[casioqv]

I leave in 2 days (sunday morning). My planned car modifications are done so I'm focusing on putting brand new brakes and wheel bearings on the trailer.

Originally Posted by v8volvo

These may be too late to count now, but a few suggestions in case

Great advice, this is a lot of good stuff for me to consider, and it did come in time. I always appreciate your advice, I recently purchased a 2001 golf TDI for my wife, and reading everything you wrote in the past about the 01m was very helpful.

Originally Posted by v8volvo

Low gear, elevated engine speed, light load

The relationship between EGTs and engine temps isn't something I thought about a lot before, but I can see how that will be critical. I will definitely use the high rpm/low throttle technique. In the past I have always used full throttle up grades.

Originally Posted by v8volvo

80C Wahler t-stat, part # 035 121 113

Why is the 80C better than the 87C? Won't they both be full open all the time up a grade? I currently have a brand new 80C BEHR, and a brand new 87C Wahler but was planning to go with the 87C Wahler. Should I put the 80C BEHR in instead?

I haven't collected a lot of data, but it seems my fuel economy has been much better in the past with an 87C vs 80C thermostat.

Originally Posted by v8volvo

you're only measuring at one (stock) or at most a few points -- temp could be higher elsewhere

That is a good point. I do have a very accurate digital temp gauge mounted to the head itself, and I've found with my infared thermometer that this usually represents the highest temp I can find on the exterior of the motor. However, I suppose I shouldn't expect the hottest part of the motor to be the exterior surface!

Originally Posted by v8volvo

I usually operate with the assumption that anything outside the range of normal operating temp (i.e. exact middle on the gauge -- let's say up to 100C) is not safe for the motor

I agree with you, but in that case the D24T may not be suitable for towing at all. On other motors (such as Volvo red blocks) a good condition cooling system will never let the motor exceed 100C.

My experience with D24Ts is that they can't even get the fan clutch to engage solid until about 110C, and aren't seriously throwing off heat until close to 120C. Hopefully that will change now with my giant oil cooler, and 100% dialed in cooling system. I've done some full throttle runs up long grades without a trailer but with the A/C on in over 100F heat, and I currently can get it just to 100C but no hotter.

Before my cooling system improvements I have ran this motor to 118C without problems, but I may have been pushing my luck.

Per your advice, I will (instead of pushing the limits) go as slow as I possibly can, and stop as often as possible to let it cool. I will be going on a Sunday morning before sunrise, so I should have virtually zero traffic. Climbing at very low speeds in the rightmost lane is considered acceptable anyway on the grapevine.

I have blown head gaskets twice in the past on D24s, but both times there was a total loss of coolant, rather than simply getting warm with the coolant remaining liquid... and both motors had fiber gaskets. My current motor has an MLS gasket, and also has a giant 1.5 gallon coolant reservoir with a float sensor in the very top of the range.