jnpcook

For a 1986 Ford F150 with 351

Which one of these is the one that is attached to the temperature gauge on the dashboard?

Oldrusty

Bottom picture is temp sender for your guage.

jnpcook

Thanks Oldrusty. I ended up replacing the item in the bottom photo and now my engine coolant temperature gauge is functioning again.

I also replaced a sticking thermostat with a new one. I didn't want to drive the truck as those two items are not a good combination (sticking thermostat and a non-working engine temperature gauge.)

Do you know how hot the gauge should read? I replaced with a 195F thermostat (the one that came out was a 192F but autozone only had 160F, 180F, and 195F for my vehicle so I went with 195F). My gauge reads in the normal range but on the high end just below Hot.

While replacing the thermostat and temperature switch I noticed the coolant is very dark and nasty. I will do a coolant flush and fill with new antifreeze and see where the temp gauge settles after I clean it all out.

Oldrusty

With a 195 deg. t-stat it should be about in the middle of the guage, you could use the 180 deg. to bring the temp down a little more. While you're doing the flush job,wash the outside of the radiator also. Spray water thru the cooling fins(from both sides) to improve air flow.

Since you will be pulling the boat,it would probably be a good idea to go ahead and replace the 195deg. with the 180 deg t-stat.

jnpcook

I did a complete flush tonight. The truck already had the prestone tee in the heater hose. I backflushed all the old coolant out through the radiator fill cap (coolant was dark black color). I then drained the radiator by removing the drain plug. I then refilled with antifreeze and then water. The manual said it was 16 quarts. I put in a gallon of antifreeze and nearly a gallon of water and the radiator was full. I had bought 2 gallons of antifreeze and was planning on adding 2 gallons of water to get 16 quarts.

Also I took it for a test drive. The upper radiator hose never gets firm. There is heat coming from the heater. Is it normal not to ever have the upper radiator hose firm? Do I have a bad water pump? I would think not if I am getting warm water to the heater core.

Any ideas?

Oldrusty

John, what temp did the guage show after the flush? I think about two gal. is normal volume in the system, I think I used a little over two gal. in
my 93 5.8,and I replaced my clogged up radiator with a larger one.

Did you burp the system after warmup,have you replaced the radiator cap?

If the water pump is not leaking it is probably still good.

jnpcook

After the flush the temp is still in the normal range but on the high end of the range. I forgot to spray down the outside of the radiator so I plan to do that tomorrow night. I found the problem with the limp water hose. It was the radiator cap. I replaced that today, idled it until warm, drove it a few miles up the highway and back home and felt the upper radiator hose and it was very firm now.

I bought a 180 F thermostat but haven't put it in yet. I hope to do that tomorrow night. I wish it was more accessible. Unfortunately the vacuum advance diaphragm is in the way of one of the thermostat housing bolts so I have to remove that (and make sure not to lose the tiny snap ring) in order to get the thermostat off, but I plan to do it anyway to get the temp down more in the center of the range.

Poo Bear

Ok. What is the name or part number for the bottom picture? This has become way to difficult to figure out lol. I tell the guy I need a temperature sending unit. He says I do not have that, I have a sensor. WTF? Any real names for these two?

Good old Bill

The engine could have both, the bottom PIC is the temp gauge sender, the top PIC is the temp sensor for the PCM.

Reo28

This is awesome!! i went to autozone yesterday to get a temperature sending unit and they gave me the one shown on the bottom. So i need the one on the top whats the part # for the top one? ill get the part # for the bottom one. is the top one located in the same place on the engine? thanks