k overheating or is it

[gavingraysonr300]

Im at my wits end with this. car runs around 85deg when stationary creeps up to 95deg fan comes on but sometimes i will stop at the lights and it will creep up to the 100 mark or slightly more no fan but then sometime might come on and cools down. ive put new fan switch, sensor on and had a new thermostat not so long ago. i think ive got rid off all air locks as thermostat seams to open when i let it tick over in garage and fan comes on and off seams to be when i go out in the car for a long run. could it be the gauge or sensor for the gauge at fault. also when i came back off a run today noticed the expansion tank was quite high when i went out it was between min and max is it a faulty expansion cap that is causing it. 

[Jonathan Kay]

What's the nominal opening temperature of the thermostat? Have you had it out and checked that it's opening?

What coolant is in there?

... and it will creep up to the 100 mark or slightly more no fan

When that happens short out the fan sensor... does it come on?

Is the fan blowing in the correct direction?

... also when i came back off a run today noticed the expansion tank was quite high when i went out it was between min and max is it a faulty expansion cap that is causing it. 

Is it the original cap?

What's the level in the tank when cold?

Jonathan

[gavingraysonr300]

comma x stream G30

how do you short out the fan sensor bridge it 

i presume the fan runs in the correct direction as it does cool down when it comes on how can you reverse it any way 

yes it is the original cap

level in tank between max and min

[gavingraysonr300]

think the thermostat opening is 82deg and yes i did test it before i put it in and drilled the hole in it to allow air bubble to pass 

 

[Jonathan Kay]

how do you short out the fan sensor bridge it 

Yes.

i presume the fan runs in the correct direction as it does cool down when it comes on how can you reverse it any way 

Connect the wires to the motor the other way round...

Jonathan

[gavingraysonr300]

i will check the fan wires but i can usually here the fan coming on so when it creeps up to the 100 or above im listening for it i feel it needs to kick in earlier. so why does it kick in sometimes but not always it it that the thermostat is shutting i would of thought on a long run it would be open all the time ?

[Jonathan Kay]

Don't know. But there are two* different causes of the fan working sometimes but not always when it should... and shorting out the sensor when that occurs should help to work out which it is...

Jonathan

* At least.

[gavingraysonr300]

if it dosnt come on what does that mean

[Jonathan Kay]

Assuming that it's hot enough (where the sensor is) that the fan should be on but isn't:

1. If it then comes on when you short the sensor then the sensor might be intermittently failing.
2. If it doesn't then there might be an intermittent problem with the motor or the wiring.

Do you have a multimeter?

Jonathan

[gavingraysonr300]

yes

 

[gavingraysonr300]

it is a new sensor 

[CycleSi]

I've had a similar problem recently which was caused by air in the system which meant the radiator wasn't always getting as hot as it should have been but the rest of the system was cooking. This is turn meant the fan didn't always come on so the coolant tank boiled over.

Initially l thought it was a stuck or failed thermostat, so replaced that, but after 3 abandoned track days, much swearing and even more frustration, discovered it was head gasket failure in 2 places which was causing air to be drawn into the system.

Replaced the HG with a Payen BW750 & new head bolts and everything has been fine since.

[SM25T]

Have you got a bleed bolt in the top of the radiator .... remove it when system cold and pressure has been released. If header tank of rad is not full of coolant ... fan switch will not operate correctly. Replace expansion bottle cap .... they do fail. Check the little ball valve in the cylinder head (if a k-series) is still opening. It is inside the spigot of the little hose that connects to the top of the expansion tank. Poke inside spigot with a screwdriver and tap the ball to unstick it. Some have removed it. It allows air out of the head to flow to the bottle.

[SM25T]

With the heater open ... are all the hoses getting equally hot ? If not ... It is an airlock.

[gavingraysonr300]

How did you find out it was the head gasket can you test it somehow or do you have to take the head off to check ?

 

[gavingraysonr300]

thanks for the advise how do you know if the cap is working correctly and if its not will it cause this problem ? i have taken the bolt out twice and had to top the top of the radiator up but where does it keep going.

[CycleSi]

Apparently you can do a "sniff test" - Google it.

l didn't bother as the evidence/symptoms pointed towards the HG so l had the head removed and sure enough the HG had gone in two places. Probably best to do the sniff test first though l guess.

[jrgibb72]

Hi,

This may be not help, my experience of the K is from my Elise. HGF externally is typically between pot 3&4  so on the Caterham towards the front on the right as you look at the car above the exhaust manifold. Internally you'll see either a rise in the water level in expansion tank if it blowing into the water system or a loss of coolant and viscosity in the oil if it's water into the oil, smell and feel between the fingers will give you an indication of this.

Hard water pipes will also indicate HGF when it's up to temp (high pressure in the system).

If you continue to suspect the temp switch for the fan bench test it with a battery, a bulb and some boiling water.

it sounds like an airlock with there being a difference between the temp at the gauge sensor and the fan switch sender - ie it's hot at the gauge sensor thus showing high temp on the gauge but below the fan operating temp elsewhere in the system.

whats the recommended process in the Caterham when changing coolant? You may want to try raising the front of the car to get any air into the rad? 

Id avoid drilling the stat, again if there's any suspicion it's that bench test it in the kitchen in a saucepan and with yr Mrs food temp gauge (when she not around!) 

You may want to try this DIY pressure bleeding process (part way down the page)

http://wiki.seloc.org/a/Bleed_the_cooling_system

Hope this helps!?

Jason

 

[Jonathan Kay]

whats the recommended process in the Caterham when changing coolant?

Apart from changing the circuit, and in addition to the usual, including opening the heater valve, there are supporters of:

1. Angling the car
2. Fitting a bleeding T-piece somewhere high in the circuit, either plastic or metal
3. Massaging* the hoses
4. Drilling a hole in the thermostat (pictures are available).

It's never been clear to me why some suffer and some don't.

Jonathan

* The Nigella Lawson voice is optional.

PS: The relevant information is scattered across a vast number of threads. Wouldn't it be nice if there were a single multiauthor technical wiki with it all one place... ?

[Jonathan Kay]

How did you find out it was the head gasket can you test it somehow or do you have to take the head off to check ?

As above. You might see an emulsion in the engine oil or coolant. There are chemical tests for combustion products in the coolant: either DIY or at a garage.

Jonathan

[Roadsport06]

First thing for me would be to fit a bleed tee in the top heater hose to eliminate air locks as a suspect. Costs little and makes life easier in the future.

If you are really losing coolant then you need to carefully check for a leak. Up on stands is going to be easier to check out better still a friendly garage to go on the lift. Top water rail, radiator seams etc. The expansion cap could be a culprit too.

I had similar symptoms years back, pin hole in a hose was letting coolant out when pressure built up and air in when cooling. It was difficult to track down as once enough coolant had been lost the house wouldn't lose any more coolant so I tracked it after topping up coolant from the bleed tee, idling the car to temperature and then holding the revs higher.

I say this as the cheap and easy things are the ones before moving to HGF.

 

[jrgibb72]

PS: The relevant information is scattered across a vast number of threads. Wouldn't it be nice if there were a single multiauthor technical wiki with it all one place... ?

Totally agree - they are easy to setup in curtain web based products - I run my web sites using WordPress and there are templates for wiki type applications.

I did my own just for links to how to's for the Elise for my own benefit (and a bit of techi curiosity).

My wiki 

 

[mark7]

Been there got the t-shirt... I can understand your frustration.

The head gasket had failed on my 1.8 k-series.  The mode of failure was exhibited by:

1. Driving the car under normal conditions with the engine heating such that the thermostat opened at 88 deg C.

2. As long as the temperature gauge stayed above 80ish everything was fine.

3. I would then start driving a bit quicker, the temperature gauge would drop and I assumed the thermostat closed.

4. The thermostat would subsequently not open (due to an airlock) and then full on overheating, temperature gauge in the red.  On inspection the bottom of the radiator was stone cold whereas the top was baking hot.

To fix it I changed the following things:

1. New radiator from Radtec.

2. 82 deg C thermostat.

3. New cap on expansion bottle.

4. Cooling circuit modification according to September 2012 Low Flying including a bleed valve in the top rail.

5. New head gasket in conjunction with the head being skimmed.

6. Importantly match the fan switch to the thermostat.  I spent a good half hour speaking to the guy on the Radtec stand at the 60th about this.  Mine is 86 to 76 deg C.

The proof is the pudding.  I did the Cadwell track day the day after everything was fixed.  It's been fine since! 

Good Luck

Mark

[jrgibb72]

If you do a head gasket replacement get the SAIC kit - false economy using anything else imho.

Kit here

J

[Gnockoff]

My first impression on reading this would be to check your temperature gauge was in fact operating correctly as the senders are notoriously unreliable. It is after that when you need to go deeper into the problem.