Thanks Ron. TGM has already done this.

 

Sorry LG if you have mentioned it but i see nothing about replacing the water pump?

If your car is overheating during higher revs and fine at idle then to me this would suggest either a failing radiator or a knackered waterpump not circulating enough coolant around the engine. I would change the pump if you havent before thinking about taking the head off etc.

 

Could be right there, if they use plastic impellers one may have fell off

 

It's not GM/FPT crap! It uses a chopper from a Kitchen Aid:



Ian's problem could be it - sucking in air & then causing inflation.

Good luck finding the bugger - I've resorted to changing every hose, in the days when cars didn't have half-a-thousand of the things.

 

My old HR-V did this ..... exactly the same symptoms. After it had a new HG and pressure tested head it was no better .... i sold the car a few weeks later so never got to the bottom of it.

 

Nick, I've seen cavitation etch pressed steel impellers like that down to virtually nothing before! Very unusual though.

Groover, reading through the above a good bleed seems to have fixed it now; correct?

If you're still having problems pm me or let me know and I can give you a bell and talk it through with you

 

Thanks for that. I think the bleed is a temporary fix. There is definitely something not right as air is getting in from somewhere, particularly if the car is driven hard. I know that if I took it on a track day, the problem would return in a big way.

I'll keep my OBD/Torque combination running to keep an eye on things and drive gently until I can get it looked at more closely.

 

I know the tests say it isn't head gasket but my gut feeling is it may be a minor leak.
Air is getting in. Coolant system is above ambient pressure. Therefore whatever is getting air in has to be above ambient. That essentially boils down to combustion gasses.
I'll keep mulling it over though since the tests are throwing doubt on that conclusion.

 

LG, yup, that's what I did with mine. Kiwi and Torque and BIG gauge to keep an eye on things. The stat on these is set at 89 degrees as standard. THe first fan is at, IIRC, about 92 and the second at 97.

If it gets past about 98, you need to start taking defensive action.

If this happens while driving at ,more than about 40mph, pull over and stop, cos you are out of coolant!

If you are going slow in traffic, you can usually get away with it by gently raising the engine revs to about 2,0000 rpm. This will get the coolant flowing more effectively around the engine and *should* start to bring the temp down a little.

The next step is to pop the heater on max heat, max flow and open the windows. This will increase the "radiator" capacity by something like 25%.

If neither of these help, you are going to need to stop, turn off and let it cool down before you top it up again with more coolant/water. The worst mine did on the day before it went to the garage was 2.5L, so I'd keep a couple of 2L pop bottles in the boot. Water is kinda OK, but in addition to its antifreeze properties, real coolant will boil at a higher temp than 100 degrees, so it you're not afraid of the cost, go with that.

I would stress though that in any case, if your temp gets past about 105, your oil is going to be not doing much to protect things, so you need to stop and turn off. Once you do get going again, if it's had a real overheat (over 105 for more than a few seconds) then you're going to want to do an oil change. Past about 108, even with real coolant, you're now running on a steam/water mix and bad things are going to be happening in terms of pressure where it shouldn't be. Think gaskets (various), hot spots on cylinders, etc etc.

Final horror story is low coolant level can lead to hot spots around the cylinders or the head, which in turn lead to expansion and potentially warped head or increased wear on components. It is very unlikely that you will actually MELT anything, but you can certainly f@#k things up by running with very low coolant.

The above is a guide to limping along, developed over YEARS of driving a V8 land rover in silly places where calling the AA is not an option. Just don't ask...

Coolant shouldn't leak. Unless it's a Land Rover, in which case it's a good sign that there's still coolant in it. You need to get this sorted out mate.

 

This back up what another engineer has told me. I'm making investigations into a gasket change - will the head need a light skim as well?