Hi,
I've got a 1989 Fi50 300-6 with EFI. I have had a problem with the engine running warm for awhile. Even though I live in Fla. it's still more than usual. I replaced the clutch fan (Bad) and the thermastate and hoped that would cure it,but still hot. I even switched to Mobil 1 syn.oil! No difference. Could the thermostate,even though new still be bad? This is a rebuilt engine and only has 27,000 miles. Any suggestions or help on this would be appreciated. I'm thinking of pulling the thermostate and trying to run it without one to just see what it does and maybe take a variable out of play??? Thanks!!!

 

Have you confirmed it's running hot with an aftermarket temp gauge, or are you using the factory one?

That factory gauge is unreliable in many cases. You might want to flush the cooling system and make sure your heater core isn't plugged up.

Also, and this is a big one...do you have the radiator fan shroud in place?

 

Never take the thermostat out, it will actually overheat if you do that. Get a meat thermometer and run the truck with the radiator open until it gets warm. When the stat opens, see what temp the coolant is.

 

Hi Gentlemen,
Thanks for the help! Yes I have the shroud on. No I do not have a aftermarket temp guage but can get something to use. I don't see how measureing the open radiator is going to tell me anything though? The heater core is possible. I guess I could pull the heater hoses and run a water hose and see if it comes all the way through and is not blocked! Thanks again!

 

Hi,
Ok- I pulled the heater hoses and put a garden hose to one end and water flows through the heater core freely. I don't see that as a problem but a good thing to check! Any more ideas? I took off the rad.cap and brought the engine to temp.noticed that the water dosen't move alot after the thermostate opens? Does that mean anything? Looking at the water pump now, is it moving water as it should? Is this a possible problem? As always any suggestions or help is appreciated!

 

did you test your stat before you installed it? if not i would pull it and test it, put it in a boiling pan of water, if it opens at least a 1/4in its good. if not get a new one.

 

Hi,
Yes actually I did test the themostat before I put it in but dosent mean it hasn't gone south in the mean time? Is it possible that the temp sender has gone wacky? Another thing is that the temperature guage will or can run at what I consider the "normal spot "and then an hour later going down the interstate at the same speed and conditions starts to run "hot"??? I don't know what changed in the system??? Thanks!

 

Does the lower radiator hose have a spring inside it? If not it could collapse restricting fluid movement when the stat opens.

 

This sounds more like a plugged up rad to me. Drain the coolant down far enough to see the top of the core in the radiator. If you have chunks of crap in it replace it.

 

Thanks Gentlemen!
These are things I can look at tomorrow. I do not know if my bottom hose has a spring? I will check that out. My radiator is new but I will check that also. I turned the engine off and then felt of the surface of the radiator and felt no cool spots everything felt even over the surface of the radiatior. I Assume it is a good radiator but will check it again! Thanks!

 

i would check the sending unit, possibly replace it as it is only 5 bucks at oreilly or napa. sometimes when they get put in people put teflon tape around the threads to seal it, if thats the case its not grounded right. just take it out and clean the threads and dap a small amount of rtv on it near the top of the threads. the sender is located on the drivers side of the intake manifold almost between your distributor and a/c compressor, sort of. youll see it, it only has one wire run to it.

 

Thanks Gentlemen,
I will check the spring in the hose and put in a new sending unit today. Another varaible out of the equation. Might be chasing a ghost? Thanks again!

 

Hi,
OK- I can feel a spring in the bottom rad. hose so thats not it. I looked for the temp sensor and all I see is a sensor on the thermastate heater hose tube where the heater hose connects,is this it? It has 2 wires going to this not 1. Anymore ideas are appreciated!

 

it is on the drivers side, almost straight in front of your injector rail. look in the front drivers side of your intake manifold, its the only sensor up there and it only has one wire to it. ill try to get a pic up for ya.

 

Ok I'm gonna throw this out there because it actually happened to me, dont know if this is your problem though.

I was rebuilding a 85 C10 Chevy pick up for a HOTROD. I converted the fan belt system from V Belts to Serpentine. Well at the time, I did not know that he water pump had to changed to a reverse rotation water pump. I had the over heating problems untill I found that out. I put in a radiator for a 454, the truck had a 350 in it. I even put electric fans and still the same over heating untill I found I need to change the water pump to a reverse rotation. After that, I removed the electric fans and put the 11 blade fan on with the new water pump and problem was solved, I miss that truck, I was fast, strong and break the tire loose shifting to 2nd gear and when you kicked the passing gear (Automatic tranny, I spent $1800 buck rebuilding that tranny)