I'm looking for help with my oil separator/breather box, which appears to be leaking oil from the bottom, where it seals on the block. I posted about this 6 weeks ago, and since that time replaced the o-ring, then the box itself, with no improvement.

The top and forward edge of the box are clean and dry...


but the rear portions and bottom are wet with oil:


That's a brand-new box, installed 2 weeks/1000 miles ago... but it looked like that after driving just a couple hundred miles.

When the box is removed, the areas below, behind and to the sides are wet with oil:


I lost about 1/2 quart of oil over an 800-mile highway trip. The oil is going back along the transmission and getting on the exhaust at the trans-downpipe brace... I can smell it burning on the exhaust.

Today before I put it all back together, I made sure the oil return pipe was clear, and put a little bead of RTV on the bottom of the box around the o-ring and return pipe seal, but after driving 20 miles I had the same leak again.

The return pipe seems snug, but maybe it's not making a leak-proof seal with the block and/or box? I'm stumped.

- Brian '93 945T

I have seen similar issues...

i too went through all the steps suggested (including de-cruding the drain line by passing a peice of 'windscreen washer' tube down it until it would go - boy what a pita!).

with mine it came down to oil colessing in the hose above the box (sort of flame trap area) and running back down the tube into the top of the box, as the tube fits around the box it was dribling down between the tube and the box..thence all over the box. I solved it with a 'jubilee' clip around the tube to create a seal.

Now I DO have other issues with PCV etc and oil use so this may not apply to you - but I also went through multiple boxes and lots of messing about...
--
Old Volvo's never die..they just get more attention!

Hi Brian,

A leak such as the one you are experiencing can be caused by the incorrect placement of the wire harness bracket that you moved aside to lift the breather box out. Make sure the steel bracket is not placed beween the breather box and the block, but placed on top before the 2 bolts are located.

John H from Downunder

Dear Brian S,

Good a.m. and may this find you well. Has this always leaked a bit?

I suspect that the metal surface is not perfectly flat, or, at any rate, not flat enough to ensure a good seal. If the metal surface is "out of flat" -- from the left-hand edge of the big hole to the right-hand edge of the "o" ring in the photo above -- even if you install the "o" ring properly and bolt up tight, neither you - nor anyone else - can get a complete and so lasting seal.

In the last photo, immediately above, the metal at the edge of the bigger hole, closest to the block, seems to be rough.

If you can get a small straight-edge (a machinist's tool, lapped to ensure a "perfect" straight edge) and lay it across the openings, I suspect you'll find a small gap between the edge of the tool, and the edge of the openings. If this guess is correct, then you'll need to polish the high points until the gap disappears.This gap may be a bit too wide for the "o" ring to span, so oil bleeds around the "o" ring.

If the surface is polished, when you bolt-up, you'll get a tight seal. Since it is infeasible to remove the engine and use a milling machine to remove metal, a hand-held stone will have to do. It will have to be laid flat across the opening, and moved side-to-side, with consistent gentle pressure. I'd stuff the openings with rags to trap abrasive particles (and wash the area with brake cleaner afterwards, using "Q" tips if necessary to get it surgically clean.

This is likely to take some time and lots of elbow grease. Alternatively, if the breather box is a relatively cheap part, you might want to shape the top surface of the breather box, to conform to the metal.

Unless the two surfaces - the metal and the plastic - are perfectly flat or mated, you can't get a lasting seal, because the combination of heat and pressure will displace any but the toughest sealants.

I do not know if it is permissible/safe to use a viscous, copper based sealant in this location. Even that may not stand up, if the gap between the surfaces is too large, because plastic - subject to heat - will expand and break the seal.


Hope this helps.

Yours faithfully,

spook

Hi Spook -
No leaks at all at this spot for the first 16 months I owned the car, during which time I did once remove, clean & replace the box. Leaking started ~2 months ago, and has been the same with
+ original box w/ 10-month-old-o-ring
+ original box w/ new o-ring
+ new box w/ new o-ring

You're right about the picture - the inner edge of the larger hole looks rough. That edge is actually machined, but was covered with crud when I took the picture. I cleaned it up nice before reinstalling.

Because I had the same problem with old and new boxes/o-rings, and I doubt the shape of the block suddenly changed, I'm guessing the problem may be with the oil return drain tube, which is made of some kind of flexible rubber or plastic material. Replacing the tube would mean pulling the sump, so I'm looking for another approach to making the tube/box/block seal better...

- Brian

Just finished a similar problem on my 93. The problem in my case was the car is EGR equipped and I had done the first job with manifold on. This unfortunately is nearly impossible with EGR vehicles and I did not get the two little horseshoe shapped brackets properly tightened, in fact missed them entirely. Next problem is the ferrules in the box through which the bolts pass were too tall preventing me from tightening the bolts and box snuggly enough to the block.

Would suggest: take out the ferrules and file them down so you can snug the box better, make sure you have a good O ring, and if EGR equipped, be sure all brackets fit and are not bent.

At this point, one week out, I am not leaking. I also replaced the top hose from the box.

Good luck,

dick

Not leaking sounds good... hope that continues for you. I am going to take a very close look at my "old" box, maybe play with the ferrules as you suggest. No EGR to deal with, thankfully.

I forgot to mention that a year ago I removed & cleaned the original box, and replaced the o-ring, as preventive maintenance... this problem developed without apparent provocation about 10 months later.

- Brian

This is non-pressurized, so any leaks down there reflect a poor seal or a crack in the box. Are you sure the box is tight with no cracks or any pinholes? O-ring in good shape? Bottom sealing surface of box is square and not warped? Top tube is not cracked?

Very unusual leak...

Old and new boxes (with new o-rings) did the same thing... which is making me think about the return pipe as a possible culprit. No leaks above the box... all the other PCV bits are less than 1 year old.

I'll take a very close look at the old box, which is out of the car now, though.

- Brian

Brian,could be the drain line,which you may have knocked out of position-it runs by a clamp.Correctly installing it requires removing the pan!A check could be made-stick the appropriate sized piece of tubing into it with the box removed and blow.There should be no back pressure if you drain your oil and open the oil filler cap.I assume you've checked the rest of the vent system for blockage.A problem with this system I've posted on before could be the drain line collapsing-someone once told me this happens with Volvo fours-it can cause INTERMITTENT oil blowing and crankcase vent problems as the collapsed area opens and closes!I've trotted this out on the board before-never got a response.Anyone? sredwine 94 944T 142K,V90 72K

OK, interesting.

When I was mucking around with this yesterday, I tried poking a piece of wire hanger down the tube. At first it only went in about 3"... I kept poking and eventually got it about 6" down... but still not to the oil in the sump. I found a piece of nylon tubing (about 1/4" OD), and slid that down the return pipe, and it went straight to the oil in the sump... maybe 7-8" down, with little resistance.

When I first started poking with the wire, I thought the tube might be blocked... but the wire may just have been hitting the side of the pipe and getting stuck, I'm not sure.