It seems that the sump got damaged when driving over a branch or something similar. The seepage is minimal, nothing on the driveway. The crack has been discovered during routine service when the mechanic saw oil on the plastic sump cover. The sump is not under stress, the oil there is not under pressure, and replacing the sump will cost an arm and a leg. Can I somehow stop the seeping? It almost calls for a gaffer tape (just joking) but perhaps there is a sensible trick to fix something this minor. Please advise.

or something similar. The sump is not under stress, the oil there is not under pressure, and replacing the sump will cost an arm and a leg. Can I somehow stop the seeping? It almost calls for a gaffer tape (just jpking) but perhaps there is a sensible trick to fix something this minor. Please advise.

The oil in the sump is not under pressure?

I guess the weight of six odd litres of crankcase oil in a wet sump engine cannot technically be labelled as "pressure"

It's an oil leak. However minor or major, a leak is a leak is a leak

If you can live with it, just keep topping up your oil as it gets low (I hope your garage floor isn't nice and clean) There won't be an easy or cheap fix though the metal is cracked and it's not something you can just patch with chewing gum

If the crack is in the bottom, I agree that the weight of oil creates pressure, even if small. Here the crack seems to be high up on a side wall, so no pressure, just sloshing. Not a single drop on the garage floor, I would not know about it if the mechanic did not tell me. Still, I do not like it and would rather deal with it somehow. A leak is a leak is a leak, no disagreement here.

Any ideas welcome, I will try any sensible suggestion. If nothing works, there is always the fallback option of replacing the whole sump.

I wish the sump was pressed steel not a sand cast prone to cracking.

I've done a temporary repair with "knead it" on my c30 sump previously.

If you clean it up thoroughly, and scuff the surface with sandpaper you can get a decent bond, but I still replaced my sump a couple of weeks later.

Might be worth checking your engine mounts as the driver's side hydraulic mount can sag and the engine drops, also you can get an alloy undertray from Volvo so it won't happen again.

Hi Andrew,

Worth talking to someone with experience in welding aluminium, If it works great, if if the heating causes the sump to warp then you start again. If the car is jacked up and the oil drained, and positioned so any oil left over does not build up near the crack. An experienced aluminium welder could weld the crack with a series of strikes waiting between each strike to cool down. Take time but worth a try. Where are you located.

Welding will be a difficult task, as the aluminium will have absorbed some oil, and will need to be thoroughly cleaned out before a good weld can be performed.

This usually involves soaking in degreaser and/or running an oxy torch over the area to be welded.

I have had reasonable success with Knead It, but again: cleanliness is key. To do a good job, you will want to remove the sump, thoroughly degrease inside and out, and then thoroughly clean with brake cleaner or similar.

If you leave the sump on the engine, then you will need to work hard at ensuring that oil isn’t weeping through the crack while you are applying the putty and it is hardening. I have done it a few times, usually by flushing the inside of the sump with copious quantities of brake cleaner, but the results have varied from “excellent “ to “mediocre”.

At least your crack is not catastrophic, so if the repair fails it is only going to weep again (rather than dump the entire contents of the sump onto the road in three seconds).

Our S40 has a welded sump. Looks like it's taken a thump in a previous life. (30,000km engine out of a wrecked C30...was in a hurry to get the engine swapped over and the car running again).

I kept the old S40 sump to swap over when I get around to buying O-rings and gaskets but I'd forgotten about it until your post. Never leaks oil, but I feel bad knowing I have an undamaged sump corroding away under the house somewhere.

My point is - it can be done and there's no reason not to have a go first. Worst case you need a sump - but they should be readily available used and they're reasonably easy to replace in the car by the looks of it.

Clean up area.

If a crack apply Balzona or other brand metal putty after good clean , leave it rough.

If a small hole drill and tap a shallow thread (or all the way if confident on getting swarf out of it out the drain hole) and Loctite a thread into it.

Either is fine and good enough for life.

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