Lancia Delta cooling diagram

Work that out!

The only part that hasn't leaked or dripped on our Evo engine rebuild is the cheaply reconditioned radiator, although it has been in and out a few times.

The cooling system has now thrown up another problem, the fan only works at high speed.

After the engine was installed and run up to temperature, the gauge reached 100 before the fan cut in, the fan then running at its higher speed. In further tests the fan cut in at a lower temp, but still at high speed. I assumed it was the radiator temp sensor,

which I have never changed.

another bucketful

Draining the radiator, again.

Lancia Delta coolant switch

Coolant temp fan control switch

I ordered a new sensor switch from AECar, to fit this the rad has to be drained. Again!

I first tested the fan motor and its contacts, I had printed out the fan wiring diagram, and after some research I grounded the red wire, and the fan worked fine. At high speed.

I hadn't refitted the bumper and grille yet, and the bonnet was still off. This made the job much easier, and although it's a pain, if you do this job I would suggest removing these items too. I removed the intercooler shroud to access the radiator pipe clips, then drained the coolant from the system at the turbo coolant pipe, into a clean bucket.

When drained, I slackened the pipe clips and removed the 2 x 13mm bolts at the top of the rad, then I drew the rad forward, pulling off the main pipes. After unplugging the temp switch wires, and removing the cable securing clip, the temp switch is simple to remove. Like Kylie did working in the garage on Neighbours, I used a big shifter. It is an M16 27mm size.

Delta intercooler frame

Extracting intercooler shroud

Delta intercooler switch

Removing temp switch

coolant switch

Temperature switch

I fitted the new switch with just a smear of sealer, making sure not over tighten it, the torque is 4.9nm, set here by my arm.

 I fitted everything back and filled the system with the saved coolant.  I ran the car up to temp, and it was exactly the same, bugger! 

temperature rising!

Start up and test after new rad switch fitment, temperature on its

way up again!


A depressing sight after all my careful work. Integrales are not merciful on people who make assumptions.

I found a simpler diagram on the internet, this shows a red wire to a 25amp fuse, then it goes to the motor, then through a resistor to a relay, the relay is controlled by the 2 position radiator fan switch, this sends the juice through the resistor or grounds the system directly,

giving the 2 speed fan. I think.


I found this difficult to understand, it seems back to front. I re-read the diagram several times and it did begin to make sense. To complicate things, there's a thermal switch which seems to isolate the whole caboodle if the system overheats.

I ordered a new resistor and a relay from AECar.

Evo1 fan relay

A lovely new relay and resistor, the resistor looks more durable than the old one's exposed coil. It looked like it wouldn't fit, but it did, perfectly!

Lancia cooling wiring diagram
Integrale coolant resistor

The parts arrived quickly and were soon fitted, the black relay lives under the passenger side dashboard, and the resistor goes at the top of the fan shroud. So mercifully, no more draining was required.


I ran the engine up to temp again, and it all worked fine. Looking at the condition of the old resistor, I would say it was the fault.


It's difficult to to tell what the cooling fan is doing when you're motoring, if the engine stays cool, then all seems well. The engine thermostat opens at 81-85oC, the fan switch operates at 82-87oC, then high speed at 87-92oC, so the engine's happy designed operating temperature is about 85oC.


The outcome of the repairs was satisfying, this car has had doubtful cooling for many years. The system now works very well as Lancia designed. 

This Evo1 has always been a favourite, it's seen some action in the hands of past owners, and us too. It's a brave and happy car, and now it has the original engine

this Delta was born with, rebuilt and ready to roll. 

Lancia Delta Evo1
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