I'm wondering if anyone can help me solve my coolant temperature problem.

I have a 4.9L inline 6 1993 Ford F150. The engine temp gauge sits at or below the N on Normal and it is operating around 130 instead of 195.

I have put two different thermostats on it thinking they were stuck open. I'm concerned because it is getting very poor gas mileage and it will not pass our new state inspections.

I also replaced the catalytic converter, spark plugs and wires, distributor cap and rotor.

It is still sky high in CO and HC. It is running very rich and I think it is because the engine temp is so low but I don't know how to fix it because I can't find what's broken.

Please Help - I'm totally stumped.

Russell

 

Are you sure its engine temp related, you need to get a infared temp gun and check it at the t-stat housing to really see what the engine temp is, then go from there, maybe its another problem why its running rich. You can check the Fuel pressure reg to see if its leaking by taking off the vacuum line and run the engine to see if fuel is comming out of there, or smell it for gas. There could be numerous problems that can cause rich running. You could be having a lean misfire problem too, your HC and CO will go way up with a lean misfire. This could be your problem.

 

I didn't personally check the temp at the thermostat but I had a mechanic do it and he told me it was running at 120. I honestly didn't believe him because I just put in a thermostat but he thought the one I put in was stuck open so I agreed to let him put another one.

After that the gauge sits just where it has always sat.

There doesn't seem to be a problem at the Fuel Pressure Regulator, I checked what you suggested.

The car does not have any symptoms of a misfire. I would assume a lean misfire would show by hesitation or sputtering. Is that incorrect?

It runs great and does not trigger the check engine light but it is a fuel hog and fails the emissions.

I've looked at it and I have had two mechanics look at it and so far everyone is stumped!!

 

Well, a lean running engine, can cause those symptoms, a lean misfire will not show up like a regular dead cyl misfire. It wont be a total misfire. A lean running engine will not totally burn all the fuel air mixture hence the high CO and HC, this can cause allot of people to look for a rich running engine. Did your mechanic check the fuel pressure?? If not do that, check it to spec make sure its within spec. I can't totally remember those systems, does it have a Mass air flow meter, or is it a speed density type system. If it has a mass air, you can clean that, take it out and look at the wire, make sure there is nothing on it clean it with some intake cleaner or some alcahol on a Q-tip. Also check your PCV valve make sure its functional, and that it hasn't fallen out or anything. Have you ever doen O2 sensors??

 

I don't know about the high emissions, but I do know running 120 is just about impossible. I don't think I could get my 4.9 down to 120 in the summer even if I removed the thermostat, and put in a high speed water pump.
Try some trouble shooting yourself. Start out cold, and let it idle with the radiator cap off with the heater temp set to high, and fan off. Feel the different hoses. The heater hose should get warm first. The Top radiator hose should remain cool and the water in the radiator should remain cool. Fairly quickly the heater hose will get hot, but the top hose and water in radiator is still cool. If this is not happening, the thermostat is definitly not working. Let it come up to temp as well as it will, and check water temp with a thermometer in the radiator cap opening. should be just a few degrees below the thermostat temp rating. A cheap meat thermometer from WalMart would probably do the job.
I recently replaced all hoses, radiator, and temp sending unit on my 4.9. Had a 180 thermostat in from a previous owner. Replaced it with stock 190 and mileage went up about 2MPG.
If the test shows thermostat opening too soon, remove it and test it in a pan of water on stove. Use your thermomter and watch closely to see what temp it actually opens.
Might try testing the replacemnt before you instal it.
Again 120 sounds impossible.
Good luck Frank

 

Frank is right on. 120 is pretty much impossible. I had a thermostat stick open on my truck (300 six) and it sat at about 140. I would really skeptical of that mechanic.

I've had bad experience with the mechanical water temp gauges. The line either breaks right away or slowly leaks out over time. I would get an electrical water temp gauge - that's the only way you're going to know what the temp really is.

BTW - my stock temp gauge only hits the N when I have the air on. Other times, it's sitting about 3/4 of the way between the first white line and the N. I have a 195 t-stat in mine and it passes emissions with flying colors.

 

my 89 302 usually reads below N even though my truck runs way too hot. I can't even touch the water hose that's how hot it is.

 

I too have the same problem!!! I do not know the exact temperature but my needle stays below the N in normal. In the winter I have to put a piece of cardboard in front of my radiator or I get absolutely NO heat out of the heater. I have installed a 190 thermostat and it is the same. My truck will only get above the N if I am pulling my boat up a hill here (Idaho) in 95 degree weather. I have bought a couple of electric fans and am going to install them befor the winter. I can't take another cold winter with minimal heat out of the heater. Again, I do not know the exact temperature of the water but I do know it is not very hot....


Let me know if you solve this problem.

grumpy

forgot to mention that I have a 90 F150 with the 4.9 stock EFI engine

 

You could just have a clogged up heater core. You can't guess at the temp - you have to put a gauge of some kind on there. If it's not getting hot enough, the gauge will tell you. If it's running at 195 to 205, then you have some kind of problem with your heating system.

 

I'm going to verify the engine temperature here in a few minutes and I'll post what I found.

Thanks for the posts

Russell

 

Okay,

I just checked the engine temp and it is measuring 130.

I put a cheap temperature gauge into the open radiator and it never read above 130.

The upper radiator hose was cold and got warmer but it was never so hot that I couldn't leave my hand on it for a minute or two.

I'm sure the engine is operating above 130 but not by much.

It has a brand new thermostat in it so I can't imagine that this one is also failing. The heater, by the way works great, and the heater hoses are hot.
The a.c. on the other hand, is much warmer than it used to be. I'm not sure if the problems are related.

I really think the truck is failing emissions because the engine isn't heating up but I can't figure out why it's not. The car is not overheating so maybe it is stuck open, but how that could happen with a brand new one I do not know. This is the second thermostat I have played with in the last week.

Any IDEAS

Russell

 

I'm starting to think you put the thermostat in backwards. Did you follow the diagram and pay attention to which way you have to put it in?

 

If the thermostat was in backward it wouldnt open at all would it?

 

Hey Russel
I know you have to be getting a little frustrated. I don't think the thermostat is in backwards. Not positive, but pretty sure you would overheat if that happened. The thermostat I just replaced had one side stamped RAD. The other side had the pellet and spring assembly to sense the temp and open the thermostat.
I'm still thinking the thermostat is not working properly. Please pull it and look to see if it is completely closed. Then do the hot water test and see what temp it starts to open. I think it just about has to be opening way too soon, around 140, based on the 130 radiator temp you got.
Can you have two bad thermostats in a row? Yes, but only if you are really lucky.
Good luck Frank

 

Yeah, I guess it would have to overheat if it was backwards.

I'm just wondering why the heater hoses are hot, but the radiator hoses are only warm.