I have just bought my son an '89 240 DL (1st car) and when we turn on the AC it tends to run hot but not boil over. Is this the Temp Compensator board or fan belts or water pump? We have changed the thermostat and fluids. And its starting to get real hot without the AC in the south.

db

 

I would look at the fan and make sure it is working properly.
Make sure the belts are adjusted properly.

 

I'm going to replace all the belts this weekend

db

 

Also make sure the fan is working properly.

 

Something else easy you can try is making sure there is adequate airflow through the ac condenser and radiator. They get dirty, and cannot pass enough air when the condenser starts transferring heat. Pop off the front grill, the two spring loaded plastic twist connectors, spray with a good cleaner ( 409 type cleaner, and/or the SeaFoam brand Bugs B Gone cleaner if heavy on the dead insects ) and then hose off.

 

Any tips on fan belt replacement, tension, etc. and what should I look for if fan is working properly? I can see no wobble, no broken blades, no noises . . .

db

 

Fan belt replacement is pretty straightforward.You might as well replace the ac and power steering belts while you are at it because they have to come off to replace the waterpump/alt belts. I find it easier to remove the intake snorkel to gain access to the two 13mm nuts that hold the pivot on the ac compressor. Loosen the 13mm nuts and back off the 10mm adjustment pawl and press in to loosen. Sometimes you can get lucky, and do not have to remove the ps belt. Loosen the 13mm pivot nuts on the alternator, then back off the 10mm adjustment pawl until you have room to swing the belts over the pulleys. Clean the pulleys if they are glazed or dirty, check the pump impeller and bearings by giving it a couple of good spins and shakes. When the new ones go back on, adjust the tension on the alt/water pump belts so there is about 3/8"+/- deflection, no need for a super tight belt with two belts on a pulley drive, and the bearings last longer. The ac belt needs to be tighter, about 1/4"- or less tension, and the ps belt about 1/4"+.