Headgasket failure analysis N/A 1380
Turbo Mini Forums

I was driving along yesterday steadily through the village and noticed the car running rough, sounded like an exhaust blow, I then realized it wasn't so parked up and got towed all of 1.5miles home (Glad I didn't try to make it home now.)

Thinking it sounded like a carb issue I inspected that but it seemed fine, so whipped out the compression tester and sure enough cylinders 2 and 3 were dead.

The first thing that struck me was the light colour of the spark plugs, as illustrated by the combustion chamber colors.

I'm wondering whether it has gone lean and lightly toasted it as I heard the fuel pump sucking fuel about 12 miles before the actual faliure, upon some hard cornering, so took it easy to allow the fuel to flow through again, even so the engine did not miss or cough. It had had a kicking about 5 miles before it failed after filling up with fuel. (Tesco 99 octane) When it failed I had been taking it easy for a good 3 miles.

What are peoples verdict on these photos. The middle two piston crowns have some hard carbon deposits almost like welding splatter. If that is of any use for identifying the failure who knows.

I have shown photos of cylinder 1 and 2 to show the difference in colour. Usually they are not so abruptly different.


On the plus side I have had the opportunity to decide where to slot a gt17 down the back with the 16v head should I so decide to go down that route, and replace my crappy old manifold with a new one.

Cylinder number 1



Cylinder number 2

Edited by minimole23 on 25th Jun, 2012.

Ill put money on the Tesco fuel being the culprit

I seriously doubt it!

I doubt its the petrol. The octane rating is pretty strictly controlled and I don't think the lack of additives others may use in premium fuels would make enough difference to kill the gasket. Certainly not if 97 octane is ok normally. I think the clue is in hearing the fuel pump sucking is a good pointer, it's been starved and gone lean enough to cause a problem.

I will be fitting my fuel swirl pot as soon as I get it cut down, and re-welded.

Here are the spark plugs.

i am far from an expert but the plugs look like the engine has been running leaner than i would run personaly

Yes i moved to the darkside

Instagram @jdm_brett

I agree, brown for cruise, black for power.

Unless those plugs were removed after shutting the engine down immediately after the blow, they bare no relevance whatsoever to how it was running at the time.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

From the head it looks like it has been running generally lean. The damage to the gasket is definately pinking/det damage.

A bit richer or a degree less advance may help.

If you have a carb, then don't waste your money on a swirl pot, the carb already has a resevoir (float bowl) for just this purpose.

Ultimately, how long has the gasket been on? they don't always last forever.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Tesco 99 is nowhere near 99 I have been reliably informed. It does look like its been running lean but I still think its the Tesco fuel - especially since Tesco do not allow their own fuel to be put in their own vehicles

I seriously doubt it!

The gasket has covered about 1000 miles

100 miles flat out at castle combe, and the rest has been road use and drag racing.

I would say I have this sussed now, the more I think about it.

There is too much ignition advance or not enough fuel going through at about 3k rpm, when hardly touching the throttle. what to me seemed like a miss/camminess/general hot cammed 1380 ness actually was a bit of det, and that has toasted the gasket. hence it failing when taking it easy down hill into the village, not when spanking it up zig zag hill.

I'll get it running, check the advance and get it too a rolling road I think to double check it.

Edited by minimole23 on 26th Jun, 2012.

I have heard that the MON is low for the Tesco99 stuff.

The Tesco's near me Is ESSO garage :) there fuels fine. but big tesco's just says tesco so no idea's who's fuel that is

Bk450 head gasket and shell fuel and ul be away again

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

we all learn from mistakes

13.95 1/4 mile on a 2.95 fd. Carnt be that hard to beat!

Well new gasket on, faces cleaned, all torqued down properly, tdc double checked to make sure the ignition is set properly.

Just need a trip to maniflow to get new centre section for my exhaust as I reckon thats costing me a couple of horse power at the top end.

We shall be back faster and hopefully more reliable!

Did you re-torque it after a few hundred miles last time?

Edited by BENROSS on 27th Jun, 2012.