21 replies to this topic

[peasoup39]

Just bought a  1978 clubman for restoration. It has a very smoky engine. Very Smokey which i know is a common trait on these engines.

Previous owner says he changed the head in case it was valve stem seals but it made no difference.

Just done a compression test and all cylinders are above 13 bar (185psi) which is i believe is very good..

If i remove the oil cap whilst running there is no change in engine speed which suggests the crankcase vent is  gummed up but would not think it would cause that amount of smoke.

Car has only covered 1700 miles in the last 5 years which may suggest gummed up rings but this would not give this compression or would it.

I plan on putting Redex in the bores for a few days to loosen the rings otherwise its a complete strip down.

Its 50 years since i played with one of these engines so has anyone got any suggestions on what it might be?

[MiniMadRacer]

That PSI is very good esp if its even across all 4 cylinders... when does it smoke... start up, acceerating, on the overrun ?

 

What oil are you using?

 

Does it smoke consistantly hot and cold?

 

What colour is the smoke?

[Cooperman]

The compressions look fine, but it could still be bore wear.
Get the engine up to operating temp and let it idle. Remove the oil filler cap. If it 'puffs' smoke out of the hole there is excessive bore wear.
It is unlikely to be valve guide wear if it is very smokey.
Yes, it could be sticky rings, but that is uncommon and pouring some diesel down the bores and letting it soak in should ensure that is not an issue.
You could do a 'leak down test' which is better at identifying excessive bore/ring wear that a comp test, or simply take the head off and inspect the bores for wear at top, bottom & centre of stroke which will give an answer.
The old 1098 is a long stroke engine and will tend to burn more oil than a 998, although it should be no worse than a 1275.
If you take the head off you can fit the latest valve stem oil seals.

[Maccmike8]

Could be shockingly bad carb set up.

[peasoup39]

I have only just bought the car so only had it ticking over on the drive or100yds up a private road and back but in answer to your replies.;-

Don't think it is the carb. It will not start easy from cold without the choke. With choke it fires up instantly and settles into a nice tickover .However my next job when running is to adjust the mixture.

Do not know what oil is in it as not yet changed it myself.

It does not smoke on tick over but smokes very badly on reving. It is blue smoke and is so bad i would be stopped by the first police car that sees me on the road.

If i remove the oil filler cap there is no puffing out of fumes or smoke or signs of positive pressure if i put my hand over the hole. The engine speed does not alter. which suggests blocked breather which i will see to next.

Currently the bores are being soaked in Redex for the next week to try to clear rings. Did not realise i could use diesel.

As previously stated it has only done 56k miles but only 1700 in last 6 years so gummed up rings may be an issue.

When rings are soaked i will do a leak down test as i can use my compression tester with the button held open

If the above does not improve the situation it will be head off and check bores but would prefer not to if i can avoid it.

[Maccmike8]

Could the damper oil have been over filled and oil is sat on the carb mouth?

If not the carb the most obvious candidates are valve stems/seals or rings. 

Valves might need reseating, unburnt fuel going through will smoke.

Keep us updated.

[MatthewsDad]

I'm dealing with a very similar problem on an mg at the moment. Very good compression readings and professionally tuned twin carbs, but lots of oily smoke. Consensus from having consulted a couple of engine builders is oil ring failure. The car was sat unused for many years.

[leyland73]

I'm dealing with a very similar problem on an mg at the moment. Very good compression readings and professionally tuned twin carbs, but lots of oily smoke. Consensus from having consulted a couple of engine builders is oil ring failure. The car was sat unused for many years.

Yep my 1100 special has 8k miles from new, but spent its first 15 years of life in a museum. Itd used about two pints of in the 1k miles I've put on it since purchasing it 3 years ago.

I think when new it wasn't properly run in on load as most cars would be and spent time under choke being moved around the museum, hence bore wash and badly sealing oil control rings. Can't have it all, still love it to bits.

[blacktulip]

Have you given it a run out yet? I doubt an officer would stop you if you have a smokey engine. See what happens

[Maccmike8]

They will if its really bad, seen it on telly multiple times.

[DB1380]

I think i'd take it for a little run very early in the morning when its dark....give it a little bit of an Italian TuneUp !! lol Kill or Cure.

[gazza82]

They will if its really bad, seen it on telly multiple times.

Just make sure the TV cameras aren't around

Edited by gazza82, 23 November 2020 - 04:51 PM.

[jaysmini1983]

I would change the oil and take it for a drive. legally as possible.  

[bpirie1000]

Any chance of any oil being in the exhaust ?

Burning off with the heat of the engine.

[peasoup39]

As previously mentioned i  soaked the bores in Redex for a week and did a compression test and all cylinders were 13 bar plus. It was suggested i do a drop leak test as this would tell me more about the state of the valves and bores so i purchased a test kit.

Contrary to instructions i did the test on a cold engine and had not run it to burn off the Redex.

Cylinders 2, 3 and 4 all showed in the green band which is good but cylinder number one has puzzled me.

On first test leak gauge went straight to the red band (bad) and i could hear the leak coming from the plug hole on cylinder number 3. I cannot see the connection with cylinder 1 leaking across to number 3 cylinder presumably above the piston.

I turned the engine over a few times and retested number 1. the leak gauge just went out of the green into the yellow which is acceptable and no sign of leakage into number 3 cylinder.

Unfortunately on starting the engine and running for long enough to burn off the redex effect it is still smoking as badly as before. No smoke on tickover but lots of it on reving .