Quick Diagnostic On Overheating

[Obey_R 23]

I took a long (ish) journey for the first time since I've had the pug on the road, yesterday, just over 100 miles each way. Now previous to this I have had no trouble with the engine getting hot, but I've never driven it in traffic prior to this.

 

Anyway, the trip there went fine, no problems at all. Temp. gauge sitting where it always does, at just abouit half-way. About 50 miles into the return journey we hit some traffic at a round-about, so queing for about 5 mins, then we pull off and get a drive-thru at McDonalds. By the time I come to pay I notice the temp gauge had risen and the light had come on, along with the stop light.

 

So I stopped, let her cool down for a bit then checked the expansion tank (something to note, there was no 'hiss' as I turned the tank cap?). There was a fair bit of steam, but it wasn't boiling. Anyway I topped it up with abotu 1.2 litres of water, left it for another 5 mins and drove all the way home with a bit of a traffic and the guage didn't move again, just sat about halfway.

 

Before it was MOTd I changed the thermostat, radiator cap, flushed the radiator 2 or 3 times and filled up with new coolant.

 

Also when the light came on in the drive-thru, the fans didn't kick in at all. I know they should have done so that's something I'll investigate further, but is there anything else that could have caused this or am I just worrying too much?

 

Could the waterpump cause problems like this, or is it just down to the hot weather, slow traffic and no fans kicking in?

 

Sorry for the long post!

[steve@cornwall 100]

First suspect would be the connections to the fan relay - the ally cylinder should be clipped to the rad. Connections often corrode and the fan doesn't cut in.

[Obey_R 23]

Isn't the ally cylinder the resistor? If this is faulty it should still come on at high-speed, no?

[maturin23 10]

If your fan isn't kicking in then that's your problem. Any car will overheat eventually when stationary if the cooling fan isn't working.

 

It's a simple, easy-to-understand, self-contained loom, take it off and check it for poor connections.

[Obey_R 23]

Yeah I will be checking the fans and wiring soon, I just wanted to check there weren't any signs of something more sinister. Thanks anyway

[GLPoomobile 958]

Happened to mine. At first I thought the resistor had failed, so I bridged the connections to overide it (making the fans come on full when they'd usually come on at half speed), but at a later date I reconnected the resistor and it worked, so it was just the usual duff connection caused by corrosion and brittle wires.

[SurGie 54]

Iv used WD40 or ferosol from Bilt Hamper to help get electrical connections working properly and can last quite a while. I have also recently bought some of THIS stuff, its good stuff. The brush that comes with it is pretty useless on small connections though, so iv used an old small art painting type brush. Its just like liquid tape and is very flexible.

[Obey_R 23]

Well there is only 6volts at the perm. live where the sensor connects. The fan runs fine hardwired to the battery, and also by running 12v straight to the high and low speed wires where the sensor is. So this leads me to think that the 6v isn't enough to power the fan and/or the thermoswitch is dead. So I'll replace the section of wire from the shuntbox to the thermoswitch and if it still doesn't work it'll be down to the switch, right?!

[smithy 1]

obey_r

 

i had similar issues with my fan not running further investigation found the pug loom to be fairly crap so i chucked it all away including resistor and wired it like this.

 

1 new temp switch in rad with only 2 connections,make sure it is same temp as the slow speed on standard switch.

 

2 temp switch now switches an earth for a relay coil,relay screwed to slam panel.

 

3 fused perm live to rad fan motor from shunt box with a link to the relay coil positive.

 

4 switched side of relay is an earth from body one side and then down to fan motor earth,use same thickness of cable as the original fan motor.

 

seems to be more reliable than standard as temp switch is only switching low current earth instead of high current live.

 

a couple of hours work to get it nice and neat but worth the effort in my opinion.

 

oh also check the connections in shunt box as mine were quite loose and due to the high ohms caused some melting of plastic shunt box.

Edited April 12, 2011 by smithy

[Obey_R 23]

Well I spent an hour sorting it out today at work. I had bought some decent cable with the idea of running a new live to the thermoswtich, as it was only getting 12v from the battery. Further inspection led me to opening the shunt box up, to find masses of corrosion! I un-wired it from the car and spend a while cleaning all the contacts thoroughly. It was so bad that the fuse for the fans had partially rusted through! It was the old type fuse with the exposed fuse wire. So after it's all cleaned up, new fuses and few connections everywhere I'm getting perfect voltage at the switch, where I was only getting 6v before.

 

I've got a new thermoswitch coming tomorrow but I'll hold off on fitting that incase it was just the wiring.

 

I've got a feeling that the state the shuntbox was in, also contributed to my 'clicky' starter and my battery problems! Time will tell...