I agree.. it sounds like two problems, although the fan not coming on is the one that would get my main attention, since a tiny weep from the thermostat is not that serious in itself and just needs an occasional top-up to keep the beast going until the crystalised coolant drying in the space blocks the leak all by itself anyway...

Hylomar is supposed to be good for water-sealing mating surfaces but I dunno if the pink coolant is more aggressive than the old style glycol based coolants. I had a similar "how did I mess that one up" leak when I refitted a water pump recently. I'm blaming the coolant now..

The rule of thumb for thermostats is that they start to open around 86C and should be fully open at 90C. The fan is supposed to intervene at 92C and cool the engine down to 88C before knocking off.

If your gauge said 3/4 then that would be in the region of 105C. Without any antifreeze in the water, the system pressure alone (if 1.2 Bar) would prevent the beast from boiling over but a 50:50 coolant mix at the same pressure would run up to about 128C... which is around "Max" on the gauge.


Ralf S.

TTR its definitely worth investing in a OBD diagnostics dongle (£10 for a basic one) and the Torque app for Android. Using this you can add the coolant temp to display the exact temp and the fan. The dash gauge on half way has a 20C range so is pretty useless. Before changing the thermostat mine was running at 71C max, temp guage still said half. Italian engineering.
The coolant fan will kick in at max speed at 105C if the resistor pack is open circuit. The low speed kicks in at around 95C so in theory the max speed fan should never get used.
Normal operating temp is 85C.

Wardpaa

You lost me as soon as you mentioned Apps, electronic stuff is not my strong point :bang:

I’d love to get into the OBD stuff but just not got the competency

Will have a go at owt with a spanner but electric stuff gets the better off me.

Really interesting what you say and appreciate the insight you got from yours.

Will be trying to sort her car sometime this week with luck - work keeps getting in the way

Cheers again

No worries.
If you change the resistor pack for elimination then at least the low speed fan should kick in if idling for 10 to 15 mins in traffic.
It doesn't usually take long..

I'm new to this one, but it sounds to me like you have a faulty or incorrect new temperature sensor.

Can you check the resistance of the old and new sensors?

Robert G8RPI.

g8rpi

thanks for the advice

sorry cant do it anyway for two reasons - first no idea how to im not good with elecs at all unless i have an idiots guide to follow

and second not got old one as threw it way.

assume by the way the temp sensor you are referring to is the one attached to the thermostat housing - the one you unplug ?

im going to have a go at fixes tomorrow with luck and work permitting

i will update this thread with what i do

thanks again

Check the back of the radiatore for another sensor. I don't know 500 but some cars (maybe just those with the fan activated by the sensor, rather than by the ECU?) have the temperature sensor on the radiator. In that case the thermostat sensor only operates the temperature gauge.

But you could have a single-sensor (the one on the thermostat) doing everything.


Ralf S.

Eh up all,

Right with work etc only got limited time today so fixed immediate issue of the thermostat housing leak.

Traced the bl.#@y leak on the housing to poor casting and probably could have been a better seal perhaps , so I’ll take that one myself.

Looking at the housing and rethinking the £18.00 I paid which has the plastic heater outlet pipe I bit the bullet and spent proper money ( to a yorkshire man) on a Febi one. Quality was immediately different in my opinion. metal all round and well finished.

Fitted again carefully cleaning and drying block, hymolar blue on and sealed up square. Left to cure to be sure. Refilled and bled with heater on full and bleed nipple open to vent. Topped up with pink OAT.

Blasted heat out and no leak - just like last time and we all know what happed a week later

Let’s see what happens, not had chance to sort rad fan yet , due to my lack of elec knowledge it’s simpler for me to swop out the whole part at £65.00 ( that’s Christmas cancelled ) but will try and sus out first to see if rad fan kicks in now with new stat.

Thanks for all help on this will update when the next so99ing bit falls of next week, probably when or just after I’ve fit the new alternator belt next weekend

This car has character - jeckle and hyde :devil: