Cooling/fans Help Please

[2052006 10]

Having rebuilt my 205, engine back in, I had it running up to temp, fan kicking in as it always did and seemingly bled ok. I am using a BBM hose kit throughout with my gti6 engine.

 

Passed MOT, so took it for it's first "blast". Didn't get more than about 6/7 miles as I noticed the coolant temp gauge going past the point where it would normally sit, so stopped and noticed rad fan was not working. So tested fan using brown "test" plug (this has a green centre wire, with a blue and white wire either side). As I understand it, bridging the centre wire to each wire either side, will run the fan on either the low speed or high.

 

However, it only worked with the green and blue wires bridged - and I can't say whether this is low or high speed - anyone know?

 

I thought it must either be the rad temp switch or the resistor (silver cylinder).

 

I changed the rad temp switch, as I had wanted to put a lower temp one in anyway. Tested it this morning, but still fan does not kick it (turned engine off once it had got to about the penultimate line on the gauge - approx 100 deg, I think). The fan used to kick in at the line before this (about 90).

 

I then bridged the two wires (blue and white) going to the resistor plug (I think it's quite common to do away with the resistor, cut the plug and connect these two wires, to do away with the "low" speed - right?). But this had no effect on activating the fans either, when run up to temp.

 

I'm rather confused as to what's going on here.

 

Any thoughts?

[Simes 248 2 Cars]

Quick thoughts ignoring the fan issue.

The fan doesn't normally run when moving only when stationary. As soon as you drive air enters through the rad and the temps drop.

Therefore if your car is overheating when moving there is something else wrong.

 

Have you removed the blanking strip below the bumper in the valence?

 

Have you bled the coolant fully and removed air?

 

If the resistor is broke then the high speed fan kicks in as default.

 

Does the red overheating light come on? I wouldn't worry if it doesn't. Obviously check the light works first!

 

 

Out of interest what fan are you using?

I'm running a standard rad, lowered and tilted and have no issues. I have binned the standard cowling and fan and have a revotec fan pulling the air through. Never overheated even in ambient temperatures of 38degc!

[2052006 10]

Thanks Simes, you make a good point about the fan not running when the car is moving. Could it be that an air-lock is preventing the coolant circulating properly and therefore not triggering the rad switch?

 

Thing is, I thought I had bled it properly, and I had it idling up to temp, being driven around (albeit slowly) and MOT'd (where it idles for a good long while), without a problem, fans kicking in etc. It was all as it should be.

 

Is it possible for an airlock to suddenly develop (please don't say head gasket!).

 

Have just tried to run it up to temp from cold again. Expansion cap removed, and as it got to 90, it almost boils over. Also, top rad hose is not getting as hot as it should and plastic entry pipe on top of rad is stone cold.

 

It does have a new 83deg thermostat. So, could either be a faulty stat (but it was working fine before, and is brand new), or could an air-lock be preventing coolant from flowing past/through stat?

 

Anything particular need doing when bleeding a gti6 set up (plumbed the BBM hose way)?

 

P.S. Standard fan setup from original 1.6 car, albeit now with a lower temp rad switch.

Edited December 27, 2014 by 2052006

[jackherer 543]

If the thermostat or something else is preventing flow you should be able to tell by feeling the top rad hose and the rad itself to see if they are hot.

[2052006 10]

If the thermostat or something else is preventing flow you should be able to tell by feeling the top rad hose and the rad itself to see if they are hot.

Top hose is slightly warm, rad cold.

 

Clearly, it's not circulating properly at this point.

 

It has a brand new correct spec stat, which was working properly when first install a few weeks ago. Is it likely to have failed so quickly? If these are the symptoms, is it more likely to be failed stat or an air-lock, do you think?

 

It was a Circoli stat from carparts4less - cheap, but any known issues with these?

[jackherer 543]

You can test the stat by putting it in a pan of water and heating it up so you can see if it opens.

[Miles 331 1 Cars]

Which Stat, Silly question but it should be the std 16v one

[2052006 10]

Standard 83 deg one.

[2052006 10]

I'm thinking it may just be air in the system. Managed to get the top rad hose nice and hot and also the plastic rad entry pipe, so I think the stat's working ok.

 

But the lower rad hose (from rad to metal pipe) was hardly warm and the bottom of the rad, stone cold. Should it be like this at idle (car stationary)?

 

Gauge got well past 90 and fan still didn't come on (My rad switch is supposed to switch on at 92) and coolant was about to overflow out of expansion tank.

 

Blocked or air in rad/lower hose do you think? Bearing in mind rad is brand new.

[Simes 248 2 Cars]

Air.

You can bleed these without even running the engine.

The gauge is not an accurate measure, the red light and stop light are, ie...danger!

[2052006 10]

What's the correct way to bleed these then? (Gti6 with BBM hose setup). The red/stop lights have not come on, so hope I've not overheated it during this episode...

[welshpug 1,666]

open bleed points and fill till coolant flows out of each one.

[2052006 10]

I have just one bleed point, on stat housing. Don't have one on rad (it is a cheapo Bolk one - could this be why I'm unable to bleed it properly?)

[Simes 248 2 Cars]

Ok,

One on hose entering the matrix

One adjacent to the thermostat on mi16.

 

There isn't normally one on rad.

Fill up tank and then do each tap up as the air is bled out in the order I stated above.

[welshpug 1,666]

no, theres a small bore bleed pipe from the top right corner back to the expansion tank.

 

The other bleed point should be on the heater hose

[2052006 10]

Don't have a bleed point on the matrix hose on the BBM hose.

[2052006 10]

Would it matter which way the BBM hoses are connected to the heater matrix pipes at the bulkhead? I've realised that my "T-piece" pipe (header tank/rear metal pipe one) is connected to the lower heater pipe. Looking at the BBM website, this hose is described as going to the top heater pipe. Would this affect coolant circulation and give bleeding problems like I'm seeing?!

[welshpug 1,666]

given the lack of bleed point it may help to swap them but I doubt it would change much as the matrix is lower than the pipes.

[2052006 10]

I will try swapping them over as I'm out of ideas. Spent all afternoon trying to get it to bleed properly, with no success. I'm sure the rad isn't getting hot enough, which explains why the temp switch won't work the fan, but cannot work out what's wrong

[2052006 10]

Twas the stat after all. Would not open at all in a pan of boiling water. So, I would not recommend the el cheapo carparts4less item which can be had for about £4 (though to be fair, they are refunding me). Lasted about 25 miles!