2.0 VXi overheating advice please

[John Clements]

My 2.0 XE has recently developed a slight overheating problem and I'm hoping to get a few pointers from any members out there who can help.

 

Basically, the water temperature rises steadily and continues to rise past the 100deg mark on the temperature gauge and the fan does not automatically cut in.

With the car in motion at a reasonable speed the temperature does stay at the correct level (between 80-90deg), so I have discounted a head problem.

 

My first thought was that the radiator fan switch on to of the Rad was faulty, so I replaced it. This did not resolve the problem (maybe I have been unlucky and the second switch is also faulty).

 

As a short term fix I have fitted a piggy back switch to the fan switch and can operate this from the cockpit, manually switching this on does bring the temperature down when the car is stationary.

 

However, when returning from a run in the car, the coolant in the expansion tank appears to remain very full and does not go down to the correct level, even if left for an hour or so.

 

After running the car, all of the water pipes and radiator are hot, so I guess the coolant is circulating ok.

 

Could there be a problem with the sender unit or thermostat? are there any easy/recommended tests that I can do without having to start draining the system.

 

I'm hoping to do a long run in about a weeks time and would prefer to do it without having to worry about overheating, so any advice would be greatly appreciated.

 

Thanks in advance

John C

M7 RSJ

[Foxy Smith]

The standard Vx thermostat opens at something like 92degC 92-108 on the thermostat. You can replace this with a thermostat for a Calibra Turbo which opens in the low 70's This gives a rock solid 82 on the gauge. Prior to this I was getting huge oscillations in temperature. Apparently the problem is the Caterham gauge set up but I'm happier now seeing a steady temperature.

[John Clements]

Thanks Foxy Smith, I might give that a try. Although, I've been running the car for nearly four years now and this problem has only developed in the last couple of months. Prior to that the temperature always seemed fairly steady (according to the temp gauge anyway).

[Bob Simon]

70° fan switch for 924/944/968 Porsche here, near bottom of page, fits the 22x1.5mm hole in the Caterham rad. Much more reliable than the CC bit.

 

 

-Bob

94 HPC VX

 

[EFA]

John,

 

The fan switch may well be in an airlock.

 

From cold, remove the expansion bottle cap, jack up the front of the car so the expansion bottle is higher than the top of the engine.

 

Undo the blled screw on the rad and have the tools and an old towel to allow you to refit when the coolent is very hot!

 

Start the engine and let it warm up to 80 degrees. Dip your finger in the expansion bottle and you will feel water heat up as the stat opens. If this does not happen by 100deg, you have astat problem. Buy the turbo type mentioned above, fit it and repeat the whole process.

 

 

Assuming coolent in the expansion bottle does get warm, bleed all air out of the top of the rad and do up the bleed screw.

 

Let the car get hot until the fan cuts in or the gauge hits 100deg. DO up the expansion bottle cap.

 

If the fan still does not come on, short out the two wires going onto the switch. be carefull doing this - the motor draws qwuite a current and you'll get a small spark as you make the short. If the fan works, but a new rad switch, fit it and repeat the whole process.

 

Mop up the floor - this method is messy but very effective.

 

For info: 90% of overheating problems on Sevens on the Le Mans trip (hot weather etc) are airlock related.

 

 

[EFA]

And having read your initial post again....... the level in the expansion tank does not vary as you would expect. Don't be tempted to think it does, even when things work properly.

 

 

 

 

[John Clements]

Thanks for the info Arnie, I will try all of this tomorrow.

Re. your second post relating to the coolant level in the expansion tank. In the beginning the level was exactly at the recommended fill line, when hot the level completely fills the tank and stays that way for a long time after, is that what you would expect?

[John Clements]

Bob,

Thanks for the link, if it turns out that I do need another switch I will give your recommendation a try. It'll be my third switch in 12 months, so hopefully will last a bit longer.

 

 

[EFA]

John,

Your comment describes exactly what I would expect. Its not so cirital if their is no air in the expansion tank - thats why the lid has a relief valve.