Hot air fine when moving, but cool stationary?

[Fred Pitt]

Originally Posted by SD1too

That's a good point Glenn particularly as there's evidence that the thermostat is also suffering from the effects of the "some kind of rad fix solution", probably K-Seal.

Hmmm, that's around 10° too cool so your thermostat has probably been sealed in a partial or fully open position. Your going to need several flushes using a cleaning agent and another new thermostat which should all be at the garage's expense, not yours.

Simon

Im sorry, I missed a step in my explanation.
They fixed a leak from the straight plastic pipe and during this I think they used some sort of rad seal. A few days later I checked in my expansion tank and saw tiny glittery bits floating around in there, that were NOT there before I took it in. I took it back and questioned him and he said he didn't use any sort or rad seal. He has always been honest before, have used him for years. Not wanting an argument, I asked him to empty the coolant, flush out my matrix and refill with new coolant. He done this according to him. The coolant was definitely changed as I inspected it. It's since then I have noticed the above problem. I assumed an air lock of sorts. I may ask to have another empty, flush, refill cycle but need to find a mechanic that is savvy with rover kv6 procedures.
I'm not concerned with the stat. It had a new one 9 months ago, and my car has always run at 81° since I bought it a year ago. I've become so hung up on it overheating I fitted an one reader so I know it's accurate. I learnt within weeks of owning the car to ignore the dash temp gauge

[thanos.m]

Just a couple of pointers from me besides an airlock.

If you suspect that some sort of radweld was used the Rover 75 heater matrix is known to be prone to blockages so one thing to check is have your heat on and feel with your hand then temperature of the air and move from the drivers side to the passengers If the air is getting progressively colder towards the passenger side your heater matrix will most likely be blocked.

Also I'll agree with Simon your car seems to be running cold it should be around 95C° I've had a similar problem and I think a few members of the forum have pointed out that replacement thermostats as of late seem to make cars run cold. I went through 3 thermostat last year because I had a cold running issue. The second one made my car run at about 78-82C° similar to yours and my heater performance was appalling.

[vitesse]

You're quite right about the new thermostats. Mat confirmed that he can't get hold of the original spec 88 deg ones, and only has the cooler ones now. I've got an order in with him at the moment for a set of new O rings for the thermostat system and have removed a genuine 88 deg used thermostat from my donor rather than buy one of these low temperature ones.

It might not matter too much in the UK climate but here a low temperature thermostat is for summer use only.

Actually the O rings from the donor thermostat looked like new, not compressed and I could probably have reused them.

Regards

[Fred Pitt]

Originally Posted by thanos.m

Just a couple of pointers from me besides an airlock.

If you suspect that's some sort of radweld was used the Rover 75 heater matrix is known to be prone to blockages so one thing to check is have you heat on and feel with your hand then temperature of the air and move from the drivers side to the passengers If the air is getting progressively colder towards the passenger side your heater matrix will most likely be blocked.

Also I'll agree with Simon your car seems to be running cold it should be around 95C° I've had a similar problem and I think a few members of the forum have pointed out that replacement thermostats as of late seem to make cars run cold. I went through 3 thermostat last year because I had a cold running issue. The second one made my car run at about 78-82C° similar to yours and my heater performance was appalling.

I understand it's a bit cool, but 95 seems worryingly high to me.
Traffic here in great Yarmouth is dreadful at 9 and 16:00, and if I was driving my 75 at around 95, it would continuously be tripping the cooling fan when I stop at lights. I've learnt this isn't really the car to be sitting in traffic with.

[SD1too]

Originally Posted by Firmus Piett

... I checked in my expansion tank and saw tiny glittery bits floating around in there ... he said he didn't use any sort or rad seal.

Other members have described the "tiny glittery bits" in the expansion tank after K-Seal has been administered. You would certainly see no such thing if your cooling system was filled with just water and antifreeze.

Originally Posted by Firmus Piett

... my car has always run at 81° ... I fitted an one reader so I know it's accurate.

I don't know what a "one reader" is Darren but I'd strongly recommend that you check its accuracy by activating the instrument pack diagnostics which gives a digital display of the coolant temperature sensor's output.

Originally Posted by Firmus Piett

I understand it's a bit cool, but 95 seems worryingly high to me.

Rest assured that it isn't. Your engine is designed to run at temperatures up to 100˚ before the radiator fan is triggered.

Originally Posted by Firmus Piett

Traffic here in Great Yarmouth is dreadful ... it would continuously be tripping the cooling fan when I stop at lights.

You are correct to say Darren that in a sustained traffic queue the cooling fan will be triggered regularly. That is the way that all electric fan systems work because the radiator receives no forced cooling unless the car is moving. Your engine will come to no harm running at temperatures in the low nineties. It was designed to operate in those conditions.

Simon

[Fred Pitt]

Originally Posted by SD1too

Other members have described the "tiny glittery bits" in the expansion tank after K-Seal has been administered. You would certainly see no such thing if your cooling system was filled with just water and antifreeze.

I don't know what a "one reader" is Darren but I'd strongly recommend that you check its accuracy by activating the instrument pack diagnostics which gives a digital display of the coolant temperature sensor's output.

Rest assured that it isn't. Your engine is designed to run at temperatures up to 100˚ before the radiator fan is triggered.

You are correct to say Darren that in a sustained traffic queue the cooling fan will be triggered regularly. That is the way that all electric fan systems work because the radiator receives no forced cooling unless the car is moving. Your engine will come to no harm running at temperatures in the low nineties. It was designed to operate in those conditions.

Simon

That should have said OBD reader.
I have tested it with the onboard diagnostic setting (19/7) and it is identical. I understand the OBD reader just replicates what is being read by the instrument pack anyway.

[xsport]

Originally Posted by slovcan

People who are smarter and more experienced with the 75 than I say an airlock is the likely culprit. Who am I to argue with that? They're probably correct.

The one other thing that comes to mind, though, is the possibility that the heater core (matrix) may still be restricted with the remnants of the goop that was put in to fix the original leak. That stuff is just evil. Some heater cores have smaller passages than radiators. I'd be prepared for another flush - maybe even just the core through the heater hoses and with a cleaning agent or vinegar or something. If the drain/refill process doesn't do the job...

Good luck,
Glenn

agree. sounds like there is barely a dribble going through the heater matrix on tickover . once engine speed increases so does the pressure from the waterpump ... hence more heat. it could also have as trikey says an airlock to compound the issue yet further,

[suzublu]

If you're sitting in traffic and the temp starts rising, press the demist button, it turns the fan on Have a look for a digital temp guage, a chap called Harry used to sell them on ebay Here's mine

[Fred Pitt]

Originally Posted by suzublu

If you're sitting in traffic and the temp starts rising, press the demist button, it turns the fan on Have a look for a digital temp guage, a chap called Harry used to sell them on ebay Here's mine

Yeah I use that trick all the while, and I have an OBD reader permanently attached and on my dashboard so I can always see my ECT. It's crazy how quick it goes from 82 to 90 when just stopping at lights.

[Andy_with_a_screwdriver]

Originally Posted by suzublu

If you're sitting in traffic and the temp starts rising, press the demist button, it turns the fan on Have a look for a digital temp guage, a chap called Harry used to sell them on ebay Here's mine

Likewise the 'econ' button does the same without redirecting the air to the vents.