Thread: How hot is HOT!

I can't quite recall the full significance but 121 was a threshold for the TD5 in the D2.

Originally Posted by Graeme

I can't quite recall the full significance but 121 was a threshold for the TD5 in the D2.

coolant under pressure boils about 130??

127 deg is when the TD5 D2 temp gauge needle drops to the bottom and turns on the overheated LED in the gauge. However by that time the head gasket was done and risked a warped head. The WSM dcuments the duty cycle of the temp signal from the ecm for a couple of temps with the highest one at 121. The Bosch temp sensor is only accurate up to 130 deg.

I was recently towing my camper and had my IID tool pluged in to monitor some temps. With flat road travelling the coolant temp was reading high 80s - low 90's. Going up hills I was just cracking 100deg. Engine oil temp around 112 with the higher loads, but that dropped of to mid 90's on the flats

At 119 degC you would have been very much on the border line of going into limp mode. The temp gauge in a modern car is more like a 4 position indicator (cold / warm / normal / too hot). The halfway point represents the car is in the normal allowable range. This will be at least a 30-40 deg band where it does not move. Once it does start moving upwards again then you are into overheat range and need to back off urgently (or the ECU will intervene anyway and go into limp mode).

Of course if you did not have the ScanGuage then you have been oblivious to all of this - which is what the manufacturers want so as not to alarm you to the normal variations you could see.

Now that you do know it was seeing 119, in my opinion this is too high. Sure it did not boil, but there was very little margin remaining. I would be checking you don't have an issue with the cooling system (or back off next time).

Hi All,
Interesting topic Jonesfam and I hope you don't mind but I'd like to investigate this a bit more.
So.... What should people do to by way of preventative measures?
changing the coolant regularly? Given many coolants with anti freeze/boil have 3 year/100 thousand k "Advertised" life expectancy. What do people think is a reasonable time/distance to change the coolant.
What other actions would people suggest Jonesfam do to reduce the temp?
pull the radiator and have it cleaned and pressure tested? I'm not aware of any "in car" radiator cleaning products.
Has anyone replaced their radiator due to old age etc? If so @ how many k's?
Any other ideas/suggestions?

I set-up my home-grown TD5 D2's temp monitor to go full alarm mode at 118 and also close the inlet throttle valve to allow not much more than idle until the coolant temp got back down to 115. It never got to 118 but saw 115 one quite hot day idling along in top gear so dropped a gear to get the revs up for better cooling.

I would also question the accuracy of the tools readout.
I had an early Nannycom on my D2,I used it in instrument mode consistantly.From tome to time it would throw 160degC+ temps for a short time,sometimes -160degC temps.
I put it down to interference on the system,guessing its possible in these newer beasts too.
Andrew