My 89 has had some temp/coolant issues since I bought it. When I got it, the temp gauge didn't really work, it would register a little bit, but not really. I grounded the sending unit wire, and the gauge pegged out, so the gauge works. I wiggled the sending wire (which didn't look bad...) when doing so, and i got it to register a little better. As it is now, it will register between a little above cold and the N in normal most of the time. At times it will reach the N in normal, i've never see it make it to the middle of "normal".

I agonizingly changed the T-stat last night (kept leaking on me!!) and drove to work today....situation appears to still be the same...

It doesn't seem like the gauge is wrong, but I'm basing that on the fact that my heat works, but doesn't get super hot. My F-150 will get hot and i'll need to turn the heat down to LO, with the temperature setting in the middle.

On my 89, you've gotta run full blast for about 10 minutes of driving before it'll warm up the cab (this is a regular cab vs my F-150s supercab too), then you can put it on LO, but you've gotta keep the temperature setting all the way up. So it doesn't seem like I'm getting all the heat I should be.

When I got to work today, I put my hand on the upper radiator hose and it was warm.

Any ideas?

 

With a new t-stat, Id assume the engine is running at the right temp. From there, Id check the sending unit resistance values, and maybe have a look at the heater control valve to make sure its open fully. My 90 F150 usually rides around the o or r in "normal", and doesnt get super hot either.

 

Justin,
What temp t-stat did you install. We went to install one in Kris' 300 I6 and just happened to look a the flange and see 160° not 180°. Unfortunately Parts stores have problems also. My temp gauge runs exactly where yours is and I do have a 160° t-stat. I'd rather it run cooler than hotter.

 

My 92 In-line 6 has always been that way, and there have been a few different T-stats installed in the last 10 years. The only time it ever gets up in the middle of the temp gauge is when hauling something on a 95 degree day. The truck may have a stock radiator that works too well, no problem there, except the coldest mornings. The low gauge temp has bothered me for a long time and one of these days I'll install an aftermarket temp gauge on top of the dash.

 

This could be a big no-no. If you're engine doesn't reach proper operating temperature, the computer may stay in open loop and not enter closed loop. This will effect gas milage, emissions, and engine life in a negative way.

The T-stat I put in was a 192-195 (factory spec according to napa and autozone) degree version. I filled up the radiator all the way, drove aroudn to mix it up, and today I put a 500 degree thermometer in the top of the radiator, it never went above 170. I was gunning the throttle a little at the time, the thermometer went quickly to 150-155 then slowly made it to 170 after playing with the throttle. This in all took about 2-3 minutes. Unfortunately, it doesn't tell me if that is ok or not, because the reading is being taken from the radiator, and not at the intake area where the sender is.

 

Justin,
I run a 160° thermostat because I tow and am working the truck daily. Have had no issues with heat or cold, stat is set to open at 160°. On my actual (read aftermarket) gauge reading I am operating in a range from 174° to 195°. High was registered in the Georgia mountains pulling the 26' gooseneck with 4 horses, gear, water/feed to a weekend jackpot roping. Idle is at a standard 725 rpm and she exhibits none of the closed loop issues nor has she been getting any poorer gas mileage. In fact with the switch to all synthetic blend gear lube in the diffs and a change in the t-case as well as a recent tranny flush/filter change I am up from 10-11mpg aver age to 11-13 mpg. I am quite happy with that as gas prices this weekend are $1.72 for regular and $1.92 for 93 octane which I run due to the chip tuned for performance. No knocks. I just looked through your gallery, a very sweet truck, she is. Enjoy the rest of the weekend.

 

OK, well just wanted to point it out to you. I just hope you're 100% sure it's making it to closed loop. My mom's car was run for a long time like this with me unaware of it, at 92k it burns 2 qts of oil between changes.

 

Justin,
I really appreciate it. I know it's hard to believe but at 240,700 miles, I use no oil between changes (every 3,000 miles w/filter since new). I am very happy to be part of the board and everyone seems to contribute, some can be contrary at times, but that's human nature. The only thing I am finding a little unusual is that unloaded, with the tailgate down I had to run up to Banks County (65 miles one way) and when I checked the mileage I was @ 14.2 mpg. I just rarely experience anything over 13.5 mpg. It's not tank to tank transfer as I was just about empty when I returned in both tanks. Oh well, she's running well and I will keep up my end with th preventive maintenance. Here's looking to 300,000!

 

Sounds good to me then, I just hope i can fix my truck lol

 

Still leaking at the t-stat?

 

No, the leak is FINALLY fixed it appears (used silicone), the problem lies in that the temp gauge doesn't read normal, and the heat isn't the best so I thought maybe the engine was running cool. It doesn't appear to be running cool with the termometer test, but I tested the gauge like chiltons says, and it works fine, and the sender seemed to work (its a very simple device), but maybe that is bad and I should replace it...not really sure what my next step is.

 

My gauge never makes it to the N...I've only seen it ONCE that it made it there....an 18hour trip in the summer...lol.

You can check ECT voltage to actually see what temp. the computer sees.

 

Justin, there was a discussion, i believe, on this very forum not long ago about how the temperature guages register on this vintage of Ford pickups. It sounds like yours is among them. In #5 above you told how you put a thermometer in the top of the radiator, as you sort of suspected this doesn't work well in a crossflow(horizontal cores) radiator because the top radiator hose is on one side of the radiator and the cap is on the other side. The coolant cools considerably by the time it passes from one side to the other due to the fan pulling air through the radiator. Many times you can feel a great deal of difference by feeling one side of the radiator and then the other. Just thought I would point this out.

 

That is true, but if the side with the radiator cap is 160-170 degrees, that means the other side is hotter than that

 

Yes, that is what I was trying to point out. So your thermostat is likely working properly, despite what your in dash temperature guage shows.