I have a 67 Jaguar 340 which is leaking a bit of oil - possible from the rear mail seal. I'm aware that radiator sealants are a no no for classic jags but has anyone ever made use of an oil sealant kit ? (products like 'Blue Devil') Is this also potentially bad for the Jag ? Any advice would be much appreciated

 

If it's still the rope seal in there, then I doubt it will do much good, if it's been changed to a modern seal, I still don't think it will help.
Modern seals leak because they simply wear out, the lip that rides on the crank shaft wears down and no amount of softening the seal will help to keep it from leaking.
Will it harm the engine, I don't think so, it does not have hydraulic lifters with tiny orifices that will plug up from the "stop leak" additive.
It won't hurt to try it, but I don't think it will do anything.

 

Thanks very much for the swift reply

 

Glyn will give you more info regarding oil leak addictive's as that is his field of expertise but my view is that a anti leak addictive is like taking an aspirin for a broken leg. Yes it might help but it will not cure the problem. Same with radiator leak stop.
The oil leak addictive's might also cause you more trouble down the line as they will block oilways, maybe only slightly but they will stick to the sides of the pipes and then you have the equivalent of blocked up arteries around the heart. Sooner or later the oil is not going to flow to well and the engine is going to start to overheat. A large percentage of the engines cooling is via oil flow not just water.
All old Jaguars leak fluids either from the engine, gearbox, rear diff or power steering. They used to say that the oil leaks were designed in to the Jaguar as an anti rusting agent. If it is sever though the only course of action is to strip it down and fit new seals or gaskets.

 

At best, additives that swell rubber seals give you a few weeks. If it's the rear crank seal, I'd check the crankcase ventilation first.

 

If we are talking elastomer (rubber of many types) seals ~ seal swell additives can be used to stop a leak but it should be understood that this is a band aid & ultimately the seals will require replacement. All one is doing is delaying the inevitable. Seal replacement. These can last a while at 2% by mass treat.

The rear crank seal, unless converted to an SKF Flex Seal which requires machining the crank to 3 inches to remove the scroll ~ which is highly unlikely to have been done to your engine, will not react to any sealant other than those that thicken the engine oil which is not recommended under any circumstances. The rope seal requires to be replaced.

I am a Tribologist. See:


https://www.jaguarforums.com/forum/m...l-seal-244254/

 

Yes, that sounds like good advice. I guess I need to keep an eye on it and how much I'm having to top up. Thanks again - always learn alot from people's comments on here

 

I'm not sure if the seals are the rope variety or have been replaced. So, presumably, either way an additive shouldn't do too much damage (although Cass urges caution here). If I was forced down the band aid approach, is there a specific product that might be more suitable for the jag or are they all similar ?

BTW what's a tribologist ?

 

Thanks Peter

 

A Tribologist is someone that has studied the reaction & lubrication of 2 pieces of material in relative movement/motion to one another & wear. The subject is broad & covers everything from lubricating your engine bearings to the lubrication of Prosthetic joints by bodily fluids.

 

And I thought it would be more anthroplogical ! Sounds interesting

Any preferences for additives ?

 

Under no circumstances try and stop oil leaking from the rear cranshaft seal with Mickey Mouse, off the shelf products, at you local auto store. You can do other damage. Replace the seal. If you are going to retain the rope seal as I have with no leaks follow the manual meticulously. On no account trim the seal ends. Work the seal into the groove with a wooden hammer handle or similar.

 

As far as I'm concerned they are all junk. If you must for elastomer seals only, then Lucas Oil stop leak products are about the most honest in their claims.

I'm fully aware that you can't get seal swell additives that an oil company can source for it's products where minor seal swell can be of benefit or is mandated by an OEM like Poclain.

 

Glyn, just a couple of further quick questions if I may. At what point should one consider replacing the seal ? Currently, I don't have to top the oil up much if at all. I just notice that when the engine is hot I'm getting about one drop of oil per minute on the ground. A garage has told me it's the rear seal. Will the leak be less when the engine is cold ? Presumably it's a fairly big job to replace the seal. Would you do this as part of an engine rebuild ? Apolgies for my rather sophomoric questions

 

Unless there are other reasons for rebuilding the engine, I'd not worry about the crankshaft seal. To me, it's not worth the effort. I would check the breather on the front of the cylinder head and the tubes joining it to the inlet plenum. If they are blocked, pressure in the crankcase can make oil leaks worse. I think some of the E-type owners have gone as far as to convert their cars to modern crankcase ventilation systems with PCVs. It's extra complication most likely for not a lot of gain.

 

Thanks so much, that's really useful.

 

What Peter said,

 

Has the car sat for an extended period previously? I have found that if a car has sat for a long time ( years) and then is driven again the seal leaks and with more driving it will quit leaking on it's own. The camshaft oil feed pipes are at the rear of the engine too, so a leak from them can drip down the rear of the block to the same area as the rear seal.

 

Yes ~ As a rope seal dries out through standing for a long period it will shrink slightly & leak. With daily use oil will once again impregnate the seal & can slow or stop the leak.

 

Thanks again