Hi everyone, it has been awhile since I've posted here. I have a 1983 244 Turbo that has a problem that I'm having some difficulty solving.

The car has 321,000 miles. I have rebuilt the engine, replaced the steering components, all suspension components, brake components, etc.

two weeks ago everything was fine. car ran very well. Then the temperature gauge (coolant) started going high. about 3/4 of the way up and stayed there. It slowly rises while the car idles.

Here is what I did.
1. replaced thermostat (first thing done). no change
2. replaced temperature sending unit (for gauge). no change
3. Replaced fan and fan clutch. no change. This is getting old.
4. Replaced water pump. No change.
5. removed intake manifold (again) and checked the wiring from the temperature sending unit to the gauge. continuity is there.
6. Grounded the yellow wire from the sending unit and the gauge went all the way up.
7. Replaced temperature sending unit for ECM. no change. (didn't expect a change there).
8. Removed radiator and flushed it excessively. Some rust and bits. Added CLR Just in case. let it sit awhile and flushed again.
9. Removed hoses from heater core and flushed excessively. Some rusty water but after awhile it came out clean.
10. REmoved hose from engine to heater core, forced pressured water through hose through heater core and back out engine. no change.
11. Flushed engine. (drained from petcock in rear and flushed.) clean water
12. Rechecked engine timing. Spot on at 12 degrees BTC.
13. Rechecked RPM at idle. Spot on.

Engine idles all day and doesn't overheat, but gauge goes to 3/4. Hmmmmm
14. Checked temperature on hoses. Bottom hose at 58 degrees C, Top hose at 68-71 degrees C. I used a infrared temp gun. I have to admit, the top hose is very hot to touch. I wondered many times was the brand new thermostat not opening? I replaced it with another spare I had and no change I also placed all of them in water, brought it to boil and kept tabs on the temperature and they all opened at 88 degrees C like they were suppose to. Hmmmmm?
15. Checked for air in system. let it run with no cap and got all air out.
16. Removed instrument cluster and checked board. Okay.
17. Replaced gauge regulator transistor (had one handy so why not?) no change.

I ordered a new radiator, it should arrive next week from IPD. However, I'm now at a loss. what am I missing? Could I have mistimed it? It did take quite awhile to get the timing right. I had made the mistake of removing the distributor and that didn't help at all. Got all timing marks spot on (several times). Had to remove and reinstall the distributor according to the manual many times. But I got it (I believe). It fired right up. The other times it did not. You could tell the timing was way off. Adjusted it to 12 degrees BTC and it runs great. But the temperature gauge????

Any thoughts? I'll let you know what happens when I get the new radiator. But this sucks.

Thanks,

1983 Volvo 244 Turbo 321,000 miles
1995 Volvo 850 T5R (fully restored) 298,000 miles
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