Thread: Delayed overheating problem

Tweet

First off, thanks for the replies everyone! You guys are extremely helpful.

Originally Posted by 34_40

My first reaction is that you used a cheap poppet style thermostat.. if you did, replace it with a sleeve type. The sleeve type will flow more and maintain an even temperature.

I'd also try to get the fan into the shroud opening more. either add more spacer or add to the shroud??

Originally Posted by rspears

I'm tracking with Mike. My first thought was a sticking thermostat, hanging closed until the higher than desired temp can generate enough force to clear the interference. Also, like Mike says, the fan needs to be into the shroud at least 1/2 way, and ideally with only about 1/4" to 1/2" of blade on the outside of the shroud opening, and OD clearing the shroud opening not more than ~1/2", depth being just as important as "fit", IMO.

There are a lot of people that agree with your assumption that an electric fan is going to be more efficient than your mechanical, but I do not agree. With an aftermarket electric you will have more restriction at speed than a well fit shroud & fan, and while it doesn't seem logical the amount of electrical "work" required will load the engine just as much as the mechanical, and the mechanical fan will actually "coast" when the clutch disengages at temperature while the electric may still be energized. Your increased alternator load will require as much, or more power than your current fan. My advice is stick with the mechanical fan, replace the thermostat first, and then if that doesn't fix it look at the fan/shroud clearances.

Originally Posted by Mike P

Just a couple of thoughts.

The first is are you SURE it’s overheating. I have found some gauges, especially factory electric gauges on older vehicles to be very inaccurate. Factory tolerances, wiring and grounds that have degraded over the years and replacement sending units can all factor in to this.

A few years ago I spent a huge amount of hours and fair amount of $ changing fans and putting in a new radiator in a car only to find out the car was really only running at 190-200 degrees. Another one was my DD 84 El Camino that has a factory gauge cluster and the temp gauge in that reads a constant 30 degrees hotter than the actual temperature is. After changing the sender a couple of times and not being able to find a replacement gauge, I've just gotten used to it. I have found that a temperature gun is a great tool to have to start the diagnosis process before spending a dime on hardware (it's a lot cheaper than buying a new radiator you don't need).

The second thought I have is that what you are describing sounds like at speed the blades of the flex fan are flattening out and not drawing enough air thru the radiator at speed (as you slow down the blades curve more and start drawing the needed air). Just from my experience (other may vary), aftermarket flex fans often have blades that flatten out too quickly. Personally I prefer to use Ford 6 or 7 blade flex fans if I have to use a flex fan....... and for gods sake don't get hung up on the little oval marking that indicates who made the fan over keeping the engine cool.

Personally I prefer a mechanical 7 blade fan with a HD clutch (the thick one speced for BB Chevy trucks) over electric fans. The fan locks up at 210 degrees and with the factory 7 blade fan and shroud I doubt you have any more heating problems.

My problem with using electric fans is that generally speaking the cheap ones really don't pull sufficient air, and the better ones can put a pretty good strain on an older electrical system.

Anyway, that's my 2 cents.


.

Originally Posted by firebird77clone

Personal experience says: have the radiator serviced.

It's fairly common, the radiator is a little plugged up, and cooled the motor fine, but then you went and rebuilt the motor, and it now makes more power, and more HEAT.

Originally Posted by NTFDAY

If you're having cooling issues at highway speed you have more than a fan problem. As mentioned I would have the radiator re-cored and back flush the block and use a good quality thermostat along with the proper fan placed in the shroud. Also where is the timing set? If you're running mechanical advance are the counter weights free and not sticking? It's possible to drive a car at highway speeds with no fan, been there, done that.

Story time (replies to everyone below): I rebuilt it with my dad in Oklahoma, then had to drive my black car with black interior from Oklahoma to California (for college) in the middle of August. 30 minutes after driving it was overheating, and I had the heater on to try and help. I've never been in such a hot car my whole life. So I pulled off at a highway gas station (no town nearby) with the idea to remove the thermostat to increase the flow, but it didn't help. 30 minutes later (and driving ~45 mph on a 75 mph highway) I come to the nearest town.

Found a Pep Boys and went inside to try to figure something out. I had a lot of tools with me so I was considering all options. For a while I was going to install an electric fan. Pep Boys shop technicians came out to look at the car. One guy squeezed my radiator hose and tried to tell me that there was way too much pressure and I probably had a cracked head. He also told me I should leave it overnight so they could work on it in the morning (this was around 8 pm). Side note: he was an idiot/scammer right? The pressure in that hose is reliant on the pressure release valve in the radiator cap isn't it?

Anyways, I had less than an hour to figure something out before the shop closed and was starting to freak out a little. I bought another 2 inch spacer to get the fan further in the shroud but they didn't have long enough bolts. Spent nearly half an hour fiddling with the too short bolts thinking I could get enough bite with them. Then I asked what kind of mechanical fans they had, with the idea that mine was flexing too much. Then it dawned on me when they told me the sizes, I would just get a bigger diameter fan. I went from a 15" to a 17". The 17" barely fit, in fact it was so tight that it took a tiny bit of plastic off when I first started it up, but after a couple seconds it took off enough that it wasn't rubbing and was a perfect fit. Which worked very well at fixing the overheating problem. So I put the thermostat back in (fortunately the gasket was so new that it survived, Pep Boys was closed at this point) and continued the trip.

Spent the night at a friends house and set off at 3 in the morning because the temperature was still cool. Car was running well, I wasn't drenched in sweat, things were looking good. Then the sun starts to rise and it slowly gets hot again. Cooling by open windows just wasn't enough (it's ~102 degrees outside and again, black exterior/interior) so I am stoked about finally getting to use the a/c I paid a hose shop a crazy amount to replace the high pressure hose. I turn it on and hear squealing and immediately turn it off. So I pull off at a gas station and have my girlfriend turn on the a/c while I watch it and the belt is jumping on the pulling. So I assume my compressor had seized up after not being used for around ten years. Awesome.

So I then had to drive 2000 miles in this boiling hot car. We had towels with us, so at one point we laid them on our seat and the floor and started getting bags of ice at gas stations just to rub them on our skin, it was that hot. My left arm got sunburned so bad, it's actually pretty hilarious now that I can look back on it. Here's a picture of the car on the final stretch of the road trip from hell:





Despite the heat and car problems, it was actually pretty fun.