I recently replaced my 1979 f159 351m thermostat and heater core as the heater core was leaking. I am concerned I purchased the wrong thermostat as the car seems to still be running very hot. I purged the system of air and really took my time replacing everything. What is the correct temperature thermostat ? Also could you guys point me in the right direction into fixing the temperature gauge in the dash it has been pegged to hot even when I first start the car. I'm fairly new to working on cars but since I live in Arizona I know I have to fix this or risk damaging my truck thanks for the help everyone

 

The 351m (and 400) takes a unique stat. It has a little collar that closes off the bypass when fully open for max cooling.

OE stat temperature was 192-195. I'd suggest you purchase the stat from NAPA... it will probably be a special order and take a couple of days. The OE stat will be fully open by 200-205 F so if it runs hotter than that it is not the T stat's fault. There is some other issue.

Now a question... if your gauge is pegged from start how do you know it is running hot? Is it boiling?

 

I just looked at the t stat I installed the guy handed me the Windsor thermostat.... I'll wait to install the correct one and i guess we will go from there.... The gauge has always been pegged since I have owned the truck it normally just sits out front and isn't driven so I'd like to take the steps to drive it as I didn't drive it in the 115degree weather we have had all summer as I didn't want to mess up the motor. Where would be a good place to pull up a diagram on finding the sending unit in the 351m ? Thanks for the help once again

 

The 351C/M/400 takes a special thermostat with a kind of collar around it. A 192-5°F thermostat is the one to use. Use only the Cooper-Robertshaw thermostat. This has been discussed many times in the 335 series engine forum.

Where to buy a 335 Series thermostat
3 options:
-Find a dealer with a RT-139 still in stock.
-Robert Shaw 333-180
-Napa*THM 297

Try calling a local Ford dealer and see if they have a RT-139.
Dealer in Kansas that might have one?
Bob Allen Ford 1(800)676-0675

 

The sender for temp is between the water pump and alternator. On the block.

Good idea to replace the sender... that may or may not fix the gauge. The gauge itself may be fubar. Also, they were not super accurate from new.

If the sender does not do it an aftermarket gauge using the factory sender location will tell you what is going on.

 

Here's the stock sender-in the front of the block, protected by the alternator bracket

I installed a real gauge with sender yesterday. Had to pull the fan, a/c idler, loosen the p/s pump, pull the pulley on the water pump, remove the two long bolts that hold the alternator bracket and swing the alternator out of the way

Then reverse the process to put it back together!

I'm in Arizona too, so I feel your pain...

 

To test the gauge, pull the plug on the sender and turn the ignition on. Gauge should stay at left or low end. With the ignition on and the wire grounded, gauge should go full right or high.

The sending unit is less than $10 but more than the connector that Autozone tried to sell me when I asked for the sending unit for a '74 F250 390 temp gauge.

 

DOAZ-8575-A .. 192 degree Thermostat (Motorcraft RT-139) / Obsolete

1970/74 351C / 1971/82 400 / 1975/82 351M

MAINER FORD in Okarche OK has 1 = 405-263-7242.

PHILLIPS FORD in Phillips WI has 2 = 715-339-3055.

ALBIA MOTOR CO. in Albia IA has 2 = 641-932-5416.

PRAIRIE MOTORS in Stanley ND has 2 = 701-628-2855.

MILLER OBSOLETE PARTS in Binghamton NY has 3 = 607-722-5371.

CARPENTER NOS OBSOLETE PARTS in Concord NC has 9 = 800-476-9653.
-----------------------------------------------------------------------------------
D7PZ-8575-A .. 180 degree Thermostat (Motorcraft RT-310) / Obsolete

Same applications as DOAZ-8575-A

MAINER FORD has 1.

GILLIAM MOTOR CO. in Dillwyn VA has 3 = 434-983-2026.

CARPENTER NOS OBSOLETE PARTS has 3.

 

Thanks for the updated info Bill.

ALBIA MOTOR CO have 0

Mainer 180's and Gilliam are 0 also, and have been for a while. I guess they do not update there inventory very often. You know how those parts guys are...lol JK.

 

I took these 3 Ford dealer sources from the Ford dealer parts locator which says that Albia & Mainer updated their inventory 9/6/2016 and Gilliam updated their inventory 9/4/2016.

 

Can't help what the computer says, I talked to a live human at both places and they are zero balance.

 

There's quite a few more DOAZ-8575-A's , I only listed a few of the sources.

 

Is this the correct thermostat they said its the rt139 I found it at a ford dealership in Texas

 

Mr Numberdummy, (Bill?) Where do you access the nationwide database on Ford parts like you always post for people here? Is it something that we could do on our own if we were looking for an old part? Or do you have special powers? -Thankyou sir.

 

Any answers ? Posted a picture of the rt 139 that the dealership said they had wanted to confirm it with you guys