This page contains technical odds and ends and experiences that I have found useful.
Too Hot To Handle : engine temperature issues..
As posted on this forum, early 2006 www.nzveedubnuts.com : NZ VW forum
This is a bit of a rant on my experiences in dealing with temperature issues with VW engines.
The traditional way for deciding if your VW motor is running too hot or not is just to grab the dipstick firmly… if is so hot you can’t hold it, then the engine is running too hot. But, you might like to be a bit more scientific than this, and your arm might not be long enough to use this check method while you are actually driving.
To address this in the past I have used a regular automotive “water temperature gauge” to measure the oil temp. I have done this in three ways (a) sender tapped into the end of an oilway. (b) sender tapped into the crankcase below oil level, and (c) sender just clamped onto the crankcase under a small block of wood. Basically, they all give good information and I think I would recommend the block-of-wood installation because it is simply less intrusive, and mostly you are interested in the overall engine temp just to know if it is more or less than usual.
Then I got a bit interested in head temp. there are gauges for this, specially for VWs, that cost heaps. But I found at Jaycar (a chain store a bit like Dick Smith used to be) that you can get a multimeter for $30 that comes complete with a thermocouple, and is also backlit. I bought one.
www.jaycar.co.nz CAT. NO. QM1526
this link might get you the item
All the best advice tells you that the wiring for a thermocouple has to be done with special wire and special fittings. This is because the actual temperature measurement is done by the voltage that is generated when two dissimilar metals are in contact, so any additional dissimilar metal contacts in the circuit are going to wreck the calibration. If you are going to use this device without extending the wires you will need to locate the meter behind the back seat (not an ideal location for making observations while driving, even using a mirror). So I did some experiments using boiling water and ice, and found that actually, the readings were hardly affected at all by simply cutting and extending the wires with ordinary automotive electrical wire.
I installed the thermocouple on the motor by crimping it onto a curved piece of postage stamp sized stainless steel and jamming this up between head fins as close as I could get to the combustion chamber of a convenient cylinder. You could do better than this I know.
The results? Normal slow running is about 85 degrees C and this goes up to about 135 deg C at 100kph. On extended uphill running it gets up to 185 and on the track (because of higher revs) it is about the same.
There is often quite a bit of talk going on about VW engines running too hot., and what to do about it. It seems to me there is usually one reason for running too hot, poor valves and poor compression. The fix is to spend NZ$350 on a mail-order set of new pistons/cylinders http://www.aircooled.net (they will send by parcel post and save you heaps, and this order is too small to atract GST. It's all win.) and while you wait (Ages. Months. This is the downside. Order in advance of pulling down the motor.) get new guides put into the heads and have the valves and seats done (doesn’t cost much, very simple work in the machine shop). This is not expensive and you get a motor that starts well and runs cool and is now 1641cc!.
Keep dubbing, do it cool. Brian
