KV6 190 persistent overheating

[mgb66]

Arctic, many thanks for this. The O-rings were certainly flattened and I've replaced them with R-18s from my spares. Trust that's the right size.
Presumably this could partly explain some loss of coolant.
Regarding the re-fill procedure the Haynes procedure suggests removing the expansion tank bleed hose from the top of radiator.
In other descriptions of the procedure this is not included. Is this important?
I can see though that being at the top of the system it is a place for trapped air to escape from.

However once the expansion tank is raised up it is one of the first places for coolant to escape whilst refilling.
Also regarding coolant level the Haynes procedure specifies filling the tank to just below the filler neck. However as soon as the engine is started as per the procedure coolant overflows.
Is this anyone else's experience?
Oh, what fun this all is. I'm so looking forward to possibly having to change the thermostat.

[stevestrat]

Originally Posted by mgb66

Also regarding coolant level the Haynes procedure specifies filling the tank to just below the filler neck. However as soon as the engine is started as per the procedure coolant overflows.
Is this anyone else's experience?

Haynes are ok but there are inaccuracies, just below the filler neck is way too high, doesn't allow any room for expansion once the water heats. As you can see from the photos posted by myself and Arctic the MAX coolant level is at the bottom of the tank. Syphon your own tank and you'll see the markings for yourself. If you overfill the tank the excess coolant will be expelled.

Another boo boo in Haynes is that the brake fluid reservoir doubles as the clutch reservoir . . . . utter bolox! The clutch fluid reservoir is on the master cylinder at the top of the clutch pedal.

[mgb66]

Steve, thanks for your post.
Having replaced the O rings on the cap I re-filled the system and ran the the car on fast idle as specified. Straightaway the coolant level rose, and as it did so I syringed out approx 700ml before the fan cut in and I replaced the cap, then switched off the engine.

I will let it cool completely and then re-check the level.
This is not quite as the book but that method has definitely not worked so far and I suspect that the combination of overfilling and the flattened O rings has cost me about £60 in OAT mixture.
Fingers crossed.

I must say I'm very grateful for the moral support this forum gives you in trying to keep these older but well liked MG Rovers going.
Thanks again,

Peter

[stevestrat]

Originally Posted by mgb66

I must say I'm very grateful for the moral support this forum gives you in trying to keep these older but well liked MG Rovers going.
Thanks again,

Peter

That's what the club is all about Peter, we all started out the same, asking questions and no matter how "simple" the question might seem what you'll never get is a response saying "that's a stupid question!". Wait til you get the sense of achievement from being able to offer advice rather than asking for it.

[SD1too]

Originally Posted by stevestrat

Haynes are ok but there are inaccuracies, just below the filler neck is way too high ...

Just to avoid confusion, the procedure in Haynes which Peter is following is for the initial refilling and bleeding of the cooling system. For that, it is correct to fill the expansion tank to the filler neck. When the engine is started, the level will drop and more coolant will need to be added. As Steve points out the final level, after bleeding, should be no higher than the 'Max' marker.

The small diameter bleed hose at the filler neck should not be removed. It is the clip holding it to the radiator top hose which needs to be released so that there is sufficient slack to raise the expansion tank to high level.

Simon

PS There are also errors in RAVE.

[kaiser]

Originally Posted by SD1too

Just to avoid confusion, the procedure in Haynes which Peter is following is for the initial refilling and bleeding of the cooling system. For that, it is correct to fill the expansion tank to the filler neck. When the engine is started, the level will drop and more coolant will need to be added. As Steve points out the final level, after bleeding, should be no higher than the 'Max' marker.

The small diameter bleed hose at the filler neck should not be removed. It is the clip holding it to the radiator top hose which needs to be released so that there is sufficient slack to raise the expansion tank to high level.

Simon

PS There are also errors in RAVE.

If the expansion bottle is filled above capacity, the excess will just be ejected. So you can fill to your hearts content, the optimal level will automatically be found, if you have enough in the system.

[mgb66]

Thanks again all for your posts on this.
If I try to quickly summarise what has happened over the past few days with my attempts to refill the cooling system, I would be very grateful for your opinions on what the fundamental issue might be.
Yesterday after some discussion with Simon I jacked the car up, removed the undertray and drained the system via the bottom radiator hose and the engine drain plug.
I then flushed the radiator through with a hose, following with the engine as best I could, given that the thermostat was still in place.

I replaced the the radiator hoses and engine plug and refilled the system as per Haynes, but with no overfilling to the expansion tank neck as previously, since experience over the past few days tells me that would be an immediate issue once the engine was started.
Having secured the expansion tank back in place I set the IPK Diagnostics to indicate temperature and started the car.
As in the previous three attempts the coolant level in the expansion tank went from the MAX mark to overflowing almost immediately which I countered by syringing out 20ml at a time, until eventually I removed 650ml which has been typical of previous attempts to refill the system.
Eventually the level stabilised and I replaced the expansion tank cap. (Now fitted with new O rings, not exactly the correct size but certainly sealing adequately.)

Whilst trying to keep the revs as per the Haynes procedure I was also trying to keep an eye on the temperature which was rising until the fan cut in at 103. I left it running for less than a minute by which time coolant was flooding out of the expansion tank.
I switched the engine off.
There must be a conclusion from this series of events.
Given the continual rise of temperature it would seem that the cooling system is not functioning at all. The thermostat could be stuck shut or an airlock is preventing circulation.

The rapid return of coolant to the expansion tank before the liquid is even warm would suggest its being forced out by an increase in pressure.
If an airlock is the issue then I will have to employ another method of refilling the system as I have now gone through the recommended procedure four times (though only once starting with a drained system).
The history of overheating with this car which has happened at least four times over the last three years is that after an ENGINE OVERHEAT warning, inspection of the expansion tank shows the level has dropped below MIN, and to get it back to the MAX mark at least 750ml of coolant was required.
The gradual loss of coolant between these incidences may have been a poorly sealing pressure cap and lack of attention from me with more frequent checks.
The rapid rise in level of the coolant in the expansion tank would suggest to me that the system is being pressurised, possibly from the failure of a head gasket.
There are no other obvious indicators for this as in oil contamination but I cannot see any other explanation.
I would dearly love this not to be the case as, perhaps foolishly, this ZT-T is my everyday car, and much as I enjoy driving it, sadly I think would have to consider major repairs of the engine an unrealistic proposition both in terms of time and money.
Peter

[kaiser]

You have a headgasket problem or a crack.
That much is almost certain.
Repair of the engine is not as expensive as you might think, in parts, at least


I am about to repair mine!
Smoke out the exhaust, Water!

[dave lincs]

Originally Posted by mgb66

Simon, thanks for your interest. I'm in SW18.
Peter

Hi Peter
Try bypassing the oil cooler this will stop the coolant flow if blocked

Dave

[T-Cut]

Originally Posted by mgb66

As in the previous three attempts the coolant level in the expansion tank went from the MAX mark to overflowing almost immediately

There's your clue. A cold system wouldn't do that without exhaust gas getting in, no matter how full it was.


TC