I have a friend who has a 78 F-150 Ranger with the 351M. He is having problems with engine temps. His main concern is how hot does the 351M run when sitting idle, cruising, and towing. He tows a old boat around. I have gone through the whole engine troubleshooting with him but nothing seems to be out of the norm. ie... thermostat, radiator cap, timing, water pump, block fushing, and the whole 9 yards. Any idea what the temps are would be a great help. He says it runs around normal no load 195 degree, then rises when towing which is normal of course. Thanks.

 

In the worst situations, if it never went above 230, I would say it is normal. Constantly going above 230 would be reason to investigate.

 

One thing I found out ( the Hard way) Make sure you have the correct Thermostat. The M Engine uses an internal coolant bypass, and the Correct Thermostst has a small "collar" around the sensor on the bottom of it that extends and closes the bypass when the thermostst opens. If you are getting strange overheating problems, this is a good place to start looking!

 

the 351m runs from 190 -200 with no engine load doesnt it? My 351m was recently rebuilt and it had a pair of numbered gauages installed, and after it warms up it sits at about 200.

 

My 78 351m runs between 'R' and 'M' of the stock NORMAL gauge settings. I replaced the thermostat with a 180 degree a few months ago and she never gets above the end of 'M', even in stop and go traffic during these hot summer days in Tulsa.

A quick and easy coolant check would be the coolant to water ratio. Most manuals say 50/50 mixes, but I use about 30 coolant and 70 water. Also, spraying the radiator fins out with the garden hose might help alleviate the heat problems.

 

i have a 78 with a 400 (same motor) and it runs about 200-210 and i have the HUGE radiator. i thought that was kinda hot myself. but then again im in Phx, AZ

 

I have a 78 F-250 with a 351M and Automatic transmission. Over the years I suffered with over heating in stop and go California traffic and when standing at idle during the summer for 20 years.

I recently rebuilt the engine after 200,000 rough miles (highway, back country and daily city) and found the right rear corner of the water jacket (around #4 cylinder) mostly pluged with a solid rusty buildup. After boil-out the block, I chipped out all of the rusty junk before the rebuild. Over the years I have tried every thermostat in the book from 0(none), 160, 180, 195 and 210. I have also tried several coolant percentages with no joy.

As part of my rebuild I installed a 4 row SuperCool radiator in place of the original 3 row. "Sha-zam", problem solved. With a stock 195 degree thermostat in place, the temperature gauge reads 1/3 scale all of the time after warmup. Even on the hottest days (100+ degrees). I no longer suffer from over heating or driveway puddles when I shut it off.

Flush it and give it some surface area and you will enjoy. Don't forget the correct T-stat. The stock temperature range is usually the best performer. Good cooling also keep an automatic transmission happy and lasting longer. A trans-cooler when doing a lot of towing can't do any thing but help.

PaPa Blue

 

You should always mix DISTILLED water with your antifreeze(50-50) to minimize the corrison that develops thru the passage of time--and the resultant clogging of the water jackets in the engine!!!fd