9 replies to this topic

[Steve Crisp]

Hi, A mod I'd like to try for the comming Summer. I'd like to be able to get the cooling fan to cut in below 100. Lets face it, why does it need to wait until it's around 106? It only goes above 95 when I'm stuck in traffic anyway. We've all sat there slightly worried as it climbs over 100 - waiting for the fan to kick-in. The thing is, how do I do it? I'd like to be able to adjust the stting somehow but the best I can come up with is just a manual switch that'll provide power to the fan ignoring the relay - not very good! Any ideas? Steve

[JG]

why? high pressure systems are quite happy at up to 115 degrees or so. Its not doing any harm. IIRC fans don't like the airflow from a car in motion when they are on. If you manage to get the fan to come on at 95 is will be kicking in more of the time and sometimes while the car is moving. The system works rather well as it is. It only ever kicks in traffic at 106 and brings it back down to 100

[ianrm]

GM/Vauxhall build thousands of engines for all climates worldwide and so I am sure the 106 cut in temp is well within the engines reliability limits. If it was cutting in as low as you said you'll probably find the fan would cut in a lot more whilst sitting in traffic and drain your battery.

[vxr36]

Mine comes on at 97 and goes off at 93. It is standard and has not been modified. I've only seen it above 100 on really really hot days

[Mr_M]

Mine comes on at 97 and goes off at 93. It is standard and has not been modified. I've only seen it above 100 on really really hot days

iirc the turbo/vxr fan cuts in a lot sooner than on the n/a

[2-20]

You can install a switch and control it manually when needed... i.e cooling laps during track days.

[Steve Crisp]

I guess it's because I know that water boils at around 100. IF your system ever depressurised for some sad reason (header bottle leak?), then it would boil away before the fan ever kicked in. I had a supercharged mini during the late sixties. The only way to limp home when the head gasket blew, was to remove the rad-cap and depressurise! Okay. So it's a bad idea, but we all worry about the strangest things... Steve

[Anarchy]

It had croosed my mind too, especially when sat still in traffic and you see it rising but even slowly start moving and it soon drops again. A manual switch seems like the best idea, then you can flick it on if your sat in a jam or cooling between laps. A related question, the car seems to cool faster when the engine/gearbox is being turned faster ie. in a jam in first gear rather than second/third. Is the cooling performed by just the wind past the radiator or some sort of circulation pump that speeds up with higher revs? I once had a car overheat and cracked the cylyinder head it was a Rover engine tho and aparently TADT sir

Edited by Anarchy, 04 March 2006 - 06:28 PM.

[Arno]

When putting in a manual switch for the fan, be careful not to engage it when driving more than something like 40mph. Otherwise the powered fan + the air velocity from the car driving will over-rev the fan itself and the motor will die on you pretty rapidly if you keep it up. (and replacing the fan is not a nice job.. clam off and all that...) It's a good idea to add a small circuit that's linked to the speed-pulse to block/disable the manual switch so you can't forget to turn it off and drive too fast. The 111R and Federal Elise with A/C do switch on the fan(s) (the A/C equipped cars have 2) sooner, but at a reduced rpm and it automatically disables the fans again if the speed of the car exceeds a set limit. Bye, Arno.

[john_s]

A related question, the car seems to cool faster when the engine/gearbox is being turned faster ie. in a jam in first gear rather than second/third. Is the cooling performed by just the wind past the radiator or some sort of circulation pump that speeds up with higher revs?

The water pump's driven by the engine (on most cars - can't think of any that have an electric pump), so the higher the revs, the more water gets pumped round the cooling system to the radiator where the heat can be dissipated.