alright everyone. so as some of you know i have been dealing with an overheating problem. i have replaced the thermostat, radiator cap, and put a 16'' electric fan in there. the radiator is not rusty and doesnt look to beat up and when i plug up the radiator and fill her up with water then unplug the bottum of radiator it all seems to come out in a nice flow so im not thinking it needs a rod out. the previous owner said he put a new water pump in but should i trust that? it looks fairly new. keep in mind its 110-115 here in the az sun. i can drive about 6 miles before she decides to reach about 230 and i shut her off. she has a 160 degree therm. i cant seem to figure out what the deal is. im running about 50-50 with antifreeze. what are you guys thinking? any help would be greatly appreciated. oh yeah and its got a 302 from a 71 truck and has the origional v8 radiator(correct demensions for 1955 v8)

 

1st, I'd take out the thermostat and see what happens. I fought a heat problem that turned out to be a too restrictive stat.

Sam

 

How good is air flow? Fan shoud or if not how close is the fan to the radiator?

 

he says he drives for a while, so the fan and shroud won't be a factor (well, shroud only if its hold back the airflow)..

Sam

 

Maybe the water pump is the wrong one(reverse flow vs forward flow?). Maybe the impeller is broken?

 

does the radiator get hot? immediately when the truck starts
or later..

if u hold your hand on the top water hose, it should stay cold for a while, then heat up as the stat opens..

if the water pump is working

Sam

 

This is where I would look...if the pump is not turning the right direction it will cause all kinds of problems. With the engine running you should see water/coolant coming out the top hose into the radiator. With some radiators you can see this water flow without removing the top hose, others you will have to take the hose loose and remove the thermostat...

 

Let's not overthink this. Let's keep this basic until we can rule out a few things.

Is this a new problem? Has it ever run normally? What was happening before you tried to fix it?

How do you know it's 230 degrees? By what means are you determining this?

Why are you using an electric fan? What happened to the stock unit attaching to the water pump hub? How/where is it located?

Is the electric fan turning the correct direction? Many people have hooked up electric fans incorrectly whereby they try to push air back forward into the rad, causing overheating problems.

Why the 160 thermostat? (don't give me the 'because it was overheating' crap. The thermostat has nothing to do with keeping the engine cool, as you may have noticed.) 180-190 is correct for your engine.

The original '55 truck radiator should be more than sufficient for keeping a 302 at a normal operating temperature even on the hottest of days, if it's in good condition. Have you ever tried running the engine with the rad cap off? What happened when you did? (if you did)

This could be something as simple as an air pocket inside the engine from not filling it correctly. It could also be a stuck thermostat, or a blown head gasket. Overheating to that extent as quickly as it's doing it is not typically a water pump or air flow problem, unless the pump was actually broken or you had an extreme blockage in the rad somewhere. I've never seen a SBF water pump worn out to the point where it wouldn't move water. Your description indicates more an internal issue, like the ones I just mentioned here. Do some more diagnostics and let us know what you find. You shouldn't have to drive it to have it boil over. If you do have a problem, it'll do it right there in your driveway.

 

It's easy to put the thermostat in pointed the wrong way - it'll never read warm & it won't open to let the water circulate out. (A mistake I made much younger - Ask me how I know).

Ben in Austin

 

I have a stock fan [flexfan] and a 16'' electric . With this setup i can leave it running in the yard without running hot in 100 plus florida heat. But like wayne said maybe a bad head gasket.

 

It has not been a normal problem since I drove it home as stated. Po said it just needed a shroud but obviously it's not the case. Electric fan was just something I wanted to do. And if I remove the upper radiator house water come squirting out (thermostat out) and then I shut it off. How do I know it's 230? Well i I keep driving it gets to a boiling point so I know it's over heatin but my gauge reads 230. Thermostat opens correctly and I tried it without one and overheated faster. Electric fan is turning right way. There is 2 options fir the fan. Blow toward rad and blow from rad toward engine (which is the direction mine is going)

 

wayne has it nailed, with one exception. lower rad hose! this can, and will, collapse. is the wire wrap on or in this hose? is hose kinked just enough to suck flat? is bypass hose good? any chance this is a high volume pump? 160 therm is too cool for this engine. 180-185 is the sweet spot.

 

Fordman,

I am going to go out on a limb here the timing on the engine is correct right?

 

I have not checked the timing yet guys. I will go ahead and buy all new hoses today tosee what that does. Would a small leak in a hose cause this problem? But the hoses seem to be fine and don't kink on me. I'm starting to think it's a bad head gasket. Gonna do a block test to check that out

 

I'm also running a 71 302 in my 55; when I used an electric fan mine ran hot also, so I went back to a flex fan and used distilled water. Its gets up in the 100s here in SC and I don't have any more problems. My temperature is now 190 and goes lower on the interstate. I now this was mentioned before but a fan shroud will also make a difference, I used one from a Ford truck and trimmed it to fit.