water temperature issue

[Andy1912]

Hello,

I am a fairly new Caterham owner - the car is a 1998 k-series that has been upgraded with a r400 engine. Anyway, over recent times all has been well.

However, on a drive today I noticed an issue with the water temperature. What is happening is that immediately after switch on the temperature gauge moves up to about 110 degrees, and then slowly further up to 120 degrees. This is on the cusp of the red zone.

Coolant level look fine.

The only issue of note is that yesterday the car did seem to be overheating and when I got home I was fairly low on oil, which I promptly remedied.

Any ideas about what the cause of this may be and any thoughts about whether I should stop driving it / take in to a garage?

Thanks for your any advice...

Andy

[sjmmarsh]

Andy

What (apart from the gauge) symptoms made you think it was overheating? Failure of the temperature sensor is quite common so it is worth changing that, but if it is overheating I'd check the thermostat on the radiator first - if the pipes are hot but the radiator is cold, it is likely that the thermostat has jammed shut.

Steve

[Andy1912]

sjmmarsh said:

Andy

What (apart from the gauge) symptoms made you think it was overheating? Failure of the temperature sensor is quite common so it is worth changing that, but if it is overheating I'd check the thermostat on the radiator first - if the pipes are hot but the radiator is cold, it is likely that the thermostat has jammed shut.

Steve

Thanks Steve. I have had a closer investigation today.

Not sure it is overheating. I ran the engine, stationary, for about 30 mins this morning. The radiator remained fairly cool. The fan kicked in for a while after about 20 mins then stopped. The supply side pipes to the radiator are fairly warm, but the return side are pretty cool. All the while the temperature gauge read between 110 and 120 degrees.

The gauge operates as a switched oil/water temperature indicator and the oil readings are fine. So on the one hand I am thinking it's not the gauge. On the other hand, I am thinking that if it is the sensor then why isn't then sensor output triggering the fan?

I'm no mechanic as you can probably tell, but I have a decent understanding of electronics having been an engineer a few decades back...

Thanks again for your help....

Andy

[DCL]

No 100% sure about your car but the fan is probably controlled by the ECU and has its own sensor. The gauge sensor normally only does the gauge.

[Andy1912]

DCL said:

No 100% sure about your car but the fan is probably controlled by the ECU and has its own sensor. The gauge sensor normally only does the gauge.

Thanks for that which is good news. I'll see if I can find the parts number and order another temp gauge sensor.

[BertBert]

Or the fan is controlled by the switch in the top of the rad.

The temp sensor in the water rail is duff. Change it and all will be well.
Bert

[Andy1912]

BertBert said:

Or the fan is controlled by the switch in the top of the rad.

The temp sensor in the water rail is duff. Change it and all will be well.
Bert

Thanks Bert

[sundance002]

I had the same problem, turned out to be water pump belt had came loose

[spanky3]

sundance002 said:

I had the same problem, turned out to be water pump belt had came loose

That would be the cambelt but I think you'd have known if it had by the horrendous scrunkling noise...

OPs problem, either temperature sender in water rail is giving a false reading or a stuck thermostat so the coolant is only circulating through the water rail and straight back into the engine at the stat housing. Most likely the former but easy to check.

(Water rail is the black metal tube that runs along the engine above the exhaust manifold with a hose at each end)

[texr2000]

I would guess temp sender for the gauge if engine isnt actually over heating. i had 2 go on mine, there are 2 sensors in the pipe above the exhaust, the gauge is the one with single pin and the ECU one is the dual pin with a clip on connector

[spanky3]

Something else to add - the sensor has a tapered thread to make it seal.. Be careful when refitting as overtightening will strip the thread in the water rail.

[Andy1912]

Hi

I have been looking at this today again. It's a warmer day bit the hose that the temp sender sits in is quite hot, and likewise the radiator. I also can't see the coolant circulating - though not sure if I should - I am assuming so.

Anyway, I would like to do the easiest thing first, because the gauge reads 100 degree + even without the engine switched on, and replace the temperature sender. It has a few markings - "46 / 10" and "6811" and below the latter "-0.3". It is like a previous poster indicated, small brass with one connection. Can anyone point me toward somewhere I can buy another one?

Many thanks

Andy

Edited by Andy1912 on Sunday 5th April 15:38

[apexcone]

This may be a total red herring but air locks can be a major issue on Caterhams and do all sorts of funny things with the temp gauge. Jack the front of the car up as high as you can get it and slacken off one of the heater hoses.

[7ss]

Sounds like thermostat is most likely from your description. Have you changed the coolant lately? An airlock in the system is another possibility but that wouldn't happen out of the blue if it's been running fine. Do you have a heater? Has that been used recently? (for the first time since a coolant change) Radiators can seep from the join between the core & the header as well which would eventually give the same symptom.

[BertBert]

Just get a new temp sensor from Caterham.
Bert

[Andy1912]

Many thanks for the pointers. I have ordered a new sender from Caterham which should be here in a few days.

Andy

[Andy1912]

Delivered and fitted. Temperature no longer a problem as advised so many thanks all.

The new version of the sender has a different odd connection. I have managed to squeeze the old connector on but its all very Heath Robinson. Is there an adaptor or connector that I can crimp to make a more solid and professional connection?

Thanks

Andy

[anonymous-user]

Andy1912 said:

Delivered and fitted. Temperature no longer a problem as advised so many thanks all.

The new version of the sender has a different odd connection. I have managed to squeeze the old connector on but its all very Heath Robinson. Is there an adaptor or connector that I can crimp to make a more solid and professional connection?

Thanks

Andy

Is it the 150c brass sensor with the disc onto which the connector has to be fed in from the side? If so there is a similar one but with a thread, nut and washer terminal, to which can be attached a male spade with a ring, so that the female spade goes on properly.

Hosefittingsuk on eBay.

[Andy1912]

Yes that is the one, thanks for the pointer.

[anonymous-user]

Andy1912 said:

Yes that is the one, thanks for the pointer.

I don't like the standard 'disc' one, it just doesn't seem right. Another option is to buy a spade terminal that has both a male and female part to it. Slide the female part over the disc then connect the wire to the male part. Not perfect but if you do this you can put some heat shrinkable tubing down the whole thing and hold it tightly in position.