6 replies to this topic

[TheHunterHofman]

Hi all,

 

As the title suggests, I wonder if I have a head gasket failure on my 2000 Mini Cooper MPi. So I did a (cold) compression test the other day and the results were quite consistent: 195 psi, 185 psi, 195 psi and 180 psi, so on the basis thereof, I didn't suspect a head gasket failure (but maybe that's naïve).

 

When the car warms up, it eventually starts to boil the water in the coolant system, and smoke (exhaust gasses?) erupts from it (when having the cap off). I then tried a CO2 tester, and the mixture turned from blue to yellow (indicating that there is a failure of the cylinder head or head gasket). Having said that, the oil looks to be squeaky clean, the thermostat is renewed and the car has a new waterpump.

Here's a bit more detail of what's going on with the coolant system: https://youtu.be/ocZLkOCwkMk

 

I did note that one of the four spark plugs' electrodes was a bit blacker than the other three, not sure if that's an indication of a failed head gasket, but would love to hear your thoughts on this.

 

Apologies for me not being an expert on this (yet), but thought I'd ask here first before disassembling my engine.

 

Thank you,

[cal844]

The coolant test alone tells you that it's failed to coolant passage, best to remove the head and check it

[Lplus]

Looks to me like the start of headgasket failure - especially the gas test.  Leakage from cylinder to water passage only when hot is a thing.  I've had that on three engines I've known  (not A series, but whatever), they tighten up when cold.  Might be worth checking head nut tightness, but even if they nip up a bit the leak path will have been established.   If you run the engine for a while and let it go cold, is there still significant pressure in the system?

 

And the smoke from the rad could be a weep which only appeared when you put the system under pressure - did it dry out?

 

I didn't realise the heater knob on an MPI is the wrong way round - earlier minis have push in for heat.

[TheHunterHofman]

The coolant test alone tells you that it's failed to coolant passage, best to remove the head and check it

 

Sorry, don't quite get that: failed to coolant passage? Will remove head anyhow, have ordered a new head gasket (Payen BK450).

 

Looks to me like the start of headgasket failure - especially the gas test.  Leakage from cylinder to water passage only when hot is a thing.  I've had that on three engines I've known  (not A series, but whatever), they tighten up when cold.  Might be worth checking head nut tightness, but even if they nip up a bit the leak path will have been established.   If you run the engine for a while and let it go cold, is there still significant pressure in the system?

 

And the smoke from the rad could be a weep which only appeared when you put the system under pressure - did it dry out?

 

I didn't realise the heater knob on an MPI is the wrong way round - earlier minis have push in for heat.

 

Haven't checked if it still holds pressure after letting it go cold, it does hold some pressure when the engine is turned off for about 10 minutes though. I have checked the radiator for leaks, and there appear to be none, so not too worried about that puff of smoke coming from it (as you've seen in the video).

 

I have now ordered a head gasket (Payen BK450), when installing I'll make sure I tighten everything down in the correct way.

[timmy850]

There is likely a leak from one of the cylinders into a coolant passage. 

 

This can happen when the head gasket fails between a cylinder and coolant passage. It won't always fail between oil and coolant

 

Another possibility is a crack in the head casting somewhere which is allowing combustion pressure into the coolant

[TheHunterHofman]

There is likely a leak from one of the cylinders into a coolant passage. 

 

This can happen when the head gasket fails between a cylinder and coolant passage. It won't always fail between oil and coolant

 

Another possibility is a crack in the head casting somewhere which is allowing combustion pressure into the coolant

 

Alright, clear. Would that perhaps explain the slightly lesser compression on one of the cylinders, and the slightly darker electrode of one of the spark plugs? Can't remember if they concerned the same cylinder, but seems plausible now.

[Tones61]

There is likely a leak from one of the cylinders into a coolant passage. 
 
This can happen when the head gasket fails between a cylinder and coolant passage. It won't always fail between oil and coolant
 
Another possibility is a crack in the head casting somewhere which is allowing combustion pressure into the coolant

 
Alright, clear. Would that perhaps explain the slightly lesser compression on one of the cylinders, and the slightly darker electrode of one of the spark plugs? Can't remember if they concerned the same cylinder, but seems plausible now.

When you remove the head,you may see some steam cleaned piston marks too,
And the fire ring failure:-)