I heard of an old trick years ago about getting rid of air in the coolant system. All you had to do was leave the rad cap loose (on about a 1/4 turn) and leave it that way for about 15 miles then tighten it back up. It does seem to work.

 

I'll give that a try...3 of my vehicles do it.

 

I had two reasons for getting air in the system. 1. The heater core finnaly got bad enought and started leaking coolant as well as sucking air on the cool down after shutdown. I replaced it. 2. Coolant jug hose did not have a clamp on it by the radiator neck. A cable tie was good enough for that. Now the radiator stays full, the babbling brook noises are gone but temp guage flutuates. I'll try cleaning the ground but will still install mechanical guages.

 

Just a side note to this .


The lower intake manifold gasket at the front and rear is susceptible to leakage of coolant on these trucks, which would also let air into the system. I 've had my truck for two years and it was by fluke I noticed this small leak.I looked everywhere and couldn't figure out where the little bit of coolant was going. This is NOT a huge leak it is deceiving (I beleive it only leaks while sitting)because it would only require the puke tank to be topped up once in a while which closely mimics normal evaporation. I have not got around to fixing this yet but I think it might cause the temp guage to fluctuate. I also think it has alot to do with my fluctuating idle problem.

 

I'm losing coolant but very very slowly. I have to refill the overflow tank about once every 1 1/2 months. Come to find out I have a frost plug that is leaking a little. Nothing I'm real worried about though...

 

I've got a similar issue going on. During initial warm up (about 5 minutes of city driving) the temp gauge goes up to the top end of the M in normal. It was going to the "A". But, I swapped the thermostat and got a little control back. Once the first cool down takes place (down to upper "O", lower "R"), it is pretty steady as long as I am moving. If I stop for a long stop light, the temp will creep up a little more than seems reasonable (upper end of R).

Looking at this behavior, I can see the thermostat opening and closing because the temp goes up and down in a more or less expected pattern. It's that first warm up and then idle temp increases that has me worried. It's acting like I am not getting enough air over the radiator (my guess). The thermo and water pump have to be working or I would not see the expected fluctuations in temp.

How does one clear air from the system? The fluid level looks good.

I had one other weird behavior on the temp. I was driving from the east coast to Colorado. The temp looked good all the way to mid Nebraska. (I will going around 85 or 90) and noticed the temp was running very high. I slowed down and turned on the heater to suck out as much heat as I could. I found that if I backed off to about 75-80 mph the temp was under control. I never did follow up on this. Also, I don't drive distances like that very often and I don't have occasion to wind up the speed like that either.

Just thought I would add to the general bucket of observations. Hope it helps and I hope I can get help.

-later

 

mkmchu, your issue doesn't seem to be the same as ours. It sounds like your radiator system is clogged up and not causing sufficient fluid flow. However, it sounds like you're suffering from a every minor case of this. My 72' RV on the other hand....was much worse.

Flush your radiator and coolant system out as best you can. Then see what happens.

 

Speaking of guages..I just took a good look at my choices on 351W '94 to install my new mechanical Temp guage sender pod. Looks like one choice is about 5" from the distribitor toward the A/C evaporator box. Putting Tee in there looks like no fun, may have to remove the throttle body. or........looking about 7" from the distribitor toward the firewall between the fuel rail and intake which looks like the overwhelming choice if it will work. I was thinking of a brass Tee and nipple there. I guess it's 3/8"NPT? Any advice would be appreciated.

I also have a new mechanical pressure guage. Plastics have been one of the amazing changes in my ol' life but I think I will go with stainless steel braided tubing rather than the enclosed nylon tube. I know SS is probably plastic inside but is protected from rubbing a hole. Does anyone know the fitting size on the tubing I need for the AutoMeter AutoGuage oil pressure guage? Is it -4AN or -3AN? I can't find any locals stocking the hose to try my guage on. Thanks again.

 

First, I've been told you can't use a tee when doing a water temp sender install. It will give an inaccurate reading. See my thread here...

https://www.ford-trucks.com/forums/s...d.php?t=365704

My suggestion is to remove the stock sending units for the water temp and oil pressure, and use the adapters (if necessary) in the kit to install their water temp and oil sending units, then route the wiring/tubing accordingly. That is what I did, however my edelbrock intake on my 393 has an extra spot for a sending unit, so I installed my stock water temp sender in the back of the intake to make it work again. The autometer gauges are on my A-pillar.

You can go the SS route, or you can put some small split flex tubing over the nylon or plastic tubing. I would do the latter, I feel the SS is not necessary. If you look at how the line runs from the sender, it goes straight accross to the crossmember/framerail and can be tucked next to the plastic fenderwell. Continue down the side of the framerail and over to a hole in the firewall. I have several holes in my firewall but all of them are in a line down from where the throttle cable goes through. It's a good spot, put a nice grommet and siliconed it up. The water temp sender wire can go down infront of the drivers side head, between the valve cover and the A/C compressor, and meet up with the oil sender's line...and the wires/tubing can go through the same flex tubing to the firewall.

Thats how I ran it on my 393, which I tried to keep everything as neat as possible.

 

Thanks! I can go ahead on this project immediately thanks to your suggestion. I sure want the temp to be acurate. The best engineering is simple and neat. I just had not thought of small split flex tubing and it is all over the vehicle. Duh!! . I think I will try a Tee and nipple on the oil pressure and try to install it from the top. i'm just curious to compare it with stock guage. Maybe it will not interfere with filter changing. I have the oil cooler so the filter is small.

 

Well, all the stock gauges are very inaccurate, at certain times.

The stock gauges are purposefully set that way. Otherwise, people would see the fluctuations that really happen, and if uneducated, would be lining up at the dealership for "I think there's something wrong with my gauge".

For example, my autometer oil pressure gauge will show the pressure at any time. When you change RPM of the motor, sometimes the oil pressure fluctuates. The stock gauge will not let you see those fluctuations, it's not reactive enough. It'll show you a gradual change, or delay if it's a sudden change (like a sudden loss of oil pressure would be seen on a stock gauge, but not necessarily in real time). Hope you follow me there.

I see no point in making the stock gauges functional other then appearance. I don't even look at my stock gauges on that side anymore.

 

"Today is the day we worried about yeaterday.......and all is well." I don't remember the author. I listened to you experts and now have mechanical Coolant Temperature and Oil Pressure guages. Yes!!! I have oil pressure. Yes!!! I have steady temperature. My stock oil pressure seldom got to the N on Normal and the temp fluctuated between o and r. My new mechanical guages read as follows. Start with 56psi oil pressure cold at idle. Warmed up with highway driving for about 20 miles then at 70mph got 51psi, at 50mph got 50psi. Stopped at light after that with A/C on got 31psi. @700rpm. Back home turned A/C off and put in Park got 40psi. @700rpm. Does this sound normal for 169K miles running 20W50 Castroil? AND, my old fluctuating temp was no issue. New mechanical guage slowly moves between 203 and 205 degrees.
All of you have great ideas and I thank you for your help.
I decided to go with AutoMeter AutoGuage dual mechanical set mounted under the ash tray and connected into ashtray light wire for "dimming." Used the supplied nylon tube for oil pressure but wrapped it with small split tubing like a wiring harness. Have oil cooler behind the filter and reaching the oil sender is no fun so I put a 1/4X4" brass nipple and coupling in the oil sender hole. Now the tubing connection can be reached from the fender. FINALLY found the temp sender (it is the one with one wire. You kept telling me where it was but I didn't look under the wiring connectors), installed the mechanical sender pod and ran it inside the split hose along with the pressure guage hose. Yes, not trying to hook up the old stock guages was a great idea. It makes all drivers hunt for the new guages and not subconsiouly glance at only the dash guages.

Now to select an oil. I had absolute no leaks until switching from 10w30 to 20w50 but that needs to go in another thread....... THANKS EVERYONE. All is well.

 

20W50 should cause LESS leaks for you not more. Something has begun to leak on your truck. Its not the nylon oil line is it

By the way I have an Autogauge Tach and bang for buck I think they're decent gauges.

 

Well i installed a new water pump thermostat and fushed added
antifreeze and it seems to be okay now. the only differance is the
gauge runs on the o in normal and not the n as originally. So
maybe the silicon in my clutch fan is weak, maybe the cuase for
the small differance.

 

How long has it been though? Mine took about 30 miles to act up.