300 TDI Auto Thermo Fans

[ghosta]

Hello to all. I have a 96 TDI300 Disco with auto transmission.

Ive had a problem with the Disco towing a caravan- sometimes after a long haul when I stop the car to refuel etc it wont start. Nothing- not a click from the solenoid. But if I wait 10-15 mins with the bonnet up it cools down and starts normally. Can be inconvenient blocking a bay at the service station!

Temp guage shows normal and no signs of overheating, although obviously hot under the bonnet.

It recently occurred to me that Ive never heard the thermo fans on the transmission cooler running. At idle the pair of them should make a pretty unmistakable roar. Im wondering if there is some sort of heat safety cutout on the auto transmission which operates because the transmission fluid is hot and the thermo fans are not working.

I looked in my Haynes workshop manual and there is NO mention of the thermofans at all. No circuit diagram either to indicate how they are connected and what device is supposed to turn them on.

Im considering cutting the wires and making a manual switch in the cab. Id turn them on hot days and an a hard uphill pull. But Id prefer to have them cut in when they are supposed to.

Anyone with any information can help?

[rrturboD]

I have suffered a similar situation with 'failure to start'. With JCs suggestion, I ran another wire from the starter solenoid so as to bypass the ignition switch. If the steering column switch fails to activate the starter, I use the wire I had installed in the engine bay, touch it on the +ve battery and bingo motor starts... so before you try/replace too many components, need to check that it may be the steering column switch.

[brianwood]

My D1 had a similar problem with the thermos. Both thermos were cactus (plain worn out) and there are 2 thermistor thingys on the thermostat housing which I replaced.
It now, as you say, roars when the aircon is on and when engine temp goes past half-way

[nice1guv]

A standard 300TDi has no cooling fans specifically for the transmission (I don't think). The fans up the front are for the air con and should swicth on when the air con is on.

An idea for the hot starting problem: check the big metal earth strap that goes from the starter motor to the chassis. Its on the passenger side of the engine below the turbo where the starter motor is. Mine was attached on a bad angle and touching something (can't remember exactly what) that caused the metal strap to start wearing through.

[nice1guv]

My D1 had a similar problem with the thermos. Both thermos were cactus (plain worn out) and there are 2 thermistor thingys on the thermostat housing which I replaced.
It now, as you say, roars when the aircon is on and when engine temp goes past half-way

Are the air con fans also thermo cooling fans?

[justinc]

The two thermo switches on the thermo housing are for A/C models only. One of the switches is a normally open contact, the other normally closed. The NC switch is for the A/C compressor control circuit, in the event of an engine overheat, it prevents the A/C compressor from being engaged. The other is a NO switch, it will engage the thermatic fans when the engine temp is high, A/C switched on or not.

JC

[ghosta]

Thanks for the replies- yes your right they are primarily aircon fans, and on checking the Haynes manual shows them under aircon, but no electrical diagrams.

Back to the starting problem, the earth strap and starter motor wiring was all checked. Could the solenoid switch fail ONLY when engine bay temps rose ONLY when towing a caravan ? (even though coolant temps are normal) I cant think of anything else.

[Iain_B]

I had similar problems, but not just when towing a caravan - starter would not work occasionally when the engine was hot - the hotter the day the more likely to happen. Eventuality it was every time after a hot shutdown,

Tried cleaning the terminals, new terminals (both solenoid and heavy current cable), heavier cables, new earth, wiring direct to the solenoid terminal, bashing with a hammer would sometimes work but a new starter fixed it.

[nice1guv]

Whoops, wrong thread. :o