1998 Explorer kept climbing and climbing. Finally got home practically in the red and chugging and bubling. The next morining, I changed flushed the radiator and put new coolant in it. Took it for a test drive and right back up to the red. Now my question is regarding the thermostat.

If it was not working, as many people say that Ford Thermostats are not that good, wouldn't the upper radiator hose stay cool because no coolant was getting back to the radiator?

If it is the water pump, shouldn't there be coolant coming from the weep hole? Since the upper hose is hot and there is no coolant coming from the weep hole, what next? Thanks, in advance, Brendan

 

Yes, if the thermostat was stuck closed, the top hose should not get hot (in theory anyway). I'd still replace the thermostat before doing anything else to the system.

The other possibillity is that one of your coolant passages is blocked. I have no clue how you would go about finding such a blockage.

If the new thermostat doesn't help, I hate to say it but, your best bet would probably be to take it to a trusted mechanic or radiator shop.

Best wishes to you going forward.

 

Thanks Wayne. I figured it would be the thermostat or some expensive fix.

 

I don't suppose it would be the fan clutch? If you were in stop and go traffic and it runs hot but is cooler going 70 down the interstate it might be the fan. Also blow the fins out with air (not water) And check to see how cool the bottom hose is. If it is quite a bit cooler than the top hose the radiator is working good.

 

Ok, I replaced the thermostat (kind of fun) and it seems to be holding. However, there is a very small leake (and I mean small) around the front lip of the thermostat housing (where the three bolts go). I have tightened the bolts but don't want to tighten them any further as the are very tight. Any suggestions because I did not see a gasket or anything.

PS - Old thermostat had a lot of debris around and on it.

 

DON'T over tighten the bolts! Those aluminum manifolds can't take much torque. No gasket? or O-ring? Humm. I would take it apart and dry it out good and put a small bead of RTV silicone on the mating surface and reassemble it. Give it a few hours and put the coolant back in. That is the best advice I can give.

 

If your problem is your thermostat, that Explorer would overheat just idling. Does that happen or does it get hot driving in traffic. Or, does it get hot driving on the open road.

The thermostat controls the circulation. The water pump generates the circulation.
Blockages, except in extremely rare cases, usually only occur in the radiator and heater core. Also, the lower radiator hose can collapse while driving which restricts circulation. Feel it. If it feels at all soft or spongy, replace it.

So, for adequate cooling, you have to have airflow over a good radiator. A common failure is the fan clutch. If the Explorer overheats in traffic when your average speed is low this is the situation where the fan clutch would be suspect. On the open road, at highway speeds the fan and fan clutch are fairly irrelevant because of the airspeed.

So, assuming that you checked your fanbelt to make sure that the fan and water pump are turning properly, and the system is full of coolant, the next qusetion is, does it loose coolant?

If it looses coolant before it registers very hot, you may have a head gasket leak so then it registers hot because it looses coolant.

Or, does it get hot and then blow it's coolant out the overflow?

So, if it won't overheat *at idle* it's not the thermostat.
Then, you have to consider a partially blocked radiator.