Tackling the overheating headon (started work on Sat. 06/05)--Problem--Temp. went up to 120 with AC on in stop and crawl traffic and hovered at approx. 110-115 on highway.

1. To Toyota to get 2 bottles of fan clutch oil--$9.xx per bottle. Joked with the parts guy that I should drink it at that price. Bought the stuff anyway but ran out of time and will do fan clutch next weekend. Will report.

2. Locate and install 12" aux. fan in addition to stock elec. fan. Switches on from the pressure switch so that it is on whenever AC is on. Results are good so far. Temp. no longer goes above 100 even while in stop and crawl traffic on hot day. In fact, driving to work this morning without AC, the engine temp. was at 100. Then I put windows up and turned AC on for last 5 miles of trip on highway at approx. 60 mph. Big surprise, the temp. went down to about 97-98 and stayed down until I hit the street traffic/red lights and the temp went back up to 100.. I think the aux. fan must be blocking the air flow while off.

3. R&R thermostat, radiator hoses, and cap. Flush and refill. All done after aux. fan install and test--results did not change. On highway or crawling along, temp. hovers at 100 with AC on. That is probably OK for now, but in Aug. I think I will have problems again.

Strong suspicion that the radiator is not flowing well. Insides of radiator hoses were caked with deposits. Radiator probably clogged also. Will do fan clutch repair next weekend and report.

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1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead

When the cooling system is or was cruddy, make sure there are no deposits on the temp sensor that can throw off the gauge reading.

IMHO, 100C is high for a 617 with AC off. Something's not right.

Sixto
95 S420
87 300SDL

Agreed. I suspect the new thermostat. The temp was usually about 85-90 with AC off before I changed it out.

UPDATE from yesterday afternoon's 32 mile drive home in moderate heat--AC on all the way--on highway temp slightly below 100C. Then in about 8 miles of stop and go stuff, temp edged up close to the white 120C bar. Never into red and did not have to resort to turning AC off and heat on.

So, next weekend, I will take the new thermo out and test it and also do the fan clutch repair. Then, when those two steps don't work (I don't think they will) I'll check into the radiator situation.

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1984 300SD 326,997 miles and counting . . . No wait, my odometer is still dead