Am I just being a bit thick? 1.8T cooling system

[SD1too]

Originally Posted by __chris__

Demist test:
Can't hear anything obvious when I put the demist on from cold.

That's problem number one then Chris. The radiator fan should start within a few seconds with 'demist' pressed and the engine running. Your fan's slow speed isn't working. If this isn't causing the overheating, it's certainly contributing to it, so it needs repairing straight away.

There are two types of fan fitted to the 1.8; with and without resistor. At the bonnet, peer in through the radiator grille. On the fan blade shrouding can you see, at about the two o'clock position, a rectangular silver resistor with an electrical wire connected to each end?

Simon

[__chris__]

I'm going to pop out to check the type of fan fitted once the hailstones have stopped and will report back.

(Wondering whether it would make any difference that there's no refrigerant in the air con at the moment. I was told that it had been discharged when the radiator was fitted a couple of weeks ago and I've not been anywhere yet to have it refilled.)

[SD1too]

Originally Posted by __chris__

Wondering whether it would make any difference that there's no refrigerant in the air con at the moment.

It possibly might Chris. With no refrigerant the compressor will be disabled and so the fan would not be required for air con. operation.

O.K., the alternative is to activate the instrument pack diagnostics (see "how to ...) so that you can monitor the coolant temperature. Drive the car until it reaches 104 degrees when the radiator fan should start running. You'll have to get out of the driving seat to check.

By the way, the garage which discharged your air con. should have recharged it again after the radiator work. It's standard practice to pay once, for both operations.

Simon

[__chris__]

Originally Posted by SD1too

At the bonnet, peer in through the radiator grille. On the fan blade shrouding can you see, at about the two o'clock position, a rectangular silver resistor with an electrical wire connected to each end?

Simon

Weather has improved... Yes there is a silver block where you describe.

[kaiser]

This is a bit stupid, but here goes.
Have you, yourself!, checked the level in the expansion box?

[SD1too]

Originally Posted by __chris__

Yes there is a silver block where you describe.

O.K., well first we have to find out whether your slow fan speed is working like this:

Originally Posted by SD1too

... activate the instrument pack diagnostics (see "how to ...) so that you can monitor the coolant temperature. Drive the car until it reaches 104 degrees when the radiator fan should start running. You'll have to get out of the driving seat to check.

Simon

[bishbashbosh]

Bit if info whether it may helps sort/diagnose your problem, I have recently purchased a Rover 75 with the 1.8 Turbo. I was not convinced that the fan was operating correctly/at the right temp. Anyhow plugged in my diagnostics tool and can confirm the following information (I also crossed checked the data from this forum and others and can confirm that my fan is operating correctly)

Demist not switched on
Slow speed fan comes on at engine temp 103/104 deg c
Slow speed fan continues to run until temperature drops to 96 deg c

At this point I thought the fan speed seemed high not slow, I disconnected the temp sensor wire, this causes the ECU to assume fault and switches fan speed to high, so could confirm "normal" slow speed was operational.

Demist switched on.
Slow speed fan comes on irespective of engine temp.

Can confirm that if aircon has no gas/fault fan may not come on (I will confirm this for sure at a later date when I service the aircon)

My car has a two speed fan with the three wire motor, so no resistor. If yours has a resistor and has lost its low speed, easy fix, how to on this forum and others.

[E_T_V]

Slow speed works on my 1.8T. Demist test doesn't work though as the aircon needs a refill.

[__chris__]

Originally Posted by kaiser

This is a bit stupid, but here goes.
Have you, yourself!, checked the level in the expansion box?

Yes - promise you I do this most days

[__chris__]

Update:
Removed the original PRT and boiled it up. Horrible looking inside but did actually open.
Put the new one back on anyway as it looks cleaner and I know from yesterday that it too opens.

Gradually refilled, started it up and ... no change.

Top hose is hot where it comes out of the engine across the T-Piece heading to the radiator.
Radiator however is still cold.
Bottom hose going into the stat is therefore cold.
Water in the expansion tank remains cold.
All despite the fact that the onboard diagnostics are telling me that the engine is reaching > 112 and the emergency fan is cutting in.

(I'll deal with the slow speed tomorrow when Jules' golden resistor arrives)


There was no warmth coming out of either the driver or passenger side heater, so I am wondering whether

a) The matrix is bunged up with something that is stopping circulation
b) The pump is not pushing the water round the system

Unless you can think of anything else ???
Your advice as to the next step would be much appreciated
I keep hoping that I'm just one last fix away from having a car that I can be happy with.