Thread: engine temp

Is the temp you're looking at coolant temp, or head temp?

Coolant temp can definitely get over 100 and my TDI always does if it's a hot day up a freeway hill. Mid 90's around town if it's hot and A/C on. I think anything upto 105 is probably OK, but past that I get very nervous! I'll let someone else comment exactly how hot is safe, but generally anything up to and around 100 is fine.

It's not coolant temp, the temp sensor is mounted under a bolt on the block. Would being bolted to the head give a more accurate reading?

I'm not sure it's more or less accurate - it's different.

TBH I'm not sure what head temp's are OK from a bolt on sensor. I don't have a head bolt sensor.

I have mine bolted to one of the bolts on the thermostat housing.

Dave

Originally Posted by dee1

It's not coolant temp, the temp sensor is mounted under a bolt on the block. Would being bolted to the head give a more accurate reading?

Yes the stock gauge barely moves, and if it does its usually too late to make a difference. I attached mine to one of the thermostat housing bolts, closest to the original sender, and I think of any part in the engine the head would be the hottest, and would reflect the most and any immediate change. Overall all the metal in the engine would get to the same temperature eventually. Mine got to high 90s also last week in the Melbourne furnace with AC on. I have my watchdog warning set at 104 - I think somewhere on one of the posts they said that coolant cavitates at 115, so is set to warn me to back off or stop before getting to that.

I spoke to my head mechanic, who I might add really knows his stuff and I can highly recommend, and he said that running any lower than mid 80's could harm the engine due to running too cool, somewhere between 85 and 95 is standard operating temps for those motors depending on humidity, outside temp, winds, and speed. He also said that damage to the alloy would start to occur at 120-125 depending on several factors such as if the motor had been overheated before etc. He wouldn't start to worry until he hit 105. Remember that whatever temp you start damage control the peak temp will be several degrees hotter. I have two electronic gauges fitted on my disco 300tdi auto here in Perth, (where we regularly see fairly hot days over summer and I live in the hills,) one TM2 fitted to the head on the spare threaded hole beneath No1 glow plug, (alloy conducts heat faster than steel) and a different branded one in my coolant at the thermostat. Both generally run at the same temp but the coolant is quicker to respond to changes i.e. it will rise and fall before the head temp. I see on an average trip through the suburbs around 86-89, pushing to 90-91 on hills. An extended run up Greenmount hill can see me hit 98 on a hot day with me thrashing the motor. I have a new rad, water pump, viscous coupling, thermostat, and Penrite coolant so is as close to new as I can get it! Don't worry if the temps fluctuate a lot as that is just the engine running as it should! I have my TM2 set to 97 but I am paranoid and cool it down long before that! The other gauge switches the aircon fans on at 89. So Dee1 your motor is running beautifully, just make sure you keep the servicing up to it and you (hopefully) will never have a problem! Hope this helps.

Lane

Originally Posted by Judo

I'm not sure it's more or less accurate - it's different.

TBH I'm not sure what head temp's are OK from a bolt on sensor. I don't have a head bolt sensor.

I've got the bolt-on version and my temps - and my thinking about those temps - are the same as Judos. The alarm is set at 106 degrees.

are we assaying that the vehicle gauge is not accurate? reason i ask is today my gauge hit the red out of the blue just after filling up driving along Gt North Hwy. Had to stop 4 times and could only travel a few lays before it would heat back up - coolant level was ok etc, then i opened the cap on the expansion tank a tad it burped a bit and then i drove the rest of the way of home without the gauge moving over half way which was another 25 minutes - go figure...