1957 GMC Overheating. Please Help!!!!!

Hey Guys,
I'm having a tough time figuring this one out. I've got a 1957 GMC stepside that is overheating. I gave it a good flush & replaced the fluids, replaced the thermostat & thermostat housing because it was filled with barnacle. It has an electric fan & I just put on a blade fan as well. Has the original radiator with no shroud. I know a shroud helps but & still don't think it should overheat as fast as it does. My next step is to replace the radiator. How do I know if my engine water passages are clean or blocked? Can I clean the passages while the motor is still in the car? I don't want to put on a brand new radiator then plug it up with crap that is possibly in the motor. Is there a test that can be done to see if I have a blown head gasket. I don't see any water in the oil. Please help. I want to drive my baby without stressing out about overheating.
Thanks.




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A head gasket can leak combustion gasses into the water jackets and not leak water into the engine oil.
And that condition can also cause overheating, as you might imagine. Not saying that is the case here, but among the possibilities.

Did this overheating condition happen suddenly or has been creeping up on you? Have you done any other work to the engine lately? Anything with the distributor and/or timing?

You may very well have a lot of sediment in the block, it's mazing how much crud can accumulate in there. But I wouldn't think that would be the sole basis of your problem. It requires removing the exhaust manifolds, removing the core plugs (aka 'freeze' plugs) and flushing and poking around the water passages with a stiff wire and screwdriver, etc.. The difficult part is getting the new core plugs into place securely with the engine in the chassis. Hmmm.....you didn't say if you have a 6 or V8. The 6 would be easier to do on the chassis. For that matter, you didn't say if you have an original engine or a swapped in engine. That, too, could have a bearing on cooling issues.

There are testers for combustion gasses in the water....check into that first. If that is negative, then I would suspect the radiator. Perhaps you can have it flow tested at a radiator shop before committing to replacing it.

I am not a big advocate of electric fans where an original mechanical fan can be fitted. Depending on the style and install, they can block more air than they provide. As for a shroud,....did your truck have one originally? If not, why would you need one now? The fan should be spaced about 3/4" to 1" from the radiator core surface.

 

Mine was overheating. When I removed the lower radiator hose, I noticed that the internal spring was rotted away. So the hose was sucking closed at rpm. Replaced the spring as she's cool as a cucumber again. Check your lower hose. Make sure it's not collapsing when the engine revs.

 

A cheap test for combustion gases in coolant: Take off the radiator cap, put a latex glove over the opening, it should be a tight fit. Start it up. If the glove inflates, you have your answer.

I would be more inclined to suspect your water pump since your t-stat was crapped up. I have run many of those type of trucks, no electric fan, no shroud and they always ran cool. Get the radiator checked and pop out an easy to get to freeze plug, that will tell you if the block has anything in it.

 

Check your radiator for blockage. Run it till it's hot and use your traditional radiator tester( your hand) and place it on the center of the radiator core. It should be hot....if it's cold/cool you have blockage. Radiators tend to clog up in the center first and the clogging works it's way to the edges. You can determine how much blockage you have by moving your tester from the center out towards the edges in all directions.

 

If it overheats when warming up, you may want to check the bypass hose/passages. If these are blocked, the engine will get very hot till the thermostat opens, then cool down.

 

Before I sprng for a new radiator I would have the old one rodded out.

Now as for checking things fire it up and get it up to operating temp, with the radiator cap off, is it circulating water? before it even gets up to temp does it look like a fire boat? if it looks like a fireboat then you have a blown head gasket as Hnstray suggests. if it is not circulating water or the circulation looks pretty poor it just may be that you need a new water pump, not a rebuilt water pump but A NEW ONE. Lots of times those old impellers get worn and don't really circulate water they just stir it up some, rebuilders seldom replace the impellers in a water pump.

here will be lots of other suggestions but here is a starting place for you.

 

Hah! that's a good one I'd never seen.

Normally I just take the cap off & stick my nose over the filler neck & smell the coolant. You can smell the combustion byproducts in the air inside the radiator if there's a cracked head gasket.

 

So I did the latex glove test & it inflated, but it took a while. Temp got up to 150 before it started inflating. It wasn't immediate. I would imagine that the glove would fill no matter what after an extended period of time. But maybe I'm wrong. Here's some pictures. What do you guys think. Should I try radiator, fan blade, & water pump before going down to the head gaskets. If it is the head gaskets is it as simple replacing the old gaskets & replacing with new ones or is it a major problem?
Thanks.




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Did you smell the gas in the glove? Did it smell like exhaust or blowby gas?

The air in the glove & radiator will expand from heat given enough time, & gaskets don't always leak immediately.

Any smog shop can wave a sniffer over the radiator neck and tell if there's combustion gas in the coolant.

I wouldn't tear off the head until you know for sure, and a special compression test can help here. It's called a cylinder leakdown test, and the instructions are widely published here.

If the gasket is bad it can eventually let a cylinder fill with coolant when the engine's sitting overnight, and you'll have a rude surprise when you try to start it & it hydrolocks.

 

The glove should fill right away, so I doubt you have a head gasket leak. Since this is an old truck, go with a new water pump or a good quality rebuild. From there it wouldn't hurt to have a radiator shop check the radiator out.

 

I also forgot to mention that it did get pretty got the other day & there were a couple of small homes in the radiator that were releasing pressure. The new cap never relieved though.




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BTW, are you sure the new thermostat is good?
I've seen a bad one right out of the box before.

 

The cap won't release pressure if the radiator has a hole in it, because the radiator will have no real pressure in it to release.

If this thing has holes, I'd send it to a real radiator shop to be boiled, roded, & resoldered.

 

did you feel the radiator with your hand or did I waste my time? If the radiator is clogged in the center you will see the water flowing when you look inside....but it will still overheat.

 

I have felt all parts of the radiator & it is hot everywhere when the motor starts warming up. Initially it stays cool in the area where the electric fan is but eventually that area gets hot too.




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Seems to be a good thermostat. Looks like right around 180 the truck try's to stay at that temp but eventually continues to creep up.




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ok....you eliminated the radiator being clogged. Do you see the water flowing when you look in the radiator neck?

 

I believe so. When I did the flush I would fill it up while it was running & water would pull down into radiator. I can really see if it's flowing though for sure.




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It has a curved neck so I'm unable to see down inside.




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If you do decide to replace the radiator go here first: http://www.championradiators.com/

 

Another thing I just noticed is that the motor is sitting a lot lower than the radiator. How can a shroud be used if the motor is that low. How can I raise the motor up? Will it still line up with the drive shaft?




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You are pissing in the wind. Leave everything as-is, forget the shroud and look at the radiator, water pump, hoses, fan belt first.

 

Ok. Got a new aluminum radiator on the way. Priced up a new water pump, & a new 5 blade 18" fan. Gonna put it all on this weekend & hope it resolves the problem. If it doesn't I'm going to throw a universal Fan shroud on. Wish me luck.




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I'm not sure why you asked for help as you seem to be of the school that says "throw enough parts at it and one of 'em is bound to fix it." Bob SS396 hit the nail on the head with his last observation.

 

1. coolant level correct.
2. cooling fan operational.
3. thermostat opening (watch gauge, check upper and lower hoses for temp)
4. check radiator core for temp
5. check radiator for flow (remove hoses and fill radiator with a garden hose, if it over flows before it pours out the lower, or over flows at a greater rate = plugged radiator)
6. check for combustion gasses in coolant
7. CHECK YOUR TIMING!!!

 

Ok. Well I've order a new radiator & will install it this weekend. Just for kicks though I'm going to check the old radiator with the hose flow test.
Not sure about the exhaust gases. I wouldn't even know where to begin with that.




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combustion gasses = block check device from napa, o'reilly etc.

 

Ok. Do I rent this or guy it.




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Sorry. Typo. Buy it or rent it? Thanks




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