v6 engine temp issues
 

The expansion tank cap 'lets go' and squeezes coolant out after long, higher speed journeys. I have replaced the cap with a decent, BMW one (febi) and then replaced it again. I have also replaced the thermostat housing and radiator.
So - I fitted an aftermarket temp sensor in the top radiator hose because of (what I thought) was overheating issues.
Using the onboard diagnostics, the engine seems to run at a temperature of around 88 to 91 degrees, but the top hose aftermarket sensor shows a temperature of somewhere between 100 and 105 degrees.
So; should the top hose be hotter than the engine block? Why is the pressure in the expansion tank causing the cap to leak?
There is no evidence of head gasket failure (mayonnaise etc.) Could it be an airlock? Any thoughts or suggestions gratefully welcome

I would agree with an airlock, 90% of temperature issues on the V6 are caused by an airlock.

I would suggest you get the car looked at by someone who understands how the V6 cooling system works or as you will have seen by previous threads on the V6 you will be going round and round in circles

If you want I'm long way off but you are welcome to bring it here for me to look at

Dave

Hello Andy,

When you did the work on the cooling system, did you refill and bleed it strictly according to the MG Rover procedure for the V6?

Your expansion tank caps are probably working correctly if there's an air lock as Trikey has already said, or if the level is above the 'Max' marker.

Your instrument pack diagnostics reading of 88 - 91˚ is, if anything, on the cool side but perhaps you have unknowingly fitted an 82˚thermostat which other members suspect are on the market (it should be 88˚ giving a running temperature in the low nineties). If you still have the original I would consider putting it back.

The first thing to do is drain the system fully, including the cylinder block plug, and refill from scratch making sure that you raise the expansion tank and don't start the engine until the bleeding process is complete and the screw reinserted. Please let us know if that does the trick.

Simon

Hello Andy,

I am having having temp issues with my Rover V6 too ever since it came back from the garage. The issue is still ongoing, and I have written to the MD of that former Rover garage, waiting to hear back (if I do). They refuse to believe that engine coolant temp runs in the 100s and keep saying that the temp gauge on dash reads Normal!! Yesterday it reached 106°C. Garage is pretty stupid (or think that I am) and will not entertain switching on the odometer trip diagnostic, which shows real time temps. The fans do come on when they should, but the point remains that fan should not be triggered in a short, local journey.

Few businesses seem to have any self-respect.

Did you manage to establish that the coolant temperature sender unit wasn't faulty and eliminate it as the cause of the problem after the garage highlighted it ? A item costing about a tenner from dmgrs
I read the issue's with the use of the T4 but to a competent person with the right equipment a T 4 would not be required to diagnose a faulty temp sender (using the on board diagnostics) against real coolant temperature :shrug:

Hi Steve,

We are not pursuing any further fault-finding until Lida has given the garage's MD an opportunity to respond to her written complaints since this could jeopardise any proposed corrective action.

At present the evidence points to the thermostat since the bottom radiator hose remains tepid. I therefore don't suspect the coolant temperature sender. The garage's technique for diagnosing this, measuring the coolant temperature in an open expansion tank with the engine stopped and cooled down, is unsound.

Simon

The temp gauge does not move off normal for any temperature between 75 and 115!

Talking about a chocolate teapot!!

Apart from what all the others have said, a tell tale sign of a clocked radiator is overheating at higher speed.
These radiators are old by now, and the engine sheds a lot of rust and grit! It could well be blocked badly!

I would give it a flush with emphasis on back flow. Use a light coloured bucket where the coolant comes out and check for foreign matter!

You could be surprised