Apparently Overheating K-series

[timbar]

You may have seen my previous post on the subject of bleeding the coolant system of a K-series.

 

My interest in the fluid level was triggered by the fact that my car had been apparently running mostly just under the red-zone (about 118 degrees) all the way home from Nottingham to Manchester, without ever going into the panic zone !

 

Having spent most of a weekend ensuring that the system was thoroughly bled and then taking the car on several shortish jaunts to check the cooling was working, I thought I was safe to drive the car to work in Nottingham (About 100 miles), and then to Leamington (Another 60 or so).

 

Unfortunately about 35 miles into the journey to Leamington the temperature started creaping up, (having run for the best part of 200 miles with no ill effects). Inevitably it went into the red, just as the tropical summer storm started. On arrival of the man from the AA, the car proceeded to idle for about 10 minutes with no sign of moving from 110 degrees. As soon as I pulled away from the hard shoulder with Arthur from the AA behind me, the temperature shot towards the red-zone. But as I pulled onto the hard-shoulder again ready to stop the engine it dropped a few degrees and then stayed happily just below the red again. Arthur (from the AA) checked the temperature and found that none of the pipes were above about 85 degrees. He also noticed that the temperature sender for the water guage was directly over the exhaust pipe and that the fan hadn't started, despite the fact that its sensor is only a few inches away. So the basic questions are these:

 

1: Is there a design fault in the positioning of the temperature guage on 1995-6 super-sport (1600 K-series) ? (This was AA man's idea)

 

2: Should there be lagging (is that what its called) on the water pipe that the temperature sensor is stuck into ? That might stop the apparent heat soak from the exhaust pipe. I've had the engine re-built and re-installed recently, so maybe they missed something.....

 

3: Any other ideas why my water temperature is indicated to be so high, when the actual temperature in the engine seems to be perfectly well under control (Or am I missing something) ? Or even have I just got an air-lock in the coolant system?

 

HELP! PLEASE!

 

 

[DonkeyDave]

there was a problem similar to this on the original R500s as the sender was in the incorrect position - this has been moved and the problem has been 'improved'

[Rob Walker]

I have had this problem, my car is a 97 K series, the fault was a high resistance joint on the end of the tiny wire that feeds the temperature sensor. I soldered the spade connector on and haven`t had a problem since except genuine high temperatures whilst on track days, see my thread.

[timbar]

Thanks guys, I'll try soldering the contact to start with, and get onto Caterham on Monday about any design changes they may have made in this area.

[Allen Payne]

Have you tried taking the sensor out and testing the gauge's reading by putting it in a kettle of boiling water?

 

 

[Roger King]

Interesting question this one. I've had several K cars on the rolling road that apparently suffered from very rapid heating of the coolant under load even though the engines were in good health.

 

My initial thought on this subject is that the temp gauge sender is immediately above the exhaust manifold and might be giving a false reading due to rising heat, but so far I simply haven't had time to look into this properly. On the rollers, the flow of cooling air over the exhaust is very poor compared with what would be seen in the real world driving situation, so this may not be relevant to Timbar's problem anyway.

 

Eventually, we'll get round to looking at this one.

[Tin Man]

I had a problem with the temperature gauge reading very high, just below the red. The fan would not come on untill the gauge almost in the red. I took the sender out & cleaned it up. Problem solved. I guess it was just a bad earth. Temperature now reads 85 deg.

 

Worth a try

 

All the best

[Mike Bees]

My temp. gauge sender is in the 'standard' position, i.e. in the water rail above the exhaust manifold. It's never caused any unexpectedly high readings even when the car is run on the rollers.

 

Mike

[Simos]

Although I have a BDR not a K, the temp sender is also right above the headers, this has never caused a high reading even though it gets so hot that the insulation has melted off the wire.

 

I have subsequently wrapped some shiny asbestos cloth around it to stop it melting any more.

 

I did over heat it at Cadwell when my water pump belt went AWOL and it did then read 110 to 120 which were real, but then I knew about that 'cos I had a footwell full of boiling green water.

[Simon Tidmus]

I have been having loads of similar problems with temperature readings on my K-series car, the car was a 1.4K but I then converted it to 1.8VVC but it still retains the 1.4 exhaust and temp sender. the temp will rise alarmingly in the oddest occasions which do not seem to follow any pattern of load or speed. I have tried all the usual bleeding and checking all the wiring but find the temp will rise about 10C when I turn the lights on! This I thought was due to voltage stabilisation but as ther is no voltage stabiliser in the instrument circuit, or any caterham circuit I'm confused. I was told that teh stabalisation was in the gauge but a new gauge and sender did not help. New earth leads direct to the temp gauge to isolate it from the rest of the gauges helped but I've run out of further ideas to try. I even ran with an independent digital temp gauge in the water pipe for a while and this just confirmed that the the temperature was very erratic!