Smelly engine

[houseamber]

Dear All, Hoping you might be able to shed some light on a niggling problem!
We have two moggies - one with a 1098 1962 engine and one with a 948 1962 engine. Both are daily drivers.
The issue is the 948 smells much more fumey than the 1098 and seems to discharge visible white smoke at times.
In every other way it drives really beautifully and has good spark plug colour and fuel, water and oil consumption (though we find it more difficult to read the oil level in the 948). We also had the head rebuilt late last year.
It's so bad that my children comment on it!
Is this a 948 thing? If it is running fine, do we ignore it?
It is driven a lot and never misses a beat so up until now we've just carried on!
Any thoughts?
With thanks in advance

[oliver90owner]

If there are no exhaust leaks, I would suspect that the engine breathers are different, or one is working and one is not.

The other alternative, if both are breathing to the atmosphere is that there is easy access for fumes to reach the interior in one and not the other.

The last is one of the exhaust pipe exit area - can exhaust gas get drawn in at the rear on the ‘smelly’ one?

I can’t think of any other alternatives other than these obvious possibilities (from your description) assumingnyou mean the smell is detected within the car while driving.

Back to you to investigate.

[les]

Yes, I would also suggest the last option mentioned, I had a similar issue with a small gap in a tailgate seal, when driving with a partially open window, fumes entered.

[Nickol]

Does not white smoke in exhaust indicate that water is getting into one or more cylinders?

[houseamber]

Thanks all so much, we inspected the spark plugs again today ( though still running fine) and plug no 3 is now black and covered in deposits and has damage to it (see photo). All the others are a lovely shade of light brown. We've changed the Spark plug now.

The breather on the smelly one is a canister type (the 1098 doesn't have this) we have breathed through it and it is running clear, but I would think it is probably ancient so as you suggest, maybe that is the problem?

[oliver90owner]

If that plug is indicating excessive oil burning, there may be other engine problems.

Piston ring(s) on that cylinder could be worn/broken, leading to excessive oil consumption and blow-by to the crankcase. Excess blow-by could cause fumes reaching inside the car.

Oil pouring down a worn/damaged valve guide, and/or perhaps no oil seal could be causing the oily deposits on the plug.

More investigation required.

[houseamber]

Brilliant, Thank you - sounds like a plan

[mowogg]

Before you get to I grossed in the engine I would check the manifold to exhaust pipe seal. These frequently leak in my experience and can be really difficult to deal.

You can often see it when you start it up. If you look at this area when the car starts you often see a puff of smoke which then comes out at other times. This then can migrate into thr cabin through a variety of holes in thr engine bay

That said the spark plug issue needs a little further r investigation

[houseamber]

Thank you - yes a great idea, we'll check that in the morning
Our experience, like yours are that they are tricky to seal well. I'm hoping it keeps going a bit longer before we enter the realms of major overhaul!

[mowogg]

Just re read this. You said the 948 has a canister type oil breather. This is non standard as these were fitted to late 1098 engines that the fumes are taken to an extra intake on the carb.


Where is the canister plumbed into? To work effectively it needs to be routed to the carb. And it should also have a breathing type oli filler cap.

If it's not connected to the carb it could well be the issue. Depending on the rest of the set up it is possibly easier to covert back to standard

[houseamber]

Interesting and curious - I wonder why that was done if it is not standard for that car? It is connected to the carb and the tappet gantry cover. We recently (couple of months ago) changed the oil cap to a breather type, having read posts on here about oil cap types, so perhaps it will improve with time.
Since my post the green light has started to come on briefly shortly after start up (after it goes out initially)and then goes out again once it is warm. The new spark plug is now oily, so I think we've concluded that it needs more investigation by a specialist, though the smell may be unconnected to the engine issue of course!

I'll let you know the outcome
Thankyou