TheSamba.com :: View topic - found the leak! small crack around the oil pres switch (pic)

Fri Mar 19, 2010 7:36 pm

Well guys,I've found the oil leak that was pooling on the tin behind the pulley (engine is 'B' series 1600 SP). Its this small crack above the thread that holds the oil pressure switch,check out the pic...

so how do you think I should repair? I've been thinking about some kind of epoxy resin (like JB weld,araldite,miliput etc) that could be mixed and added to the crack, then re tap the thread to match the resin with the existing cast thread.
what do you think of my plan?

Fri Mar 19, 2010 7:38 pm

plug the hole w/ a pipe plug, then grind a bit on the top of that crack, then fill it with jb weld and hope for the best, it probably wont work, but you have a chance . maybe you can find a specialty epoxy that expands at the same rate as alu, and that would be more successful.

or ask around the local shops untill you can find someone who will weld alu.

Fri Mar 19, 2010 8:44 pm

I would buy a new case or at least split it and let a welder take a crack at it. The oil will have contaminated the area and it may not weld easily.

Fri Mar 19, 2010 8:52 pm

could a timesert work?

Fri Mar 19, 2010 8:54 pm

I'd clean it up with lots of brake cleaner and JB weld the sender in (don't torque it up much), you have little to lose as the next option is another case.
Even better install a tee or elbow so if the sender does ever die you can swap it without disturbing the fix (assuming the fix works, I've seen approx 70% success).

Lesson for other owners, don't overtorque the sender.

Fri Mar 19, 2010 8:57 pm

Thanks so far ! I've found this...Lumiweld,this is probably better than JB etc as its nearer to ali.you're right about the heat/expansion. Its only a small leak so I would like to do all I can to cure it for now.I suppose making sure the surfaces are clean is a must. carb cleaner should do the trick you reckon?
http://www.frost.co.uk/item_Detail.asp?productID=8823&frostProductName=Lumiweld Kit (5 rods)

Fri Mar 19, 2010 8:57 pm

no, it will leak and that is a tapered hole.

The biggest issue is keeping debris out of the oil gallery. If he disassembles the case to be able to work with it then he might as well replace it. It can be welded once it is apart and ground down and re-tapped but all that work and what if it leaks again. He can use telflon and JB weld for a while to slow the leak but I think a new case is his best solution here. I can think of lots of ways to repair it but all of them involve the risk of debris in the oil gallery.

Sat Mar 20, 2010 12:17 am

The aluminium repair rod will work fine, but it is going to be hard to tin the area as you can't get a wire brush to it to clean it. This stuff makes a very strong repair that shouldn't fail with time. You might be able to do it without splitting the case, but if you get one drip of the aluminium solder into the galley you will waste out your bearings.

I think this is what I would do:

***Split the case
***Clean the crack as well as possible. It wouldn't hurt to open the crack up a bit.
***Insert a pipe nipple or 10x1mm bolt loosely into the threads. You may need to make some kind of a dam to prevent the solder from flowing out the end of the crack. A nut threaded onto the bolt would probably do fine here.
***Solder up the hole being mindful not to overheat and melt the case.
***Remove nipple or bolt and clean the threads up with a tap.

Sat Mar 20, 2010 1:03 am

As far as welding is conserned the case is magnesium not aluminum thay weld abit diffrently. But I think most here know that.
http://www.weldingtipsandtricks.com/welding-magnesium.html

Sat Mar 20, 2010 1:58 am

As far as opening up that crack any more... I wouldn't suggest it. Looking closely you can see that it's already developing a sideways crack at the end of the primary crack. That engine needs to come apart for replacement or welding; obviously your welder should be informed/aware that there's a high percentage of magnesium in the case alloy.

If you're not ready for a teardown & repair/replacement just yet, you might want to: 1) go with the carb cleaner or quick start/ether spray to get the metal as clean as possible, 2) work your favorite Lumiweld or JB-like epoxy into the crack to seal it up, and 3) immediately cinch around it (not too tight) with a narrow hose clamp.

After the epoxy is cured, use chassis lube grease on a 1.0mm x 1 tab to lightly chase the threads in 5mm or so; the grease will help to hold any chips the tap will cut loose. Solder a ground lug/tab to the one of the flat hex wrench surfaces of your pressure sensor, then use a reasonable amount of teflon tape to seal the threads before you screw it in, again not over-tightened. Connect your sensor to the wiring loom lead, and connect a jumper wire from the new ground lug to a bolt on the engine tin.

There are electrically-conductive sealers, but the teflon tape may have less chance of sending funky particles roaming around your engine's oil passages.

As to the crack's cause, if your bus was in the US, I'd almost bet that at some point, a p.o. was sold a 1/8" NPT sending unit to work with a pressure gauge... instead of a properly tapered 1.0mm x 1 threaded sending unit. The 1/8" NPT screws in, kinda, but it virtually always seeps/leaks, so many folks just 'use a bigger wrench' to tighten it up until there are no more threads left, the case cracks, or both. OTOH since you're on the other side of the pond, likely it's just plain over-tightening, unless a similar 'close' mismatch exists with one of the BS thread pitches.

Good luck.

Sat Mar 20, 2010 2:28 am

The english BS or W thread's have the same number's as us 3/8 5/16 on and on but thay are at 55 degrees thread pitch and we are at 60 degrees same with metric 60 degrees. I work on old brit cars and bikes in my shop along with vw's so the last time I went over I picked up a load of old tools and tap/die sets. In England BS or W are not used anymore that I saw when I lived there Just on old stuff.

Sat Mar 20, 2010 7:41 am

There is a product called plumbers epoxy, you can get it at plumbing wholesalers. It sets hard as a rock, it can be drilled and tapped. Years ago I plugged a hole in an aluminum motorcycle engine with it and it held good. Different expansion rates didn't seem to affect it. The key to using it is to get the surface very clean. Silicone might be another option, at this point what have you got to lose. :bay_red:

Sat Mar 20, 2010 7:53 am

[quote="wampe"]There is a product called plumbers epoxy, you can get it at plumbing wholesalers. It sets hard as a rock, it can be drilled and tapped. Years ago I plugged a hole in an aluminum motorcycle engine with it and it held good. Different expansion rates didn't seem to affect it. The key to using it is to get the surface very clean. Silicone might be another option, at this point what have you got to lose. :bay_red:[/quote

It's made by Harvey's and Oatey.

Sat Mar 20, 2010 8:14 am

bigbore wrote: As far as welding is conserned the case is magnesium not aluminum thay weld abit diffrently. But I think most here know that.
http://www.weldingtipsandtricks.com/welding-magnesium.html

You are right of course. I forget these things are magnesium and not aluminium like the T4's. :oops: In that case I can't say how the aluminium welding rod will work because I haven't tried it on magnesium. May work fine, might not work at all.

Sat Mar 20, 2010 11:12 am

Thanks guys you've been a real help! So it seems long term the case will need to be split.seems a shame to do it just yet as the engine is nice having only done 89k.
So I guess its just a case of choosing the best product to plug the gap for as long as it lasts!

Thanks guys, will let you know how I get on when I get round to it.

Sat Mar 20, 2010 4:57 pm

An engine I had a few years ago ran fine but had the same oil leak and crack as you have and the threads were half striped.
I took a piece of 1/8 inch brass pipe and after cleaning the case used the 5 minute J B Weld and put a thin coat on the pipe threads before I screwed it in and then put a small coat on the outside. Then I used a union and screwed the sender on. Even though the threads were off a little on the sender it tightened up and didn't leak and I could still change the sender.
5 years later was still holding with no leaks.

Fri Mar 26, 2010 5:58 pm

the permanent union is a good idea ,but...
what about lead loading it? a mate does lead loading,if we ,heat up the area put the pressure switch in place and run hot lead into the crack,surely that will fill all the gaps? let it cool,un screw the pressure switch and hey presto. I wouldn't have thought the engine block gets hot enough to melt the lead would it?

Fri Mar 26, 2010 7:20 pm

No, but how can he guarantee the lead is going to stick to oil soaked magnesium and stay stuck under pressure? Also can he guarantee not a drop will enter the oil gallery that sender screws into?? If you are considering that you're better off with the JB weld and short fitting route, that stuff sticks to freshly cleaned magnesium and like Tom62 I've seen those repairs last many years. Hot lead on cold metal casts itself to the rough surface of the crack but will not stick unless the entire case is heated to a temp where soldering would take place (even then it may not), not only would that be bad for the rest of the engine I'm still not sure it would be compatible.

Fri Mar 26, 2010 9:00 pm

Lead is a bad idea. stick with JB weld.

Sat Mar 27, 2010 1:21 am

OK guys, Thanks! I think you're right,union extension is the way to go with this. so where do you think I could get the right threaded union from? is it something a plumber would use or an auto mechanic?