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MG MGB Technical - Front oil seal replacement

How difficult is it to replace the front oil seal with the engine in the car?

Oil is spraying past the front seal on the rebuilt V engine in my 1970 B. I am using a Weber carburetor and adapted a Toyota PCV valve to try to keep a vacuum on the crankcase but oil sprays from behind the front crank pulley. The car is used for long highway journeys and arrives with an oily rear license plate.

I am hoping that engine removal can be avoided but it is leaking badly enough that it needs to be repaired. Oddly enough, oil consumption on the dipstick is minimal. A little oil goes a long way on the garage floor.
Glenn Mallory

Easy job --
Remove the fan and w/pump pully for easier access-,Front pully off , remove the cover, replace the seal, new gasket , check the cover face to make sure it's flat and good, make sure the oil slinger disc has been refitted to your crank when your engine was reco'd ---if not, you need one
It's possible that the cover / seal wasn't centred up on the pully before---so
Cover on ,leave the bolts loose , slide the pully on through the seal and wriggle the cover a bit to centre the seal up, do a few bolts up a bit trying not to move the cover, then you can slide the pully out and tighten it all up , refit the pully and finish it off, fan,belt etc.
William Revit

Glenn-
The oil seal should be installed into the camshaft drive chain cover/timing cover so that its open end with its spring will be facing toward the crankshaft. Do not attempt to seal it to the cover by means of a silicone sealant of any type. Excessive swelling of a shaft elastomeric lip of a seal is a good indicator that the lip material and the sealant that is being employed are incompatible. Swelling of the seal material can be particularly problematic if some materials, such as silicone, come into contact with oil at high temperatures. Under such conditions, softening, swelling, and reversion of the seal material can occur. Instead, apply Loctite® Hi-Tack.

Clean the camshaft drive chain cover/timing cover thoroughly of all of the remnants of its old gasket, and then apply a little Permatex® Ultra Black RTV Gasket Maker sealant onto the outer edge of the new gasket. It will provide a good seal that can easily be pulled apart once the fasteners have been removed. Adhere the new gasket into place on the sealing flange of the camshaft drive chain cover/timing cover, carefully aligning it with a few machine screws in place, and then promptly remove any excess sealant that has oozed out from beneath the gasket. Sealant should not be applied on the other side of the gasket that faces against the front engine mounting plate as it could then cause future trouble during the next disassembly, risking distortion of the sealing flange of the camshaft drive chain cover/timing cover should you be forced to pry it off of the front engine mounting plate.

Install the camshaft drive chain cover/timing cover onto the engine, using a thin coating of either Castrol® or Lucas® Red Rubber Grease in order to lubricate and thus protect the lips of the oil seal during installation. Leave the machine screws loose so that the cover can float on the end of the crankshaft. Note that the OE crankshaft front oil seal for the camshaft drive chain cover/timing cover tends to leak engine oil because there is not a built-in device for ensuring that the oil seal is accurately concentrically-centered with the rotational axis of the crankshaft after the oil seal has been replaced. A special factory service tool that is slipped onto the crankshaft and into the oil seal after the camshaft drive chain cover/timing cover is installed, but before the camshaft drive chain cover/timing cover machine screws are tightened, was employed at the factory in order to accomplish this. However, I have never seen this tool offered for sale in the United States. However, there is an effective substitute: the crankshaft drive sprocket (BMC Part # 12H 4201, Moss Part # 460-425) for the B-Series engine’s Simplex, i.e., single-row, camshaft drive chain. When its tapered end is slipped onto the crankshaft and into the oil seal, it will center the oil seal perfectly while the camshaft drive chain cover/timing cover is being torqued. Note that the Original Equipment harmonic balancer/harmonic damper pulley wheel has an extension that extends through the seal that is located in the camshaft drive chain cover/timing cover, shoulders against the oil slinger, and clamps the crankshaft drive sprocket into place. This extension provides the sealing surface for the oil seal. Thus the oil seal actually seals against the back flange of the harmonic balancer/harmonic damper pulley wheel, not against the crankshaft.
Stephen Strange

What Willy said.
Dave O'Neill 2

I think you will find that the front anti roll bar is in the way of removing the pulley - it is easier to just undo the four bolts holding the anti roll bar brackets to the chassis rails and pull the bar down than it is to undo the engine mounts and lift the engine!

However it is lots easier if you take out the radiator.

Personally I would not disturb the front cover, but lever out the old seal and press in a new one, no sealant is required on the seal.
Chris at Octarine Services

Agree, a lot easier with the radiator out, but on my CB roadster it was the rack I unbolted and pulled forward for the pulley to clear it, not the ARB. Left the track rod ends attached, the wheels just toed in even though they were on the ground.
paulh4

The reason I thought it better to remove the cover is that it may have been secured at the rebuild without the pully in place and not have been centred up to the pully making it leak oil by wearing the seal on one side---?
Would also depend which cover it has as far as flicking the seal out from the front, some covers have the seal entered from the rear-
Probably 9 out of 10 pullies come out without an issue, usually if you get one that binds up on the rack, a gentle push backwards on the engine with a suitable lever by your assistant while you get the last little bit saves a lot of unnecessary work
If you had one that was really close then maybe the rack would need unbolting off the crossmember to get a bit extra wriggle room but I can't recall ever having had to do that-
willy
William Revit

Thank you!
Glenn Mallory

It was not difficult to replace the oil seal and timing cover seal following the indications above. The old seal was rock hard and cracked, obviously it was not replaced when the engine was rebuilt (???). After a 5,000 mile trip across the U.S. and back, the seal and timing cover gasket are completely dry.

While the crank pulley was off, I installed a larger late model pulley in order to run the A/C compressor at a higher speed at idle. The larger pulleys were obviously used on later cars with electric fan motors as the fixed fan now creates lots of noise at speed. Otherwise, OK.
Glenn Mallory

If the engine was rebuilt just recently It could be that the builder didn't centralise the oil seal on the pulley before tightening the timing cover screws and bolts.
You might get away with centralising it properly.
Allan Reeling

Glenn
The later B's with the larger crank pulley also had a larger diameter water pump pulley--most of them are double V's but really they are two singles (usually stuck together with paint but will come apart) just use the one you need
If you got yourself one of those it would quieten your fan back to how it was before
If you do, there is a plate on the front of the pulleys as well that is needed to support the larger pulley
The racers here use the large w/pump pulley and the small crank pulley to slow the water pump flow down for better cooling
William Revit

I could get the front pulley off my 71 without undoing the rack. I may have lifted the engine a little. I did have the radiator out.
Paul Hollingworth

The oil seal was rock hard and cracked. It came out in pieces, mostly little hard chunks. The seal could only have been at least 50 years old. On a good day. The timing cover gasket was also leaking as the metal surfaces had not been properly prepared for assembly. I am not sure that the gasket had even been replaced as it was firmly stuck to the block.

I took great care to clean both the timing cover and the block, to use an appropriate sealant, to insert the seal into the cover carefully and to center the cover with the pulley before tightening. After a 5,000 mile trip, there is no sign of oil whatsoever from either the timing cover or the seal.

Access to the crank pulley was not difficult and I had high hopes for being able to remove it without dismantling the engine compartment. Loosening the bolt was tough. It ultimately required removing the radiator, water pump and moving the steering rack to get a handle long enough against the bolt and socket. There is enough flexibility in the prop shaft that it took rolling the car in 3rd gear break it loose. The impact wrench was of no use. The torque setting is 70 Ft/Lbs so maybe next time it will be easier. It must have been assembled with an impact wrench and out-of-control air pressure.

It is always best to do this work myself. Next time.
Glenn Mallory

My crank pulley nut was cranking the car forwards in 4th. Impact gun no good either. I put some padding on the LH chassis rail, a tommy-bar in the socket about an inch from the rail, and flicked the starter (out of gear by then of course ...).
paulh4

I always use the starter trick to undo crank bolts if the engine is in the car.
Chris at Octarine Services

And it's a supposed rebuilt engine????
Allan Reeling

I use a metre long bit of pipe (aka the Vogon bar) slipped over the breaker bar and the handbrake on hard (or on bad cases a helper with four on the brake) . Never fails.

One point to watch: the covers have often been distorted by incorrect seal removal or fitting in the past, with the result that the seal is no longer parallel to the front plate, so runs at a small angle to the crank. Easy to rectify by massaging the cover, and a potential fail source of left unattended.
Paul Walbran

Guys
You need to get a power bar like this-----
Mine just has powerbar written on it
Just push on the handgrip a bit to take the slack out and whack the red bit with your favourite thumper--worth it's weight in gold
AND , by the way, the starter motor method might be ok for MGs but don't do it to later VWs and probably others. The vw doesn't have a crankshaft keyway, just a little pimple on the face of the timing sprocket that goes in an indent on the face of the crank--You can imagine what happens if you flick the pulley bolt out with the starter, yep head off new valves


William Revit

I had the timing cover off several times trying to cure a bad oil leak thinking it was the front oil seal. Turned out to be the cover which was distorted. Reinforcing plates I got from the US has cured it. Put photos on my blog at https://mgb.tips/category/projects/timing-cover-oil-leak/ . The flange around the cover gets bowed due to overtightening of the bolts.
It's a nice bit of well made kit.
steve livesley

This thread was discussed between 25/01/2020 and 18/03/2020

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