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

[dishman]

Ok, interesting development....

Head Gasket test seemed to show no combustion gas.

Engine was up to temperature, I could see a regular slow air bubble as the engine ticked over pass through the tube, through the blue liquid, and it did not change.

I then realised the heater and fan were not on full for full circulation and when I turned that on, even the air bubble stopped and there was seemingly no gas escaping. The colour stayed blue. I even added a little squeezer to the tube and pulled air through the fluid and still no change.

There were two instances where the fluid went green, but I put this down to user error. I let the car heat up too much and the coolant had expanded to the top of the tank and it interacted with the tube. The second, again the engine was too hot and steam made it's way into the test tube and seemingly contaminated it.

So I am pretty sure I can exclude those two attempts.

So......I am pretty certain the head gasket is ok........I think.


But.....the initial overheating cause is still a problem it seems. Not a one off......

The car was taken on a long drive, and it did not overheat. In fact, it was difficult to get it hot enough to make the fan come on. It stayed in the early 90s and rarely went higher.

Then after finishing the drive I turned the engine off. The temperature rose at this point to around 102 and it was enough to make the fan activate.

So we can exclude fan failure.

However at this point something went amiss.

I went to check the coolant level and it had lost about 500ml, it was low on the coolant vessel.
But again, no indication of where it leaked from.

So either there was a coolant leak whilst driving, either a sudden release due to pressure or something else.

I can't see a drip or leak whilst the engine is idling.

Any ideas where to explore next? Pressure cap, thermostat micro leak and water pump?

A cold pressure test of the coolant system?

Edit: Now leaning water pump failing.

1. It has not been replaced in 18 years
2. I have always noticed it being slightly damp in plastic bumper undertray near the water pump. While there is no evidence of red fluid, it has always struck me at odd it always seemed to be damp near here. I always put it down to rain water draining to this point, but the water pump is just above it. So i am thinking there has been a slow leak for a while (hence the very slow but noticeable coolant loss), and now it has accelerated.

 

[Burnerman]

Does your car have a plastic under tray that you can remove completely for a while? So long as the roads are dry, there shouldn't be any dampness there.
If so, take it off and see if anything is visible there.......all plastic parts are prone to failure, and the water pump is also a suspect - but you'll need to remove the belt covers from this. Surely there will be colour traces somewhere.....!
One other thing......check the carpets inside below the heater unit for any dampness.
At this sort of age, I'd also say the radiator could be on borrowed time......look for damage where the core joins the bottom tank.
John

 

[dishman]

There is not a total engine under-tray, it's more of a bumper under-tray, which forms a kind of collecting area. The side I notice the water collecting on sometimes is near the water pump housing, but also the radiator.

I'll see what happens after the next downpour (as i ensured it was dry). If it gets wet, I know rain is at least one certain cause.

Today I did a more aggressive idle test. holding more revs, trying to replicate getting it very hot and shutting off it off at peak temp.

This time it got it hot enough for the fan to activate a few times. It never went above 102c.

I monitored the expansion cap, had a good view of the water pump, radiator and thermostat housing. I even put paper towels near those areas to try and clearly catch any drips. Nothing at all.

So my next guesses are:

1. It is something that only presents when the engine is under more load at higher rpm.
2. That there is no issue and the most recent coolant loss was it settling and just dropping, as it was it's first hard run since the initial breakdown.
2a) this would mean the first coolant loss had to be a one off. (which would be unlikely maybe?)

3.I had a really good look for red stains or anything to indicate coolant being dumped at high temp. But I can barely see anything. No clean spots or marks on the bonnet underside. Nothing that looks like something has sprayed the interior with red hot fluid. I can see some very vague redness in the area around the water pump. But it is very hard to tell if this is the remnants of fluid or just dirt or something.

I guess my next options are to try another test drive and replicate what happened last time, or an actual coolant system pressure test?

 

[Burnerman]

Sadly, we're in the realms of guesswork here!
I don't think a coolant pressure test would show anything......if there was an issue here it would have shown up by now.
There's a significant difference in running the engine up to water temperature whereas a good hard run would elevate the engine block temperature somewhat higher - if you get my drift.
I think the only thing you can do is to monitor the situation very carefully, especially the coolant level which shouldn't change at all......even for your first time.
Ford engines are pretty good at self bleeding, and there shouldn't be any bubbling visible at all after a mile or two. Please look at the expansion bottle here.

Back in the days of yore, I used to work on Hillman Imp competition engines......all alloy, they were. (Clan Crusader). In normal road use they were pretty stable, but when used in competition they did often fail - due to porous aluminium castings and dubious cooling systems.

Are you happy with the radiator condition?
John

 

[dishman]

Are you happy with the radiator condition?

Radiator looks in good condition. No signs of weeping or anything. And with that bumper trey underneath it, I would expect it to capture some evidence of red liquid.

(Also rain water was pooling in that tray this morning, so I can exclude that).

My guess at the moment is still the water pump. Apparently one failure mode they can exhibit is where it only drips/leaks under load, once the engine is warm and over a certain rpm.

I was always imagining a sudden release of coolant and lots of splashing, but I have realised it could be just an accelerated drip that just increases over a certain threshold (maybe exponentially as revs rise). This would explain why there is no evidence for it. It just drips onto the road, but only while driving.

It also fits the original coolant loss incident. It could have been slowly leaking on the long journey and finally got too low a few days later.

It could also explain the very slow coolant loss over time I have noticed (a few cm every 6 months). It could be that the issue has just got worse.

So that could be it...

I either go for a water pump replacement without direct evidence.

Or I fashion some sort of makeshift under-tray to try and capture evidence of drips whilst driving.

 

[Old Salt]

If your getting drips whilst driving it will smear across the various surfaces or be dripping whilst stationary after a run.

If it was my car I would drain the coolant, back flush the block and radiator, change the thermostat and possibly the water pump depending on cost.

Triumph stags can be a bugger to bleed so I used to get the front jacked up high and then run the engine with the expansion cap/ rad cap off until bubbles ceased.

Make sure the heater is on full whilst flushing and bleeding. If you still have air in the system try disconnecting the heater return until a good flow is established.