Hello folks. I am desperate for some help please. My 90 E250 4.6 has been overheating and I am "at my wits middle" trying to figure out why. I am not a novice, having put a new crank, head, etc. in this motor two years ago, but I need help with this. I have replaced the fan clutch, water pump, removed the thermostat, flushed the radiator, see no water in oil, couldn't see any oil in the anti-freeze. Did a compression test wet and dry,seems within reason, engine doesn,t seem to smoke at exhaust (as if bad head gasket). Knowing I would not be able to re-torque the head without pulling the intake , I sprung for the "Prema-Torque" head gasket when I put the enginge back together. It has run fine for 13K, but started overheating for no apparent reason, usually within 8-10 miles. I have noticed that a timing light shows a drfting mark at idle, the mark floats about 1/2 to 3/4 quaters of an inch. Could irregular timing be the culprit? Condemn the distributor? I even considered cutting out the catalytic converter, but I don't sense the clogged chugging or a sulfer odor. I need this truck to supplement my meager income and would really appreciate some help here. Thanks

 

try a new temp sender they can go bad. What temp thermostat did you put in? I live In ND and have bitterly cold winters so I use a 195F thermostat. my engine gets way hot after startup in the summer and then cools off once that thermostat opens. never had any probloms as a result.
Try washing the radiator. Just hose it down with a pressure washer. thatll blast all the dirt and dead bugs off allowing air to get at the fins. Vans usualy had small radiators to begin with.
I dout timing has aything to do with it but go ahead and tune up your ignition and reset timing if you want. It couldent hurt anything.

 

When you removed the thermostat, did you replace it with a new one? Don't run the engine without a thermostat. As for the cause of the overheating, the easiest thing to check is to first make sure the sending unit is giving you the correct reading as flipklos mentioned. Other possible causes include the block might need to be flushed, fan belt not tight enough, faulty radiator cap. The 300 is a relatively easy motor to keep cool, so the problem should be easy to solve.

The timing mark should not move under the light. Your 300 probably has timing gears so the only thing that would be causing that is excessive distributor shaft play, loose distributor hold-down bolt, loose damper pulley, or bad timing light ground. You mentioned you have swapped the crank out so is it possible you didn't tighten down the pulley bolt enough? If that's the case, it's possible your crank pulley isn't tight like it should be which could explain the shifting timing mark, and possibly even the overheating since the water pump is driven off the crank pulley via the fan belt.

 

I'm very familiar with the force pressure washers put out, and also familiar with how soft the fins are on the radiator (or condensor) and to me, IMO, the two don't mix at all.

 

I wouldnt use a pressure washer, but a plain wash with the garden hose wouldnt hurt.

 

Ive cleaned plenty of engines and radiators with a pressure washer and never had any major problom.

 

It sounds like a timing issue to me. Some times the springs in the advance mech of the distributor get worn and your advance dosent work. Id ceck on the advancing abilities of the dis