Rover 75 V6 coolant Temp Weirdness

[Roverageous]

Right, I've just had Dad on the phone who reckons his 75 V6 is still being dodgy.

 

History is that it got a bit warm about 3 weeks ago (110'c) and then he noticed coolant loss. Got it to Mr Garage Man who diagnosed a leaking water pump and thermostat housing. Did the work including cam belts and charged £750 which sounds about right on these.

 

I had a drive of it the day after it was done and all seemed well, apart from the onboard temperature read out was jumping around a bit from 90'c - 98'c. All within the normal range, but it would jump from 91'c to 98'c and back to 94'c within seconds. Now I may be well off the mark here, but I think it's fairly impossible for a system with 5 litres of fluid pumping round it to jump up and down temperatures that quickly?

 

Anyway he's been on the phone tonight because he thinks the water pump isn't working properly. Apparently it's running the high speed fan most of the time, even when at NSL speeds, and the onboard temp display is showing anything from 90'c to 115'c - again jumping around from temp to temp. The biggest jump he's seen from one temp to another was 95'c to 107'c - for a real time read out that's quite a jump!

 

A few things I asked him to check:

• Coolant level is up to MAX
• Top and bottom radiator hoses are getting hot
• Radiator itself is getting hot
• Cabin heater giving off warm / hot air when asked to
• Car does not smell particularly 'warm' after being driven / showing high temps on the read out.

 

For reference my V6 R75 runs between 91'c - 93'c when motoring, and will creep up to 100'c when sitting in traffic but the low speed fan brings it down promptly to 94'c. My readout does not jump between temperatures.

 

I'm wondering whether this is a faulty sensor rather than something still wrong with the cooling system? Sound plausible?

[DodgeRover]

Yes sounds plausible, there's no way to get instantaneous leaps of temperature like that.

 

Fan might be triggered by the dodgy sensor.

[purplebargeken]

I would tend to concur re:temp sensor. 

[gadgetgricey]

Air lock in cooling system??

[AMC Rebel]

Wisdom on the R75 forum was always airlocks - the procedure for filling from empty is insane.

 

If it only runs the fan at high speed that could be the fan resistor preventing the low speed fan from running - mine used to cycle he high speed fan quite a bit when my resistor was buggered. The low speed should run full time on a KV6 when the engine is running if climate is in full auto mode.

[Guest]

Yup, it needs a burp. Was a similar thread from Bobthebeard a while back..

[Bobthebeard]

  On 22/11/2017 at 23:48, Barry Cade. said:

Yup, it needs a burp. Was a similar thread from Bobthebeard a while back..

Mine did indeed require 'burping' .

After a couple of attempts success was achieved. So far anyway. Coolant and temperature levels have stabilised nicely.