KV6 overheating and losing coolant

[ricebridge]

Hi everyone!
My 2002 ZT-T, which I just bought, tends to suddenly shoot its temp gauge to max and warn of engine overheating. It seems to be losing coolant as well. Or does it?
Having read through some similar problems here on the forum, I understand it’s not uncommon with these engines. Then again, I’m worrying about HGF and would be grateful for any advice or help.

So let me explain the symptoms in detail:

I drove it home on a 1,000+ km trip from where I bought it, with plenty of motorway driving. During this trip, I must have put in at least 4 litres of coolant. Is 0.04 ml per km a lot? And where did it all go?

I first thought it must be a faulty sensor somewhere. Or could it be the thermostat? According to the service history, it was replaced only some 3,000 kms ago. Good or bad?

The heater seems to put out most of the heat around my feet. That would mean an air lock, wouldn’t it?

I just drained the system and replaced the coolant, being careful to bleed it all just the way Uncle Haynes tells me to. But the problem is still there. Or, at least it was during my test drive late last night. The expansion tank was half full (or half empty, for those so inclined ) — if the coolant is escaping somewhere, how come the tank, which is at the highest level, still contains coolant? (Last time I looked, fluids ran downwards...) This was the first time I did it on any MGR. Did I get it wrong after all, and create a new air lock?

I checked the engine oil, although I did not loosen the drain plug and take a larger sample. But around the dipstick it was perfectly fine, and when I stuck my finger inside the engine at the filler hole after removing the filler cap, the oil I could touch there was just as good.

On the inside of the filler cap, however, there was indeed some ”mustard” (yellowish sludge), perhaps half a teaspoon of the stuff, absolutely no more. That set the HGF alarm bells off in my wallet, but then again, I understand that there could be other reasons for such stuff to build up over time (clasping at straws here...) And shouldn’t there be more, and shouldn’t there be sludge elsewhere too, in case of a HGF?

I’ve checked all over the engine for coolant residue, but the results were inconclusive. However, I did notice that one copperish-looking pipe (bear with me pls for not knowing all the exact technical terms here) that goes across the engine below it at the front, and which is connected to the hose leading down from the expansion tank, was greenish. Is that even an original part? Why put a piece of copper pipe into a hose-based cooling system? Won’t that cause corrosion from aluminium parts?

There’s no misfiring, and I can see no white smoke from the tailpipe when driving, although I do tend to sit at the front of the car when driving, so visibility of the exhaust is somewhat limited...

Grateful for any help or comment!

[Brunty]

The expansion tank should not be half full, the max level is visible when the tank is nearly empty. Could be that you are overfilling it and it is being pushed out through the expansion tank cap. I did the same when I got my first Rover 75, convinced that I had HGF, even though there was no sign of mayo in the oil. Let it settle down to max on tank, then see what happens.

[ricebridge]

Originally Posted by Brunty

The expansion tank should not be half full, the max level is visible when the tank is nearly empty. Could be that you are overfilling it and it is being pushed out through the expansion tank cap. I did the same when I got my first Rover 75, convinced that I had HGF, even though there was no sign of mayo in the oil. Let it settle down to max on tank, then see what happens.

That’s certainly a thought. I understand that the caps tend to leak after a few years?
There’s certainly a leak somewhere. I noticed now when driving through town that I left quite a trace.

[T-Cut]

Originally Posted by ricebridge

There’s certainly a leak somewhere. I noticed now when driving through town that I left quite a trace.

You mean there's a trail of water on the road?
If that's coolant, then it would explain the 4 litre/1000km consumption. In good condition, the cooling system doesn't lose any coolant.

Don't fill the header tank above the MAX marker. Look down the filler neck to see MIN/MAX at the bottom. When full and cold, the level should be like this:



- just level with bottom of the ribs.

Have you checked for coolant pooling in the V between the heads?

This is the most common area of leakage and stems from the thermostat housing also located between the heads. Remove the engine cover to check.

Does the radiator fan operate as it should?
Do the Demist Test to check.

Find the normal running temperature by invoking the Trip Screen Diagnostic Mode
How To:https://www.the75andztclub.co.uk/for...agnostics+mode
It should run at around 90C. The temperature gauge tells you almost nothing of any use.

TC

[ricebridge]

Originally Posted by T-Cut

You mean there's a trail of water on the road?
If that's coolant, then it would explain the 4 litre/1000km consumption. In good condition, the cooling system doesn't lose any coolant.

Don't fill the header tank above the MAX marker. Look down the filler neck to see MIN/MAX at the bottom. When full and cold, the level should be like this:



- just level with bottom of the ribs.

Have you checked for coolant pooling in the V between the heads?

This is the most common area of leakage and stems from the thermostat housing also located between the heads. Remove the engine cover to check.

Does the radiator fan operate as it should?
Do the Demist Test to check.

Find the normal running temperature by invoking the Trip Screen Diagnostic Mode
How To:https://www.the75andztclub.co.uk/for...agnostics+mode
It should run at around 90C. The temperature gauge tells you almost nothing of any use.

TC

Thanks, I took it on an extended trip checking it with the diagnostics now. As long as I’m coasting along on a level road, not exceeding 3,000 revs, the engine temp stays between about 90C and 107C; the engine fan kicks in at about 102C and keeps it all in check. However, as soon as I put the engine under any kind of stress, such as revving it up a bit or going up a steep hill, the temperature shoots up. It peaked at about 133C which sounds a lot to the untrained me.
Ambient temperature was between +5 and +6C.

[T-Cut]

Well that raises all sorts of thoughts doesn't it?
Certainly raising to 130C isn't good for the head gaskets.

EDIT: I've deleted several technical questions.
My advice is to not drive the car until you can get someone in the know to examine it. If it doesn't already have HGF, it will if you continue as above.

TC

[Randyjim]

Originally Posted by ricebridge

However, I did notice that one copperish-looking pipe (bear with me pls for not knowing all the exact technical terms here) that goes across the engine below it at the front, and which is connected to the hose leading down from the expansion tank, was greenish. Is that even an original part? Why put a piece of copper pipe into a hose-based cooling system? Won’t that cause corrosion from aluminium parts?

It seems like at some point the rigid steel pipes to the oil cooler have been replaced with a homemade copper set. These are prone to corrosion, and the stainless steel sets are quite expensive, so using copper can save money.

With regard to the overheating, is the radiator getting hot? You have very high temperatures at 133C. This could be reached quite quickly in the engine block and cylinder head if there's a circulation problem. This could be due to an air lock, a failed closed thermostat or a failed water pump or another blockage of some sort.

[SD1too]

Thanks for testing the fan Jonathan. Jim makes a very good point:

Originally Posted by Randyjim

... is the radiator getting hot? You have very high temperatures at 133C.

Warm up the engine until the radiator fan starts running. Open the bonnet and locate the bottom radiator hose. It's the large diameter hose with the bleed screw in it, alongside the battery box. Is it uncomfortably hot to touch? What's its temperature compared with the radiator top hose?

Originally Posted by ricebridge

BTW, an independent mechanic suggested it might be the water pump, since there is no visible motion in the water in the expansion tank. Any thoughts on that?

The coolant circuit doesn't flow through the expansion tank so that observation is irrelevant. Also, water pumps usually give trouble by leakage. It's rare for the impeller to become detached from its spindle so that possibility is not a good bet.

Can you report back on the hose temperature please Jonathan? Oh, and don't let it get to 133 degrees will you.

Simon

[ricebridge]

Quick hose check without a thermometer shows them both to be equally hot. Not scalding, though; more like a nice cup of tea. Was that good or bad?

[SD1too]

Originally Posted by ricebridge

Quick hose check .... shows them both to be equally hot ... Was that good or bad?

Good in that there is flow through the radiator so your thermostat must be opening, but bad in that we're no further forward!

Time to find out where that trail of water is coming from (which you mentioned in an earlier post). You've checked in the 'V' haven't you?

Simon