K-series running too hot - how to test the radiator fan?
Discussion
Afternoon all,
Having taken the engine/gearbox out I'm not ready to get the old girl back on the road.
Having put it all back to together I'm having an issue with the car running hot - k-series engine.
At idle the car is running hotter than it used to - it will work its way up to about 100 degrees and then stay there (before I shut it down).
I'm convinced that I now have most of the coolant back in - about 4.5 ltrs. Is there much more to go in? Do I have an airlock somewhere?
Also the lower rad/hoses are not getting hot - is the themostat not opening up?
Finally I've also noticed that at the radiator fan doesn't kick in either even at 100.. is there a way to over ride this to check that it's actually working?
Sorry for so many question, but it's annoying really; this car has always held perfect temperature whatever the conditions and even when left to idle after a session on a hot track day the needle rarely moves.. Knew I shouldn't have meddled...
Any ideas?
Having taken the engine/gearbox out I'm not ready to get the old girl back on the road.
Having put it all back to together I'm having an issue with the car running hot - k-series engine.
At idle the car is running hotter than it used to - it will work its way up to about 100 degrees and then stay there (before I shut it down).
I'm convinced that I now have most of the coolant back in - about 4.5 ltrs. Is there much more to go in? Do I have an airlock somewhere?
Also the lower rad/hoses are not getting hot - is the themostat not opening up?
Finally I've also noticed that at the radiator fan doesn't kick in either even at 100.. is there a way to over ride this to check that it's actually working?
Sorry for so many question, but it's annoying really; this car has always held perfect temperature whatever the conditions and even when left to idle after a session on a hot track day the needle rarely moves.. Knew I shouldn't have meddled...
Any ideas?
Really new to the K-Series so I had a look in the build manual - it's does say to remove the heater hoses and backfill them with coolant. It then goes on to say to Jack the back of the car up as high as possible as it should assist in bleeding (at operating temp) and prevent airlocks (from experience on other cars a cool bottom hose is a symptom of this).
I'm sure others with loads more experience than me will chime in but I'm just passing on what I've read recently.
I'm sure others with loads more experience than me will chime in but I'm just passing on what I've read recently.
Do you have a bleed valve at the top of the radiator - loosen it and see if coolant comes out to make sure there isn't air at the top of the radiator.
Have you checked the fuse for the fan?
Depending on how the rad fan is wired you may be able to test it very simply. If it is a temp switch in the rad then you may be able to take out the connector on the back of the switch and short the terminals, this should switch the fan on.
Alternatively if it is ECU controlled you'd need to plug it in to see what temperature the ECU is seeing (ECU temp sensor is usually separate from the one used to feed dash gauge).
However, if the bottom hose is cold I'd suspect a thermostat or pump issue.
Have you checked the fuse for the fan?
Depending on how the rad fan is wired you may be able to test it very simply. If it is a temp switch in the rad then you may be able to take out the connector on the back of the switch and short the terminals, this should switch the fan on.
Alternatively if it is ECU controlled you'd need to plug it in to see what temperature the ECU is seeing (ECU temp sensor is usually separate from the one used to feed dash gauge).
However, if the bottom hose is cold I'd suspect a thermostat or pump issue.
Edited by GreigM on Thursday 17th July 19:29
Ah yes, the classic issue of refilling the K series coolant circuit 
I'd bet my house you have an airlock in the system, in fact when I had my engine and gearbox out over the winter I had the exact symptoms you do. First up you can test the fan by having the car running and shorting the two terminals on the rad sensor that goes to the fan. That'll prove that works.
The best way to fill the coolant back in (and I believe the amount is just over 5 litres) is to start at the top radiator hose. Unclip it from the rad and turn it through 90 degrees so it's sticking upwards. Next open the heater valve fill it until it gets to the top, quickly refitting it to the rad when it does. Then, fill from the expansion tank, this means both sides of the thermostat are filled. Remember not to rush filling both sides though, literally trickle it in to allow the air to escape. Then, massage the lower rad hoses aggressively to get rid of the air bubbles. It also does help to have the car jacked up slightly too to bleed from the rad top as a final stage.
Hope that helps, although it's not critical I've got a bleed tee fitted in mine and it really does help to get all the air out, even though on mine I don't have a heater fitted.
I'd bet my house you have an airlock in the system, in fact when I had my engine and gearbox out over the winter I had the exact symptoms you do. First up you can test the fan by having the car running and shorting the two terminals on the rad sensor that goes to the fan. That'll prove that works.
The best way to fill the coolant back in (and I believe the amount is just over 5 litres) is to start at the top radiator hose. Unclip it from the rad and turn it through 90 degrees so it's sticking upwards. Next open the heater valve fill it until it gets to the top, quickly refitting it to the rad when it does. Then, fill from the expansion tank, this means both sides of the thermostat are filled. Remember not to rush filling both sides though, literally trickle it in to allow the air to escape. Then, massage the lower rad hoses aggressively to get rid of the air bubbles. It also does help to have the car jacked up slightly too to bleed from the rad top as a final stage.
Hope that helps, although it's not critical I've got a bleed tee fitted in mine and it really does help to get all the air out, even though on mine I don't have a heater fitted.
Most certainly an airlock as stated. Right pain in the arse, but a right of K Series passage!
I found filling the coolant header tank a little, then squeezing and wriggling the bottom hose going to the heater and the hose coming from the block/ thermostat housing, then adding some more liquid, doing the same really going mad. Keep going. You should hear gulps of air coming back up to the header tank.
Once you've done a successful fill, you'll be used to the rigmarole. Just dumping water into the tank all at once will keep you working for hours!
I found filling the coolant header tank a little, then squeezing and wriggling the bottom hose going to the heater and the hose coming from the block/ thermostat housing, then adding some more liquid, doing the same really going mad. Keep going. You should hear gulps of air coming back up to the header tank.
Once you've done a successful fill, you'll be used to the rigmarole. Just dumping water into the tank all at once will keep you working for hours!
My engien temp reported by the Stack hits 104 deg when sitting in traffic - It did 2 hours queuing to get into Classic LM and didn't exceed 105.
There is of course the question as to whether its using a Caebont or Stack sender - the linearity of whihc are unlikely to be the same, but that aside it gave the same readings with the R300 engine. TBH I thing its unlikely Caterham paid for the Stanck sensors.
Fan cuts in (its on a switch, not ECU driven) at about 98deg. Normal running on the open road is 78 degress (ish).
What do others running a Stack get?
There is of course the question as to whether its using a Caebont or Stack sender - the linearity of whihc are unlikely to be the same, but that aside it gave the same readings with the R300 engine. TBH I thing its unlikely Caterham paid for the Stanck sensors.
Fan cuts in (its on a switch, not ECU driven) at about 98deg. Normal running on the open road is 78 degress (ish).
What do others running a Stack get?
I recently binned my standard VDO temp gauge on my 1.4 K series Roadsport, and fitted a stepper motor Stack gauge. The car will run up to 102 degrees before the fan kicks in, but it never goes passed this.
A winter mod I have in mind, is to remove the inlet manifold, and drill out the dreaded tickle valve, and put a restrictor in the bleed off pipe, so that there is continuous bleed from the inlet manifold, to the header tank. I am also going to put a similarly restricted bleed in the top of the rad, back to the header tank. I have already drilled a 2.5mm hole in the thermo-stat.
On rebuild I will fit one of the Viton gaskets to the manifold, to hopefully prevent any issues in the future.
Going off what someone posted in another thread, the VDO oil pressure gauge got binned aswell.
A winter mod I have in mind, is to remove the inlet manifold, and drill out the dreaded tickle valve, and put a restrictor in the bleed off pipe, so that there is continuous bleed from the inlet manifold, to the header tank. I am also going to put a similarly restricted bleed in the top of the rad, back to the header tank. I have already drilled a 2.5mm hole in the thermo-stat.
On rebuild I will fit one of the Viton gaskets to the manifold, to hopefully prevent any issues in the future.
Going off what someone posted in another thread, the VDO oil pressure gauge got binned aswell.
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