Sorry if this is duplicate post but I did some searching and couldn't find what I was looking for and don't have a lot of time to keep searching.


I have an 89 Aerostar. I'll give you the specifics. Temp gauge used to read around the A in Normal on the gauge but now reads around the L. If it goes very much past that the Engine light comes on. I believe there are two TSU units, one for the instrument gauge and one for the ECM. I have checked the water pump, and it's looks brand new on the inside. The air flow through the radiator is good but I am not sure about water flow just yet.


Symptoms are that the van will run hot but not with the engine light on around town and at lower speeds. As soon as I run it up to highway speeds it will start running hot and the engine light will come on. If I slow down, it will cool off and engine light will go off.


From anyone's experience, what does this sound like? What are the chances that both sending units are going bad at the same time? Not likely I think. Does this sound like the radiator, which has been replaced but I don't remember how long ago exactly? What other tests does anyone suggest?


Thanks in advance for any help.


Doug B.

 

Check a couple of things:

With engine cool, open the radiator cap, start engine, and let it get up to temp. Carefully look into the radiator to see if coolant is coming out the tubes. If not, they're clogged. The upper tubes tend to get clogged first, from use of tap water leaving mineral deposits when the water evaporates.

When you removed the water pump to check it, did you happen to check the fan clutch? When it fails, it usually leaks the viscous oil that's part of the fluid coupling that turns the fan. It will leave a grimy mess inside the hub of the fan; you won't see t until you remove the clutch from the fan. If the fan isn't turning as it's supposed to, it can sometimes act as an obstruction.

 

Fan clutch doesn't appear to be leaking anything and is providing some pretty good resistance still. I put the old water pump (which is still pretty new) back in and replaced the sending unit for the gauge. We will see if that and having now flushed the whole system will do anything for this problem.

 

This tool will give you the engine temp in degrees so you can tell what the temp is when your gauge is on the A or the L.
Infrared Thermometer - Non-contact, Digital Thermometer

 

Yes, I have one. It works pretty well. I was getting readings of around 207 degrees at the sending unit. I was not sure if that was getting too hot or not.


However, the new sending unit, once I got the correct one installed, seems to have done the trick.


Two weeks of messing with this for a $9 part that would have taken 15 minutes to fix.


Thanks for all the help.

 

Long trip today with the van. 150 miles round trip, 5 hours driving around town and then the trip. Temp. gauge reading between the O and R in normal the whole time.


I would call this one resolved.