jesperjes · Mar 7, 2016

I have a 110 TD5 from 2002 with 250.000 km on the clock with the lack of heat inside the cabin. The engine itself and the needle in the dashboard behaves as it should.

I noticed that the hose that goes into the heater matrix is cold when the rest of the engine is warm. So I thought it was the heater which was blocked. I flushed the matrix. This did not change anything. So I took the two hoses from the heater and assembled them together, thus bypassing the heater. The hoses were still not hot, so the heater is not the problem.

I have found out that if I drive 90 km/h in 3rd gear then there's lovely crisp hot air in the cabin, but when I change up in 5th gear the heat disappears. But at 120 km/h the heat is back.

I have also changed the thermostat without success.

I can not find any constrictions in the hose up to the heater. So the only thing I can imagine that remains is that water pump is not working properly.

Does that sound reasonable? I can not see any leaks around pump (which I have read would be a sign that the pump is faulty)

Is there anywhere else I should look?

Jesper

reject86 · Mar 7, 2016

if you can't feel hot water in the pipe to the heater matrix I'd look at the control at the valve end, ensure that it is working fully in both directions when the dash lever is operated? Maybe the matrix is just silted up - new ones are only about £35.

flat · Mar 7, 2016

reject86 said:
if you can't feel hot water in the pipe to the heater matrix I'd look at the control at the valve end, ensure that it is working fully in both directions when the dash lever is operated? Maybe the matrix is just silted up - new ones are only about £35.

What do you mean valve?

The matrix is always 'hot' - the lever on the dash just either diverts air over the matrix or not, but water flows through it regardless.

You may need to flush the matrix again a few times, and the rest of the coolant system.

The thermostat could still be faulty even if new, check it in a pan of water.

Would be worth getting some UV dye in the coolant and pressure checking the system.

jesperjes · Mar 7, 2016

I bypassed the heater matrix by disconnecting the two hoses from the heater matrix and then joining the two hoses. The hoses still didn't get hot. Therefore I don't think the matrix is the problem.

flat · Mar 7, 2016

jesperjes said:
I bypassed the heater matrix by disconnecting the two hoses from the heater matrix and then joining the two hoses. The hoses still didn't get hot. Therefore I don't think the matrix is the problem.

Okay, maybe a coolant channel in the head is blocked, have you flushed the rest of the coolant system?

Try the stat in the pan.

IIRC the water pump impeller can come off the spindle so even if it's turning it won't actually pump water.

Might be worth checking

flat · Mar 7, 2016

What does the rest of the system do?

How do the pipes feel? What does the radiator feel like top and bottom?

reject86 · Mar 7, 2016

flat said:
What do you mean valve?

The matrix is always 'hot' - the lever on the dash just either diverts air over the matrix or not, but water flows through it regardless.

You may need to flush the matrix again a few times, and the rest of the coolant system.

The thermostat could still be faulty even if new, check it in a pan of water.

Would be worth getting some UV dye in the coolant and pressure checking the system.

Oops yeah scratch that this isn't a series 3

.

jesperjes · Mar 7, 2016

flat said:
What does the rest of the system do?

How do the pipes feel? What does the radiator feel like top and bottom?

The rest of the system feels normal ie. all hoses are hot. I'll check the radiator when I get home today.

I'm not an expert, but isn't the thermostat placed after the hose to the matrix? The top radiator hose is hot and from the this a thinner hose goes to the heater matrix. This hose is hot a the junction and then decreasingly cooler on the way to the matrix.

neilly · Mar 7, 2016

You could try, but on your own head be it,

Make sure there is plenty of coolant in the expansion tank. raise tank and add coolant a sif going to bleed the system.

Take out the bleed screw on the top rad pipe, start engine and rev it up , the coolant i would have thought would create a fountain if the pump is running, if you rev harder it would get higher. Stop and make sure system is bled correctly.

If there is no or little flow ,I would suspect the pump is not working correctly

You might want to get a second opinion on the above procedure .

jesperjes · Mar 7, 2016

neilly said:
You could try, but on your own head be it,

Make sure there is plenty of coolant in the expansion tank. raise tank and add coolant a sif going to bleed the system.

Take out the bleed screw on the top rad pipe, start engine and rev it up , the coolant i would have thought would create a fountain if the pump is running, if you rev harder it would get higher. Stop and make sure system is bled correctly.

If there is no or little flow ,I would suspect the pump is not working correctly

The picture you attached is from a Disco, here's a picture from mine with temperature indications

There is a fountain when the engine is idling and the bleed screw is removed, I haven't tried to rev the engine without the screw....

I think I'll try to flush the hose that goes over the head of the engine and to the matrix.

neilly · Mar 7, 2016

Hi Jesperjes,

The picture is from the defender 1999 - 2002 rave manual. Have to love Landrover publications.

Good luck.

Cheers

jesperjes

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