fan switch?

tris · Post by **tris** » 17 Nov 2004, 22:29

When should the fan switch on the radiator kick in? The fan definetly works as i tried bridging the connection with some wire. Ran the engine for 5 mins at idle after a run but the fan didnt kick in.
Should I worry?

Kowalski · Post by **Kowalski** » 17 Nov 2004, 22:31

Was the engine hot when you started idling? Was the bonnet up or bonnet down? What car? What engine? What did the temperature gauge say whilst this was happening?
If the engine was cold, it will take far more than 5 minutes of idling to get the fans to come on. With the bonnet up, I know my fan will only come on when the weather is hot, it seems you get more convection through the radiator with the bonnet up.

tris · Post by **tris** » 17 Nov 2004, 22:34

'93 cit ax 1 litre.
Engine hot after run
bonnet up.

tris · Post by **tris** » 17 Nov 2004, 22:36

oh, and there's no damn temp guage!! that would make this a little easier ey!

Robin · Post by **Robin** » 17 Nov 2004, 22:41

tris, you may have to wait a long time for the fan to come on with the bonnet up and a 1 litre engine. From conversations elswhere I think the 1 litre petrols are rather overcooled so in this weather it is possible the fan would not cut in at all when idling with bonnet open.
Why do you suspect there is something wrong? Robin

tris · Post by **tris** » 17 Nov 2004, 22:50

maybe im just being paranoid. During its last mot the hose from the thermostat to the matrix burst, during i presume the high continuous revving of the emissions test. I replaced the pipe noting very slight oil contamination in the coolant.
Weeks later after a 400 mile journey to see my girlfriend I noticed the oil content in the coolant was far heavier. So this past weekend I took the head off and found as expected a blown head gasket. Luckily the head was still very straight needing no machining, and the job was a success. Engine is all back together and am just trying to figure out why the gasket went in the first place. The burst hose in the mot test would suggest an overheat yes?

mezuk04 · Post by **mezuk04** » 17 Nov 2004, 22:58

Im still actually quite wary about this myself, bought my ZX about 5 months ago and the fan never seemed to kick in, replaced the thermostat but no difference, cross wired it as you mentioned and it kicked in, but got the engine going to a good temp but never worked for me. It went for a service about a month after i got it and the chap said the fan kicked in so im hoping if i get stranded on the A1 in the lovely sunshine that it will work.

Robin · Post by **Robin** » 18 Nov 2004, 00:08

Argos sell a multimeter come tester with a temperature probe included. I thnk it is under £30 have a look online. It is worth buying if only for the temp read out.
As a very rough guide the fan will come on when the majority of the radiator is at 85 to 90 degrees. By this time the top hose is at 90 to 95 degrees and you really cannot hold the hose with bare hands.
The lower return hose will be cooler and quite possibly you could hold this one. It may be uncomfortable but not scalding.
The hose bursting when the engine was being revved is most likely a case of the whole system pressurising from the leaking head gasket. The system operates at around 1/2 to 1 bar, 7 to 15 lbs and has a pressure relief valve in the cap of the make up tank. Check it is operating or it will just over pressurise. The pressure helps to raise the boiling point a few degrees.
If all is well and the system does not pressurise within seconds of starting from cold then the head is probably OK.
Get a tester to check the head temperature! R