19 replies to this topic

[Lytesben]

I recently bought a 1990 Mini which I knew was running very rich when I bought it. I put it in for an MOT test just to get an idea of what needed doing and surprise surprise it failed on high Hydrocarbons on the emissions as well as some other bits and bobs. 

 

I got my local garage to go through and change all the bits and pieces that needed doing such as a wheel bearing, brake pipe and also to give it a good tune up and sort out the carb tuning. 

 

They have been through and adjusted the carb, adjusted the value clearances etc and it passes on CO2 emissions but is now kicking out a serious amount of blue smoke from the back end - this seems to be more when it is first started and driven down the road but still some when warm with a bit of throttle. They have run a compression test and inform me that has low compression on cylinders 1 & 2. There is a slight misfire from the engine, but it doesn't seem to be running that rough or much loss of power (saying that I don't have much to compare it to beforehand). 

 

After spending a fair amount getting the rest of the car done I have had to bring it back home for now and try and have a go at sorting the engine ourselves. A couple of people have suggested head gasket, but I can't see any gunk around the caps or mixture of oil/water so could this still be the case or am I more looking at value/pistons? 

 

Any ideas as I have my L2B ticket next month and would love to do it in the classic rather than my new MINI.

 

Couple of quick videos of engine running and the blue smoke when warm:

 

Edited by Lytesben, 23 April 2015 - 11:58 AM.

[Broomer]

How many miles? and how low compression?

[Mr Dave]

Oil could come in through inlet valve guide bores if guides/valves are worn or stem seals are shot. Usually with this it will draw oil in on low throttle (when there is lower pressure in inlet port), then you get a massive cloud when you open it up as it burns. Doesn't account for the compression though (unless valve seats are coked up and not sealing properly...)

 

Bore/ring wear is more likely and accounts for both symptoms. I have heard that running really rich can lead to the oil film on the cylinder walls breaking down and increase wear of the bore and rings (see "cylinder glaze"), but I don't know if this is only during break-in.

Edited by Mr Dave, 23 April 2015 - 12:28 PM.

[Lytesben]

It has done 58,000 miles I believe and unfortunately I don't really know how low the compression was.

 

So it sounds like I have bore/ring wear then? I'm guessing that is an engine rebuild job? What's a rough sort of price for that to be done? I was hoping it was just going to be head gasket and be nice and simple but nothing ever is! 

[gazza82]

Previous owner may not have been adding lead-additive so running on unleaded may have damaged the valves/valves seats.

 

If the head gasket has gone you won't see from the outside .. but the signs will be on the spark plugs ..

 

There's really only one way to find out for sure ...

[DomCr250]

If it's been running very lean it could be valves - I've seen a few exhaust valves cracked and burnt over the years?

 

Can you ask or borrow a compression gauge ...then try a quick test ... if you test as is then pop a small amount of oil down the bores and try again it may help you decide if it's valves or worn bores / piston / rings ...much easier than pulling the head off.  The compression will improve if it's worn bores but will not if's it's valves.

[Lytesben]

Previous owner may not have been adding lead-additive so running on unleaded may have damaged the valves/valves seats.

 

If the head gasket has gone you won't see from the outside .. but the signs will be on the spark plugs ..

 

There's really only one way to find out for sure ...

 

What sort of signs would I be seeing on the spark plugs? They have only recently been changed so would they show signs so soon? 

 

I think I am going to need to get the head off this weekend and see what I can find.

 

If it's been running very lean it could be valves - I've seen a few exhaust valves cracked and burnt over the years?

 

Can you ask or borrow a compression gauge ...then try a quick test ... if you test as is then pop a small amount of oil down the bores and try again it may help you decide if it's valves or worn bores / piston / rings ...much easier than pulling the head off.  The compression will improve if it's worn bores but will not if's it's valves.

 

It hasn't been running lean, but really rich. 

 

I did have a compression gauge but typically cannot find it now. Might have to go and get one at the weekend and try that. I was just reading the haynes manual and saw that exact same test so worth giving it a go and then maybe taking the head off to have a proper look.

[Steve220]

Piston rings. Oil is getting past the control ring and dumping it into the cylinder. This is what is causing the blue smoke.

Low compression = low air to fuel ratio = inefficient burn as too much fuel per unit air, therefore runs rich.

Rebuild or new engine.

Edited by Steve220, 23 April 2015 - 04:08 PM.

[Broomer]

Where abouts in Somerset. Your more than welcome to borrow my compression tester

[Fast Ivan]

get a leak down test done and check the valve clearances yourself

[KernowCooper]

Before I pull anything apart I'd do the compression test and this will give you a better indication, rather than pull the head and do whats visible and replace it to find it was time and money waisted and having to find out the issue a second time

[carbon]

Blue smoke, seen a lot worse...

 

And before taking the engine apart do you know roughly how much oil you're getting through (miles per pint?).

[KernowCooper]

Blue smoke, seen a lot worse...

 

And before taking the engine apart do you know roughly how much oil you're getting through (miles per pint?).

Me too I was expecting lots more blue smoke

[ChopperHarris]

do the comp check, add oil in the bore to determine bore or piston wear....grandmother/eggs?

[Lytesben]

Blue smoke, seen a lot worse...

 

And before taking the engine apart do you know roughly how much oil you're getting through (miles per pint?).

 

 

 

Blue smoke, seen a lot worse...

 

And before taking the engine apart do you know roughly how much oil you're getting through (miles per pint?).

Me too I was expecting lots more blue smoke

 

 

Believe me when it is first started when I drove it back from the garage there was massive clouds coming out of the back, so much that I couldn't really see behind me. It appears when it has been run for a little while there isn't so much at all. 

 

do the comp check, add oil in the bore to determine bore or piston wear....grandmother/eggs?

 

Ha I will definitely do the compression check. 

 

I might be able to get hold of a Metro 998 engine with low miles for a couple of hundred quid - I believe that these can basically be dropped straight if you use the Mini engine mounts and change the thermostat housing?