Head Gasket failure!? My Ka Mk1 project....

[dishman]

Well, this was an unexpected event in my ford ka mk1 maintenance journey.

It looks like the head gasket has failed.

The car had been on a long journey. Although when the event happened, it was the following day after a 15 minute run, and the coolant temp light came on. Hopper was near empty. No sign of fluid in the oil, no mayo.

Fluid was added, and the car ran fine back to a safe place, no further sign of coolant loss.

At first I was hoping it was the heater control valve, but there was no sign of actual leak after running the car. There was some evidence of boiler over, but only very slight (a few tiny drops of red coolant near the hopper, but no large soaked area).

The RAC came out to investigate and did a exhaust gas check and reported there is a very slight colour change.

They then surmised that it seemed like the thermostat was not opening.
So, It looked liked the thermostat failed initially and then the engine cooked, even though the car was stopped quickly.

People may remember i did a major flush of this car's coolant system and replaced the thermostat 2 years ago. So, I’m a bit miffed the thermostat failed. I documented it here.

https://www.diynot.com/diy/threads/ford-ka-mk1-coolent-flush-query-and-questions.632020/page-2

Could that heavily lime-scaled coolant that sat in the engine for years beforehand have done more damage than i realised?

Apparently there is an issue with the thermostat housing (failing seal?) and a trapped air pocket that can cause thermostat failure like symptoms. (Need to check if this is true)

So, prognosis..... head skim and a new gasket? Like i said, no signs of mayo yet.

Thoughts on where to go next, much appreciated.

 

[Burnerman]

Real bad luck, that one!
Let's not jump in too soon, remove and test the thermostat once more, then fill up with coolant and start up. You'll feel a surge of heat when the thermostat opens if you hold your hand on the radiator. Then, look for bubbles and maybe some oil in the header tank. If your engine has the iron head, a skim isn't usually needed!
Regards
John

 

[dishman]

This is the 1.3 duratec, so cast iron block and aluminium head I think.

Thermostat was not opening when the RAC guy ran the car (i was not there in person).

There is a potential known thermostat housing issue with this car where an air bubble can form there caused by a potential micro crack in the thermostat housing. This could have prevented the working thermostat from firing.

The coolant temp sensor is in this location so I could remove it to see if any air escapes.

Then, look for bubbles and maybe some oil in the header tank.

Are you saying that oil may not show in the header tank until the thermostat has opened up all the way and let coolant circulate via the radiator?

 

[Gasguru]

Your could buy a combustion leak tester that fits the expansion vessel...the test liquid changes colour in the presence of combustion products.

 

[dishman]

See my op ^. The RAC guy did that and said there was a very slight colour change detected. It sounded like it was a very weak colour change, but a colour change non the less. It did not go bright green or yellow. (I was not there to see this in person).

The person who was there said they could not actually see a noticeable change from blue. But that is obviously someone without any experience in assessing the expected colour change.

Would getting a follow-up of compression tests, Pressure test and a leak-down test be the next best course of action?

 

[Burnerman]

A compression test would (probably) only show a leak between the combustion chamber(s) through the gasket - not necessarily into the waterways.
I've used the colour test kit before - it was conclusive on a major failure but a lot less so otherwise.
I can't say if the alloy Duratec head can be skimmed - not all alloy heads can so you can investigate further before considering head removal so I'd replace the thermostat with a genuine item, bleed all coolant air out as you can, run the engine up to temperature with the heater on and see how you go.
Fingers crossed for you!
Regards
John