil tank is leaking on my forklift.....a large crack where the engine mopuntig braked is welded on to the tank side....

to repair it prop the engine needs to come out.....grrrrrrr....

I used a Polyurethene sealant and a metal patch's a bit like Silicone but much better....

cleaned everything off with spray brake cleaner.....

then a dollop, tech term, on the patch plate and slapped it on....

been there for 2 years now and not leaking........

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