Overheating, but only when going up long hills

[TheBigTater]

Hey guys, I have an 82 Sierra 4x4, 350/th350 and it has been in the low 90's the last week here and every time I drive up the South Hill it starts to overheat. I'm not loaded or towing and the hill isn't really that steep the grade just goes on for a couple miles. I can sit in traffic all day or drive around stop and go in the city and it stays at 195. The truck originally had a 305 and the PO replaced it with a GM crate 350. They reused the stock radiator, which doesn't look to be in the best shape but it is holding coolant and seems to be flowing fine. The thermostat is only about a year old along with the motor, and the water pump. Hoses are all newer too. Here's my thought- that radiator isn't enough for the larger motor when combined with having to cool the tranny fluid. If my thermostat failed closed it would be overheating while sitting in traffic. Any thoughts here guys? I'm on a shoestring budget right now since I'm an unemployed full time college student so I really want to avoid throwing unnecessary parts at it. Any help would be appreciated.

 

[f1shman]

Well, lets start out with the easy "free" things to check.

When the truck is cool, give the lower radiator hose a squeeze to see if the anti-collapse spring is inside of it. Sometimes they get tossed aside and not put back in.

Next give the timing a once over. Make sure your base timing is still set properly and not too far off.

Finally, you are either going to have to have an infrared thermometer or you'll run the risk of getting your fingers toasty. Let the truck run until it reaches normal operating temperature, then shut it off. Under the hood you need to either measure the temperature of or feel the tanks on either side of the radiator - not the fins in the middle core section. If there is a significant temperature difference between the two tanks your radiator has a restriction in it (or is the restriction) and should be either boiled out or replaced altogether with a larger unit.

Hope this helps you to diagnose your troubles. Try to let us know what you find out.

 

[89Suburban]

Well, lets start out with the easy "free" things to check.

When the truck is cool, give the lower radiator hose a squeeze to see if the anti-collapse spring is inside of it. Sometimes they get tossed aside and not put back in.

I keep seeing this collapsed hose spring thing. When I bought my lower hoase over the winter it didn;t come with a spring. Am I missing something? I figured they been phased out.

 

[bucket]

Most hoses don't come with the spring anymore

It's possible for a thermostat to cause your problem, if it doesn't fully open. I had a brand new one do that to me in an old 400 SBC. It could idle all day long, but as soon as you drove it, things got hot in a hurry.

You can also check between you radiator and condenser for a buildup of debris.

 

[towman]

check your fan clutch, but i would be willing to bet the radiator is clogged up

 

[johnmc]

your t stat could be stuck open and not letting the coolant cool down enough. or the radiator could be clogged. try to flush it .fan clutch slipping? does it still have a fan shroud?

 

[TheBigTater]

Ok I spent some time yesterday poking around and I'm pretty sure my Rad is toast. There are several spots where the fins have just rotted away and there is just bare tube left. Also found at least 4 pinholes in the core. I'm willing to bet that the inside looks just as bad. Fan clutch is fine (its centrifugal not thermostatic). Fan shroud is in place still. No AC condenser, all i have is a tranny cooler. I'm going to throw a new t-stat in just in case. It's a cheap part. Now gotta find a radiator for this thing without spending $300 grr. Thanks for all the help so far guys. I'll keep ya posted but it may be a week or two before I get around to working on it.

 

[towman]

i would think you can a rad for 150 or so

 

[bucket]

I bought an aluminum Champion radiator (the biggest one) on ebay, no complaints here. It was cheaper than the parts store equivalent too.

 

[TheBigTater]

Bucket, I was looking at those. I'd rather drop 2 bills and get an all aluminum rad off ebay. The cheap ones at the parts stores have plastic ends. I got the Mrs. sold on me getting an all alum 4 row off ebay.

 

[bucket]

If you replace a short rad with the taller version, you will need the correct upper panel... or you could just fab something up too.

 

[89Suburban]

!!!!!!!!!!!

 

[Jims86]

Wouldnt hurt to check your timing while your at it. Timing for the 350 is 4* BTDC

 

[dhamp]

i would think you can a rad for 150 or so

You would think......unfortunately not. And if I did, I'd be scared to try it at that price compared to the others.

 

[TheBigTater]

You would think......unfortunately not. And if I did, I'd be scared to try it at that price compared to the others.

I've looked at the autozone/oreilly cheapo $150 radiators and I just don't trust em. Flimsy thin aluminum cores and sketchy looking plastic headers, I just don't see that holding up under any kind of abuse. Jims86- Checked timing again and its good. I just put a new billet HEI in a few months ago.

Anybody have any thoughts on tranny coolers? I have an external tranny cooler that I can run. Should I still run an A/T radiator w built in cooler or would I have adequate tranny cooling from the cooler? If I can skip the built in cooler that'll save me a couple bucks. The external cooler i have is about 7''x12''.

Pics are coming. I'm still trying to scare up money to get her fixed lol.