K series overheating (Jock7s cross post)

Chucks · Post by **Chucks** » Fri May 20, 2011 12:58 pm

Took the ankle biter out for the first run of the season yesterday. All seemed to be fine until stopped in rush hour traffic. Expansion cap went pop, huge clouds of steam & water temperature off the scale. Cue a long & embarrasing wait for the AA.

Topped it up with 1 litre coolant today & ran it up. Can't see any obvious leaks other than whats come from the cap & given the amount of coolant I dumped on the road / engine bay yesterday I suspect that 1 litre was all lost at the time the cap popped. Fan & thermostat are both working but when idling the temperature seems to regulate between 100 & 120 where in the past it didn't go much above 80deg. Next step will be a block test to see if the head gasket has survived. If the head gasket is gone it won't be clear whether thats the cause or effect of the overheating. Anyone got any thoughts?

Cheers

Charlie

Oh & cheers to Colin for saying fit like as I was waiting for recovery. Could tell by the look on your face you feel my pain.

Dominic · Post by **Dominic** » Fri May 20, 2011 1:03 pm

Easy answer, but sounds like HGF to me. I know it's a totally different beast, but same principle; last summer when I was having HGF problems with the landrover, one of the symptoms was the cooling system becoming highly pressurised; blew the header tank, then the radiator. Cylinder pressure leaking into the cooling system. Just my 2p, but then again, I know very little about such matters so don't pay too much attention!

eoinmac · Post by **eoinmac** » Fri May 20, 2011 1:20 pm

Charlie ..mine did exactly that after being left for 3 mths in the cold weather

Did as you did and filled with coolant and have had no problems ! I think it must have been an air lock after lying idle for so long

Chucks · Post by **Chucks** » Fri May 20, 2011 2:43 pm

Ok further investigation reveals the cause to be a bad electrical connection to the fan. It was only kicking in intermittantly. Ran it up a second time today & the temperature went past 100deg without the fan kicking in. Fiddle with the connection & it's now working & regulating water temp between 80 & 90 deg.

Weird as first time I ran the car today the fan was definately kicking in. Possibly just not getting enough electrical oomph to be turning full speed.

I'll give the contacts a clean up but next question is how to test to make sure I'm getting a consistently good connection. Should I be checking amps, volts, resistance??

Tried running a block test to check the head gasket with one of these
http://www.uktools.com/block-tester-p-12508.html

Anyone used one before? I'm not having much joy, just seem to keep sucking coolant into the tester. I'll try draining off the header tank a bit but anyone got any other tips?

Cheers

Charlie

robin · Post by **robin** » Sat May 21, 2011 10:34 am

Does your fan run from a rad-mounted temperature switch or does it run under ECU control via a relay (which is the normal way for K-series engines, but I don't know what Caterham do).

Cheers,
Robin

Chucks · Post by **Chucks** » Sat May 21, 2011 11:44 am

Hi Robin,
The fan runs off a rad mounted switch. I think the route of my problem is the connection from fan to loom.

robin · Post by **robin** » Sat May 21, 2011 2:29 pm

OK, well then you can do a couple of tests.

(1) Heat the car up so the fan should be running. Remove the two wires from the rad switch and measure the resistance across the terminals. If there is only one wire, measure the resistance from the one wire to the battery -ve terminal. In either case it should be very low (<0.5 ohms). Some multi-meters struggle to measure low resistances accurately; to improve accuracy touch the probes together and see what it reads. If it reads 0.2 ohms, say, then you should subtract that from your switch reading.

(2) Now you can turn off the engine, but turn the ignition back on again. Measure the voltage on each of the two wires with the red probe connected to the wire and black probe connected to the battery negative terminal. My guess is that one wire will measure +12 the other 0v. For the wire that measures +12v measure the resistance from the wire to the battery +ve terminal. Also measure the resistance from the wire that measure 0v to the battery -ve terminal. One or other of these will be a very low reading (again, <0.5 ohms). The other could be as much as 10ohms. If both are very low, that's still OK. If one is a lot higher than 10 ohms, that's your problem.

(3) Reconnect the wires to the rad switch. Now pop the wires off the fan and measure the resistance of the fan (again if it has just one wire, measure from the terminal to the battery -ve). If the fan reistance is high (>10 ohms) then the fan is probably bust. If the fan resistance is a lot lower than the higher of the resistances you measured before then you have a dodgy contact or burnt wire somewhere in the circuit from the fan to the rad switch or the battery.

Post what you find and we'll dig deeper.

Cheers,
Robin

Chucks · Post by **Chucks** » Sat May 21, 2011 4:35 pm

Cheers Robin, much appreciated.
Had a call this morning to offshore tomorrow so further diagnosis will have to wait for now. Ran the car out to its garage today & it was working fine albeit I wasnt stuck in traffic for any length of time. Hopefully I'll have got away without doing it any damage.

robin · Post by **robin** » Sat May 21, 2011 5:17 pm

125 is the limit beyond which damage is likely. Brief periods at 120 probably won't do any damage.

Cheers,
Robin

Scottish Elises

K series overheating (Jock7s cross post)

K series overheating (Jock7s cross post)

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