Have a 66 with a 289 and c4 trans she has begun over heating. I had the heads rebuilt put it all back together and ran great for about a month or two. Then started over heating. Only did it twice where the needle hit the h and I shut her down. Since I replaced the upper and lower radiator hoses the little 4" or so pump to manifold hose thermostat water pump and pulled the heads and replaced the head gaskets just to be sure. Got her put back together and bam still doing it. Like I said I don't know where to go from here. Thanks

 

is it over heating cruising at highway speed or low speed. how is it just sitting. you running a shroud? is the fan clutch tight or you switch to electric ? is the stat sticking? is it the stock radiator?

 

No shroud was actually gonna pick one up today. Stock fan on it

 

shroud makes a huge difference but when is it getting hot while at cruising speed or driving slow/at idle?

this may takes some steps to get to teh answer.

 

And haven't road tested since putting back together just idle test

 

Heading to part store now to pick up performance 6 blade fan and wetter water. Then my mustang dealer tonight for shroud bracket kit

 

This will most likely fix all your issues.
P.s Autozone is buy one get one free on wetter water for this month

 

IMHO water wetter is snake oil. a good 50/50 mix is all that is needed and if teh system is in good shape then it should be cooling.

example my car is 21y/o has the stock rad, stock fan and police fan clutch. i have a new water pump and a mild H/C/I. The temps in my area have been running in the high 90s with very high humidity and I had it out the past sunday and yesterday. The car ran at perfect 210* w/o any problems and I only run a 50/50 mix.

keep in mind the shroud helps to direct the air flow across the surface area of the radiator.

what we need to find out is if it is because of the lack of a shroud, if you have clogged tubes in the radiator which is reducing its cooling abilities, if you have air pockets or if the head gaskets is shifting slightly on you during assembly for starters.

The car should cool fine with the stock fan, stock radiator and proper coolant mix. Highly modified motors do need more cooling but it sounds like your are pretty much stock or mild. don't waste to much money yet.

 

don't totally agree...now lets go at it .

I have tried royal purples stuff in the past and it didn't do squat.

oh and nice to see you around again, you have been quiet lately or maybe I'm missing your posts.

 

unless you have a super efficient system it WILL run hotter sitting at idle ...

 

Ladies ladies you are both helpful the more opinions the better. Gasket didn't seem to shift sitting install as it has the bolt pegs that keep it in place as well as the notches lining up for the intake manifold gasket. I am hoping the shroud makes the difference. Hopefully my guy has one he has to check his shelves and get back to me. If the above doesn't work I am guessing the next step is a replacement radiator right?

 

next step is not repaling the radiator. you have only had it at idle so you need to road test it again once the shroud is on. then I would go from there, the radiator can be tested and cleaned but you could also have an air bubble trapped from the coolant being drained out.

 

Also the drain bolts on the block are stuck. In case there is air behind the thermostat would popping a 1/4 hole in the thermostat plate help get the air out? Also I did see the water cycling in the radiator as well

 

Moving water is a good sign - the thermostat is open, but I can't see it holding air if that is the case - that usually works itself out fast on the old blocks.

Is it even possible the overheating is a different or phantom issue? Is that gauge new/accurate? What temp is the thermostat? Could they're be some other factor generating more heat than necessary: timing, bearings, exhaust...

You could also do the ol' boiling water & cooking thermostat to make sure it's cracking open at the advertised temp - I replaced a broke OEM 180 thermostat and was given a 195 (by a "that's what the OEM book says" sales tech) which was just wrong - it went all the way to just under "H" which was obviously bunk - When I had older stuff, I always went 10 degrees cooler anywho.

 

The gauge is original but sending unit is new. I am fairly certain the gauge is working because when it originally over heated the oil pressure started going down a little

 

Also timing was just set within a minute of initial firing after gasket swap. Exhaust is dual and appears to be flowing fine

 

I would look at using an aftermarket temp gauge. your local parts store probally has one cheap and you don't have to install it premanent just temporary to get a good real temp reading. also you can see coolant flowing but it can be from the 1st few rows and maybe even the a few bottom rows and coolant is moving but all it takes is a few rows to be plugged to get a problem. I good temp reading under driving conditions will really help number not letters is what we are after.

 

Also wouldn't bad bearings make some noise? Alright picked up new flex 6 blade fan. If anyone is in Washington I highly recommend ricks pony parts. Talked with him and he says he may be out of stock on the should but it told him I needed it to try to be in the round up on Saturday. And he said measure my radiator and he will sell me the new one off of his. That my friends awesome customer service. Getting the shroud at 6 pm my time. I will have it all on tonight and will update u thanks everyone.

 

Not so much the water wetter. I'm saying the shroud will fix it...
And I've been busy

 

Doesn't matter I was really joking. busy is good & bad, glad you are well though.