3VZ-FE Overheating

[hmmmmm]

Got a bit of a problem with my running mk2 v6. The radiator fans do work but hardly ever turn on.

After heating the engine up and letting it idle for a couple of minutes fan one and two turned on for about 30 seconds. When the dashboard meter was back in the middle the fans stopped and never came one again, meter was at the top and steam came out of the engine department, but fans didnt come back on..

Ive checked the fuses and they are ok, dont think its an electrical problem because they do work...sometimes. So im guessing it the thermostate. But how can i check this?

I was also thinking about making a switch in the dash to turn them on manually, has anyone ever done this? What would be the easiest way?


(searched through ALL the electrical topics but couldnt find anything about the thermostat/fan problems )

[snowtigger]

My alfa had a similar problem bloody electrics just change the sensor should be ok then, my fans just stayed on all the time and over cooled the engine which can naff it right up if not carefull.

[hmmmmm]

Ok so the switch is out, but what sensor needs to be changed? There is one in the radiator, and one in the engine block, are the fans controlled by one of the two?

[snowtigger]

Hmmm radiator would be for the fans and the block for the gauge I could be wrong, but here's a simple test disconnect the block one and run the engine till warm if no movement of the gauge then the other is for the fans or vice versa, if you disconnect the rad one and at your own risk short the wires does the fans come on if they do then change that sender as it's duff.
I hope that helps I may be wrong but it's what I would try, or wait till Paul logs on in the morning and puts us both on the right track.

[AlunJ]

Aye, the temp sensor in the rad controls the radiator fans and the one in the block does the gauge, same as the 4a.
edit: I'm sure you can test if the sensor is working properly with a pan of hot water and a multimeter, it's resistance varies with temperature but I can't for the life of me remember where I saw the graph for it.

Using a switch, would you be looking to just have just an on / off toggle, or permanent on / automatic toggle?

[Paul Woods]

To be honest if the fans come on once they have proved the electrics are working fine, what you have here is a poor circulation issue i think.

Have you seen my thread of the poor QH water pump design? When fitted with these pumps the engines would sometimes do exactly what you are describing, the fans would come on once after being revved, then the engine end would overheat, simply because the fan switch on the rad was not seeing the hot engine coolant due to the pump not being able to circulate the coolant at idle.

Do a little test, raise your idle to around 1500rpm and see what happens then, if the fans kick in and out with no problems then you have a circulation issue, my money is on the pump blade design or maybe even a thermostat not opening fully, but the pump issue is a very real one.

[hmmmmm]

Crap that would suck monkey balls.. Tnx for the info chaps!

Ive seen the pump topic a while back but didnt realise this might be the result.. Ive already got a new water pump for my project car but might end up putting it in this one, im thinking of selling it as ive got 3 cars already. But I dont want to sell it with any major faults.. So i guess ill have to bring out the spanners again..

[pilotpete]

:QUOTE=hmmmmm;226847]Crap that would suck monkey balls.. Tnx for the info chaps!

Ive seen the pump topic a while back but didnt realise this might be the result.. Ive already got a new water pump for my project car but might end up putting it in this one, im thinking of selling it as ive got 3 cars already. But I dont want to sell it with any major faults.. So i guess ill have to bring out the spanners again..[/QUOTE]

Good on yer - some people would sell it on and keep quiet.:thumbsup:

[phd68]

similar problem with my car. Two or three times now since my build was completed (Apr 08) i've noticed similar symptoms. Was initially concerned about the pump problem but I recall fitting the IezuraParts item which i'm almost certain doesnt have the QH problem. fan not kicking in at high temp, and engine temp noticed to be a needle width higher than normal when driving. Not been to bothered about it as i'm aware of it, so i havnt got round to checking other things out. However sitting here thinking about things, I'm beginning to think that the problem may lie with my coolant level.

I check the level now and again and it tends to drop approx 1-2 inches below the neck of the cap. I cant locate any leaks and no performance problems suggesting Its getting into the bores or oil system. So i just top it up. Could it be possible for the level to drop introducing an air lock that can get caught around the temp switch, preventing it from working at idle? Just a thought as i try to get motivated to look into it!!

[Garbe]

I think the issue with losing some coolant may stem from the overflow, and possibly not getting sucked back in when the temp cools down.

[phd68]

Ah, never thought about that Garbe. Could this be down to the distance that the overflow tank is from the filler point? I feel a mod coming on!!