New thermostat now losing coolant!

Hi folks,

I've recently had the thermostat replaced on my rangey (2003 4.4). Had the thermostat fault come up the code reader so bought the part and had it fitted.

Garage advised I top up my coolant when I got the car which I did by about a litre. Since then (3 weeks) I've noticed that the coolant level has dropped a couple of times so topped it up. Got in tonight and the check coolant light came on, checked the level and it was virtually empty!!

All in all I've put about 5 litres in since the thermostat change which can't seem right!!

Checked the oil no water in it. No misfire and no exhaust fume smell in the coolant so I'm fairly happy the heads haven't gone. Can only guess it's a leak somewhere but can't see any moisture anywhere!!

Can anyone point me to an obvious place that the water could be escaping from? Radiator and pipes seem fine as does the header tank. Could the new thermostat be to blame? Could it be an air lock causing pressure and escape somewhere??

Thanks in advance for the tips!!

Possible air lock!!

On the V8 BMW M62 engine there is a manifold hidden behind the engine with 2 pipes that connect it. These pipes have been known to start leaking or the manifold gasket perishes.

It is difficult to diagnose this area as the coolant drips onto the hot engine/gearbox and evapourates leaving little or no trace of the origin.

Take the pollen filter housing off and check behind the engine and see if there is anything obvious.

The L322 heater matrix is not know to leak as a common fail item, but that is not to say it won't spring a leak...check your footwell carpets too.

Rad is common to leak
Most need changing in their life

Saint.V8 said:

Possible air lock!!

On the V8 BMW M62 engine there is a manifold hidden behind the engine with 2 pipes that connect it. These pipes have been known to start leaking or the manifold gasket perishes.

It is difficult to diagnose this area as the coolant drips onto the hot engine/gearbox and evapourates leaving little or no trace of the origin.

Take the pollen filter housing off and check behind the engine and see if there is anything obvious.

The L322 heater matrix is not know to leak as a common fail item, but that is not to say it won't spring a leak...check your footwell carpets too.

Click to expand...

Cheers for the info saint...

What's the best way of flushing an air lock out will it need a full system flush or will idling with the filler cap off do the trick?

Re the 2 pipes at the back; where do they connect to and from? I've done the pcv valve replacement as per your guide this week so I've got a rough idea of the layout back there.

Re the heater matrix, I did have some dampness on the passenger side a few weeks back... Put it down to heavy rain and a likely leak in the windscreen seal. No problems since but now you mention it heater temperature isn't brilliant... Is the heater magic easy enough to get to and check?

2.0_hippo said:

Rad is common to leak
Most need changing in their life

Click to expand...

Cheers hippo; rad looks fairly new, although I can't say for sure a spat of the service history was misplaced by previous owners!! I can't see any noticeable leak or moisture but is there any obvious way of telling if the rad is the issue.

For some reason the car is still throwing up a thermostat fault!!!

Been on a short run this morning, 12 miles, and checked the hoses- top hose is hot bottom is cool; but coolant temp is showing up at 99.5 degrees so presuming that it's not hit the right temp to activate the thermostat.

What could be causing the thermostat fault seeing as it's a new unit?

Najainitro said:

For some reason the car is still throwing up a thermostat fault!!!

Been on a short run this morning, 12 miles, and checked the hoses- top hose is hot bottom is cool; but coolant temp is showing up at 99.5 degrees so presuming that it's not hit the right temp to activate the thermostat.

What could be causing the thermostat fault seeing as it's a new unit?

Click to expand...

Water pump failing? duff stats are also not unknown, however if there is a water leak it will also be losing pressure which could account for overheating although 99.5 sounds normal to me.

Datatek said:

Water pump failing? duff stats are also not unknown, however if there is a water leak it will also be losing pressure which could account for overheating although 99.5 sounds normal to me.

Click to expand...

Touch wood it's not overheating at present. I did wonder about the water pump myself tbh - is there any way of testing or checking without removing it?

Pressure wise, the header tank will spew water out when up to temperature so I dont think there's a lack of pressure there...

I'm going to try and source some uv dye to see if I can trace a leak somewhere!

Range rovers, who'd own one???!

Najainitro said:

Touch wood it's not overheating at present. I did wonder about the water pump myself tbh - is there any way of testing or checking without removing it?

Pressure wise, the header tank will spew water out when up to temperature so I dont think there's a lack of pressure there...

I'm going to try and source some uv dye to see if I can trace a leak somewhere!

L322 Range rovers, who'd own one???!

Click to expand...

Edited for accuracy

Very true!

Cheers for all the help guys, think I may have solved it!

Bought 2 25ml bottles of ring rld2 uv coolant dye for £7 odd this afternoon; dropped in the coolant and ran it up to temp. Shut it all down and got a uv light over it (cheap one if bought off eBay a couple of years ago). Hey presto, the back of the engine lit up bright yellow!!

I think I've cracked it... Just below the pcv valve is a thick rubber pipe and connectors which on inspection has a small split in it.

As a temporary measure I've smothered it it high temp sealant just to close it up for now, although I suspect pressure will soon see the sealant off.

Does anyone know the part number or name? Alternatively I'll get it off and make one up myself.

Najainitro said:

Very true!

Cheers for all the help guys, think I may have solved it!

Bought 2 25ml bottles of ring rld2 uv coolant dye for £7 odd this afternoon; dropped in the coolant and ran it up to temp. Shut it all down and got a uv light over it (cheap one if bought off eBay a couple of years ago). Hey presto, the back of the engine lit up bright yellow!!

I think I've cracked it... Just below the pcv valve is a thick rubber pipe and connectors which on inspection has a small split in it.

As a temporary measure I've smothered it it high temp sealant just to close it up for now, although I suspect pressure will soon see the sealant off.

Does anyone know the part number or name? Alternatively I'll get it off and make one up myself.

Click to expand...

Good find...that is one of the pipes I mentioned that goes to the coolant manifold on the back of the engine....

I think it is this one referred to at:

Range Rover MKIII - Rear Engine Coolant Leak

And as luck may have it, I decided to change all the piping on my car and gaskets etc and bought one, then, since I have LPG, realised I didn't have one to replace!







pm me if you want it sent over (for a price of an exotic pint) as it's no use to me - that being if it is it.

Charlie