HELP! Freeander Coolant Loss Mystery...

Hi

I have a 1998 Freelander XEDi 1.9L "L" series diesel. See photo. Love it to bits...

...(there's always a "but")...

...but I've got a mysterious problem at the mo, which I'd appreciate some help with.

Ever since I got it (Sept 2008), it's lost a bit of coolant. Previous owner had mentioned this. It has required about 0.25-0.5 litre of coolant top-up every week (approx 250-300 miles). The loss apears to come from the reservior bottle/expansion tank. NB: there is no white smoke from the exhaust (in fact there is no black smoke either...long may both continue!). The leak definitely seems to come from the expansion tank only. I tried changing the cap, then I changed the expansion tank itself a few weeks ago as it appeared to have stress fractures around the cap area. The new tank is an upgrade as they have changed the design. It now has a bigger diameter cap & the latter has a mechanism so you can't overtighten it (it clicks & turns around in your hand when it is on tight enough).

In all this time the engine temp gauge has never gone above halfway. I know it needs topping up because the fan comes on a lot. So I've just lived with it.

Today, things changed dramatically for the worse.

I noticed a loss of power, glanced at the temp gauge & it was in the red! I was on a 20 mile round trip & I had to complete it fast (son's karate grading). I kept filling the expansion tank (including bleeding the system via the heater matrix bleed screw) & in those 20 miles I had to top the system up 5 times. Took over 10 litres of coolant refills to get me home. Journey from hell!

The escaping coolant comes from under the expansion tank cap. This is clear. You can see it boiling up inside the expansion tank & the pressure deforms the expnsion tank bottle so much that the cap is skewed & pushed upwards on one side & the boiling coolant escapes as steam & boiling liquid. It appears as if the engine is getting really hot despite the coolant & the fan working more than it should.

So, what on earth's happening? Is it something to do with the thermostat? Or does anyone know of some other cause?

If it's the thermostat, is it a big job to fix it?

Many thanks.

Jack

It could be the thermostat but as its been using/loosing/pressurising coolant for some time without any temperature rise it's more likely to be the head gasket.

Thanks, Chaser.

The basic problem is that the coolant is getting so hot that it is boiling. This is building pressure & heat and the expansion tank is deforming as a result. This twists & pushes the cap up & that's where the coolant loss occurs. I know this 'cos I saw it happening yesterday. If it were the head gasket, there would be white smoke from my exhaust wouldn't there? Anyway, even if the HG were iffy, I know that the main loss is via the expansion tank.

Thinking about this overnight, I think it is probably one of or a combination of the following: knackered thermostat (staying shut so coolant is not going via the radiator therefore it overheats), an air lock(s), or some blocked coolant pathway (perhaps in the radiator, making it inefficient). I'm assuming the coolant pump is OK as coolant seems to go back into the expansion tank... although I could do with someone else's advice on that.

So, initial plan of action: renew thermostat and flush engine & radiator (independently). See what happens then.

Oh, and just to correct the "deliberate" mistake, it's a 2.0 litre "L" series engine of course, not a 1.9L. I also run a 1.9L diesel Punto for my daughter to use & got mixed up.

Thanks.

Jack

There's no harm in trying the thermostat first. L series head gaskets aren't noted for failure.

The reason that I say it may be the head gasket is because it's difficult to say whether what you think is boiling due to no circulation is actually hot combustion gasses pressurising the system.


Either way the coolant loss will be from the expansion tank pressure relief valve so that doesn't really help diagnosis.

Testing the coolant for the presence of combustion gasses would confirm.
The white smoke thing is not a necessary symptom of head gasket failure.

Lets hope it's the cheaper option.....

Ah. I see. Thank you, Chaser. Yes, that sounds logical.

I've been talking to a local (& down to earth) independent LR garage. They recommend that the radiator is checked for free flow through as a starter for ten, then look at free flow through engine, then look at the thermostat. I think I'll let them do these checks but I'll add your suggestions to the list & ask them to look for exhaust gases in the coolant, too, just in case (& with fingers crossed).

The work will be done during next week, all being well. I'll post the outcome.

Thanks again.

Jack