Found this forum trying to research a potential problem.

'86 Ford F150 with rebuilt 300 I6 with about 5k miles on it now. Everything was replaced. New water pump, fan clutch, hoses, thermostat etc. Radiator was rodded.

To me it runs too hot. But I am not sure what the safe temperature range is. I finally put a mechanical temp gauge in this weekend.

I live in Arizona and it is summer. Winter comes around and I probably wont have any issues. Here is what is happening. First got the truck and noticed the the gauge runs right at the 'R' in normal. Never seen it there with the old motor. When hot outside and sitting at a light for a couple of minutes, the gauge would go to th 'A". I go into panic mode: turn off air etc and get moving again and the gauge goes back down. I immediately suspected the fan clutch. Mechanic says it is fine. So I put in a mechanical gauge to get some hard numbers. Runs between 190-200 during normal driving. Get on freeway goes to 210-212. Everything is fine. Get off freeway back to normal traffic, fluctuates between 210-215. Ok. Stop at light for 4 minutes, goes to 230-235. I don't know if it would go higher than that because I start to panic and get moving again somehow and it comes back down to 215.

Are these normal temperatures for the summer? 230 at a light? Seems to high. Nothing else seems out of the ordinary when that hot. No steam or pinging or things like that. The motor is a little noisier but that's it. I took it to the mechanic but I no longer trust him. He said he ran it for two hours with the air on and it never got above 214. I now know that's not true with the new gauge.

Is 230 too hot or not?

Wow, long first post. Thanks in advance for any wisdom you can share.

jason

 

1° Replace T-stat from actual 192°f opening point to 180°f.
2° My I6 towing 1.100 pounds, in city trafic with AC and external temp around 90°f never gets more than 215°f
3° Standard Fan cluch engages about 210°f or more it seems to me to high so I had replace the thermic spring in front by that one used on Carburators climatic control, then now it engages about 180°f
4° Iff temp gets 225 or more is very high, don't let it get more than 220.

Regards;

 

Had a similar experience after I rebuilt a 351W. Turns out that a freshly built engine has more internal friction which generates extra heat. I did not have the coolant passages cleaned which reduced the transfer of heat. Had the radiator "rodded", but it was not efficient enough. I eventually had a new radiator core installed and the problem was eliminated.

 

I'm happy if my 86 F-150 4x4 300 stays around the "orm" in normal, before I flushed the raditor an replaced the defective thermastat it used to be pushin L and sometimes blow water out the overflow.

Redneck-Cowboy

 

If you have a new t-stat, they can run high for a while. I put a 192 stat in my truck, and at new it would run at the r of normal. After a little time, maybe a month or so, it is down to running at the N of normal. Anything over 210 sounds a little high. Over 220 IS HIGH.

 

Sometimes I6 is litle hard to relase air inside water system, so thats the reason after any repair on cooling system it will run a bit hot for a couple of days.

Regards;

 

it probly shouldnt run much hotter than 190-200*. I would sugest putting a colder T-stat in the motor.

 

just a thought,is your fan on the fan clutch the right way? had one come in the shop the other day with a fresh motor that was running hot,found that the fan was on backwards.

 

Never had overheating problems, but the "dealer installed" AC didn't do much in city traffic. Last summer I replaced the stock belt driven fan with a Flex-a-Lite dual electric fan...big difference in two ways: First the AC works fine all the time, second it freed up a small but noticeable amount of power. The heater, another weak point, also works better in the winter since I can turn up the cut-in temp of the fans. In a full size van you need every bit of heat you can suck off that Pinto sized heater core.

 

Let's not forget that you're in the middle of the desert. A thermometer left in direct sunlight in my home town will hit 125-130 every single day in July. The air passing over my radiator doesn't want to accept much heat in the first place, plus it's less dense.
I flushed it out, put on a new radiator, T-stat, and fan clutch, and that took me from boiling over to R/M in Normal. Lucky for me the Canadian tourists all leave by May, so there's no traffic when it's hot.

I did just go look under the hood though and I had an idea. The fan isn't centered on the radiator, and it's a tad small to begin with. I bet that thing flows almost zero air through the left side of the radiator (thanks to the shroud.) Placing a larger electric fan centered on the radiator (with a new shroud), should help.

 

I live in carlsbad nm avg summer temps now avg around 110 to 115 have had my 83 here since it was new temp gauge at idle runs 220 all day drops to about 195 when i move, with or without the ac it does not change, even added a oil cooler( mines a stadard) didnt change anything, mechanics told 230 and below isnt a problem for this engine

 

Seems I may have had a radiator cap problem. I was checking things Saturday morning and pulled the cap off and it didn't feel right coming off. A little loose. It was the right one and showed no signs of cracking or other wear. It just felt weird, I don't know how else to explain. So I just replaced it. It's only $5. Well, It seems to have made a difference. 10 degrees or so. I've only had one long drive for the test but I am opptomistic.

Same 30 mile drive, 25 of it freeway. Warms up to 190 and after about 10 miles it has creeped to the 200-204 range depending on speed. Exit freeway at light moves to 205-207. Get moving again and it goes back to the 200-202 range. After two miles or so of the slow in town speeds it is around 198-200.

Looks good to me. Thanks for all the suggestions. We'll see how it shakes out.

jason