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MG MGB Technical - Oil Leaks, MGB 3-main Engine

Oil Leaks, MGB 3-main Engine

I realize that oil leaks are common on MGs, but my 3-main engine leaks are excessive and come from three areas; the rear main bearing, the oil pan gasket and from the oil filter where the rubber seal on the filter mates with the sealing surface on the oil filter spin-on adapter (not he adapter to engine block interface). I have read the many oil leaks comments on the many forums including the MG Enthusiast’s and have even requested information on a previous forum. All have been helpful but before I make a serious attempt to resolve the problem I need additional information and am hoping that some of you can help.
1. If the rear main is leaking, on what external parts of the engine should I see the leaking oil? Would it be on the front side of the rear engine plate, between it and the block and oil pan or should it be coming out of the drain hole in the bell housing? If oil is coning out of the bell housing hole does this mean that the shallow slot on the front of the rear plate just below the large center hole has been blocked (with sealant) thus preventing the oil from draining back into the oil pan, forcing the oil over the center bore and into the bell housing?
2. With respect to the straight cork gaskets that are fitted at the front and rear of the engine, how should they be oriented? They are rectangular in shape, not square. As a point of reference, if the engine is oriented upright, as if in the car, should the long length be horizontal or vertical?
3. If these front and or rear cork gaskets are installed incorrectly and thus leaking, where should I see evidence of the leak on the external parts of the engine?
4. What are these gaskets actually sealing against? They are supposed to prevent oil from passing from where to where???
5. The oil pan leaks at the front and rear of the pan may be the result of the cork gaskets being installed incorrectly (the reason for my asking question 3). If the cork gaskets are not the problem, I was thinking that a solution was to first ensure that the pan sealing surface was flat and none of the screw holes are dished due to excessive torque being applied in the past and then make a gasket from 1/16’ rubberized cork material or silicone rubber, if available. Is this a good idea? What material is preferred?
6. The oil filter and the adapter really have me perplexed. When first purchased and installed, I found that the Wix filter, when screwed on to the adapter, bottomed out (metal to metal) before sealing. To solve this problem, I made a spacer from two pieces 1/16 rubberized cork gasket material and an aluminum plate both circular in shape to match the diameter and width if the adapter’s original sealing surface. I used epoxy to glue the spacer to the adapter. The filter no longer bottoms out, but, nonetheless, still leaks at that interface. Can someone shed some light on this?

Any and all comments will be appreciated.

Frank Grimaldi - Beaufort, SC USA
Frank Grimaldi

Frank. No comment on the other leaks but with the filter you need to get the correct one. If it bottoms out then the filter cartridge is wrong. The instructions with mine clearly state that the rubber sealing ring on the filter should be about 1/8" proud of the body.

There are various lists of suitable filters. Here is one

http://mgaguru.com/mgtech/engine/of100b.htm

Tony
Tony Oliver

Frank, I have found the instructions for the adapter supplied by Moss. It states

"In the filters we offer the lip of the threaded hole is .113 to .125 BELOW the surface of the rubber seal. If the lip of the threaded hole sits too high it will bottom out against the shoulder of the adapter bolt before the rubber seal contacts the surface of the adapter"

This sounds like your problem.

Hope this helps.

Tony
Tony Oliver

Frank,

I think Tony has you covered on the oil filter. That is, if you have to make up extra parts, it's the wrong filter.

If the oil pan is puckered from over tightening, I would fix it with a hammer. I think this is better and faster than trying to make a special gasket. Just get a solid surface to fit on the bolt side between the raised stiffening ridges, and smack the block side of the pan with a hammer.

As for the cork, I know what you mean, but I can't remember for sure. Also, my experience was with a 5 main bearing engine if that makes a difference. I do remember thinking about which way the cork went, and I vaguely remember that the long part was horizontal. I think one way was a tight fit, but the other way left a gap.

Sorry that I can't be more sure. I'll bet you get a definitive answer soon.

Charley
C R Huff

My best answers to
#1: If the Rear main oil seal is leaking, I would expect oil to run down the back plate and leak out betweewn the back plate and the bellhousing, or come through to the hole in the bottom of the bellhousing. Rear main seal leaks can happen if there is not enough positive crankcase ventilation, or if there is wear on the crankshaft surface where the seal lip rides against. On my 73B there is a hole large enough in the back plate that I can feel if there is oil running down the back plate. If its really coming out, it may be on the flywheel as well.
#2: When I recently rebuilt my engine, I did not trust the cork gaskets supplied with the set, so I made a pair out of an extra valve cover gasket. I made them about 1 mm larger than their places in the bearing caps in all 3 dimensions. Seems to have worked perfectly. I used Permatex Aviation gasket sealant.
#3: I expect that leaking in these cork gaskets would cause oil to drip from the front (may look like a timing cover leak) or down the back plate (or may look like the rear part of the sump leaking) - but I am not sure.
#4: My guess is that they are to seal the sides of the caps to the block - the rest of the cap's side joints are covered by the front or rear plate gaskets, and the sump gaskets. But I can't be sure.
#5: The biggest problem with sumps leaking appears to be because of overtightening, which makes the holes proud of the rest of the pan. I punched mine back and used a straight edge over each hole to make sure it was perfectly flat. No leaks.
#6: I too suspect the wrong filter.
My car currently has no leaks from the engine. It does however have a leak from the overdrive despite my valiant attempts at sealing it up. At least the oil in it is always clean and clear.

Hope this helps.
Erick Vesterback

The 3 main bearing will leak from the bellhousing drain hole, it has a similar screw return arrangement to the XPAG which is an oil-seal-ish. However I have seen the amount 3 bearing and XPAG engined cars leak and it's tolerable if the oil return is working as designed.
Stan Best

While I am not a fan of silicone sealer, I have found the following to work quite well when needed.
Clean bothe surfaces to be joined with brake clean or other strong solvent. Put a nice size bead of silicone around the pan surface. Locate the pan t the engine with the pan bolts, leave them loose. Push the pan up by hand until it is seated, do not press hard. Turn the bolts in finger tight. Now leave it sit for 24 hours so the silicone will cure. Tighten the pan bolts as normal. By letting the silicon setup overnight before tightening the pan will allow it to cure so that when you tighten it down there will be pressure against the silicone helping it seal. Most people put it on and then tighten it tight right away, squeezing the silicone out and leaving it with no pressure once cured. This results in the sealing to be performed by the adhesive properties only, much more prone to leakage.
John H

This thread was discussed between 26/05/2008 and 27/05/2008

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