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300 Tdi temp problems


Ivan
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Also posted in the Defender forum but posted here for a wider audience.

Have mentioned this before but think it was on the old place. Earlier this year I fitted a 300 Tdi to the 90 (was 2.5 Td). The temp gauge would not work with the new engine so I fitted a Racetech gauage and sender. Problem is that the engine appears to be running hot. The gauge shows the temp rising to the 100 mark. I replaced the thermostat, no change. I took the centre of the thermostat out and it was all fine. It never got hot and the highest it ever got to was just under 90 after a long run and then being sat in traffic for 30 mins. Now that winter is here the wife was complaining that it never got warm and the heater was putting out luke warm air (temp gauge never rose much above 40). So, I fitted a new thermostat. Car warms up great but the temp now rises to 100 again and it will go higher if you push it. I fitted a temperature probe into the header tank and took the car for a drive. The temp probe was showing 84 whilst the gauge was showing 100. So I fitted a new sender (from racetech). The gauge still shows the temp rising to 100 and over.

I did suspect the thermostat was not opening properly but I have just fitted another brand new one and am having the same problem. My only possible thought is that the water pump is not moving the water fast enough does this sound feasible ?

Anyone got any clues or ideas as to what's going on ?

Thnx

Ivan

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1st of all check u have a good earth for the gauge and the engine. 84 degrees is about right for a Tdi in town traffic, should never go past 90 degrees even on the motorway. If the heater isn't hot it sort of proves its more a electrical problem. U did use the Racetech sender unit didn't u? The sender is ALWAYS matched to the gauge...

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Simon and John

Thanks for the replies it's given me a couple of things to think about. Yes it was a racetech sender that was purchased with the gauge, as is the new one. When it's reading hot I can put my hand on the top hose (not for too long obviously) and the heater is still blowing hot air (i.e. it's not blowing cold which is the usual sign of overheating). So I'll check the earth to the gauge and also check the wire from the sender. One thing I didn't mention was that I am still using the old TD header tank, so I'm going to swap that for a Tdi version (see classifieds).

Cheers

Ivan

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From my own investigations I've got a 300Tdi water pump you can borrow to try if it'll help? Someone mentioned that the impeller can begin to turn on the shaft (internally) so I tried another one, before I fitted the gauge.

Interestingly, 6 months down the line I'm having trouble getting my engine up to temperature now - maybe I've still got an underlying problem, maybe it's just winter...

The 60degree guide is for the hottest pipe you can actually hold your hand on continuously, ie for 30secs or more. Above that it starts to really hurt...

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John

Thanks very much for the offer, it's very kind of you. I'll test out some theories first this weekend. If that fails I'll let you know and we can arrange for me to try out your water pump. I've also sent you a pm with my contact details.

Thnx

Ivan

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Simon and John

Thanks for the replies it's given me a couple of things to think about. Yes it was a racetech sender that was purchased with the gauge, as is the new one. When it's reading hot I can put my hand on the top hose (not for too long obviously) and the heater is still blowing hot air (i.e. it's not blowing cold which is the usual sign of overheating). So I'll check the earth to the gauge and also check the wire from the sender. One thing I didn't mention was that I am still using the old TD header tank, so I'm going to swap that for a Tdi version (see classifieds).

Cheers

Ivan

Ivan,

I'm still using the TD header tank on my 300 with no problem.

What I think will make a big difference to your cooling is a new pump. I changed mine last week and the needle on the gauge now sits 2mm below half-way instead of 2mm over.

Your troubles do sound electrical to me, I hope you sort them easily.

Mo

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1st of all check u have a good earth for the gauge and the engine. 84 degrees is about right for a Tdi in town traffic, should never go past 90 degrees even on the motorway. If the heater isn't hot it sort of proves its more a electrical problem. U did use the Racetech sender unit didn't u? The sender is ALWAYS matched to the gauge...

Hmmm, the t/stat is rated at 88*C, and should open between 85-89*, so how could it operate colder ??

According to my (VDO mechanical ) gauge I can see it open at roughly 90*, it spikes a little, then modulate around the 90-92* mark, with normal running of 90-96*.

It went close to 100* the other day, I was fully loaded, it was 37*C ambient and I was climbing a ridge.

I'm not worried at all running in this range.

Ivan, it isn't a good idea to run any engine without a t/stat, and particularly not a diesel. most engines rely on a certain amount of restriction/back pressure from the t/stat for proper coolant flow throw the block and head. Take the t/stat out and there is a risk that the coolant can bypass some areas. Not good. The other thing is that the engine components, eg pistons, rings etc, never get hot enough to run at the clearances thay were designed to run at, leading to too much blow by, premature wear, etc.

Edited by rick
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Hmmm, it got down to -5* here a few times last winter here, yet the thing still ran at 90-92*. Admittedly, it was above 0 pretty soon after sun up, and usually somewhere between 8 and 16* during the day, but then, thats a summers day for you blokes, isn't it... :P .

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OK after a weekend of messing about with temperature probes etc (including fitting a new gauge, rewiring the sender) I am pretty sure it's down to an electrical problem. Took the car for a run and the gauge went up to 100 as usual. Checked the header tank when I got back and it's reading 84 ish (gauge still reads over 90 almost 100). Hoses all felt ok. With the ignition and engine off on I caught the indicator stalk and the temp rose and fell by 3 degrees as the indicators went on and off. Put the heater blower on and it rose by another 3 degrees. So I checked the voltage at the sender and it's fluctuating when the indicators are on. By this time it was getting too cold to work outside so gave it up for now. Next task is to check the alternator and charging system to find out why the voltage isn't regular. Is there a voltage regulator on the 90 gauges like on the series vehicles ?

Anyway a big thanks to all forum members for their help and advice, especially Richard (Turbo Charger) for offering to lend me a water pump.

Ivan

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OK after a weekend of messing about with temperature probes etc (including fitting a new gauge, rewiring the sender) I am pretty sure it's down to an electrical problem. Took the car for a run and the gauge went up to 100 as usual. Checked the header tank when I got back and it's reading 84 ish (gauge still reads over 90 almost 100). Hoses all felt ok. With the ignition and engine off on I caught the indicator stalk and the temp rose and fell by 3 degrees as the indicators went on and off. Put the heater blower on and it rose by another 3 degrees. So I checked the voltage at the sender and it's fluctuating when the indicators are on. By this time it was getting too cold to work outside so gave it up for now. Next task is to check the alternator and charging system to find out why the voltage isn't regular. Is there a voltage regulator on the 90 gauges like on the series vehicles ?

Anyway a big thanks to all forum members for their help and advice, especially Richard (Turbo Charger) for offering to lend me a water pump.

Ivan

Check the battery (negative) to body earth, and then body to engine earth wire. The bolts or connectors may have become rusty.

Alternatively, put a second earth wire between the battery and body, then battery and engine.

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Anyway a big thanks to all forum members for their help and advice, especially Richard (Turbo Charger) for offering to lend me a water pump.

It's John, but you're welcome. Is the problem that the +ve is actually fluctuating (relative the battery negative), or that the earth voltage is being dragged up by heavy load/poor connection?

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John

Apologies for getting the name wrong. Not sure as thats the next thing to check. I'll try earthing the test meter to the battery and see if it still fluctuates. I tried it using the earth in the instruments and then earthing to the instrument housing and the voltage reading fluctuated both times. I checked the alternator and the output was fairly constant on tickover.

Rgds

Ivan

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