The Stovebolt Site Forums The Shop Area Engine Shop 1957 GMC Overheating. Please Help!!!!!

Hey Guys,
I'm having a tough time figuring this or 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 should. 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.

what engine, not stock? a shroud helps if the engine fan is set back from the rad too far, which will be the case with a non-stock V8 in an original 6 cylinder truck, if the fan is more than 1/2-3/4" away from the rad, get a shroud .... and ditch the electric fan

Bill

How's your water pump? Does the water move through the system? It seems that if your thermostat had crusty rust on it, that your water pump might too.

looking at mr Watts other posts, he got the truck with a 350 already swapped in - no doubt the whole problem is the fan is way too far from the rad, in 57 a V8 truck had the rad moved further back, and an electric pusher isn't likely to suffice

Bill

So I did a latex glove test that I heard about to check for a blown head gasket & the glove inflated which is supposed to indicate a blown head gasket, 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.

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.

Get yourself a shroud,and when you fill the radiator,run the engine with the cap off,and keep squeezing the upper radiator hose. This will help burp the system of trapped air pockets that cause overheating problems. i did the same thing to my 261,and it kept overheating until a mechanic friend burped the system for me,(running a garden hose through the cap,constant cold water,so it wouldn't overheat). Keep the petcock closed,and let it overflow out of the filler. also set it a t high idle,between 1,500-2,000 r.p.m.'s,to let the pump do its job. He burped mine for about 10 minutes,and I immediately drove it home,and drained the water and added coolant. I burped the system,as he did,and the engine didn't get hot enough to burn my hands,after running for 10 minutes at high idle. Truck hasn't overheated since. Hope this helps.

you didn't link the pictures .... forget 'replacing' things until you do a proper diagnosis of the problem, if there is one .... that 'latex glove' thing is over the fill neck with the cap off? all that tells you is water expands as it heats up and increases the pressure, that's why you have a pressure cap on the rad but if you're getting pressure release via rad seams, your rad is failing, possibly from too high a pressure cap, it must be a max of 7psi

you haven't indicated if this is as I said, a V8 in a truck that was originally an I6 so there's 5 or 6 inches between the engine fan and the rad, in which case your 1st step needs to be getting a shroud, might end the "problem", except for the damaged old rad there may not be anything wrong

also, if it's not pushing water out the overflow, what indicates it's "overheating"? have you checked it with a laser thermometer? are you depending on a gauge [original or add-on]? a 350 can easily run 200-210* without problem

Bill

As Bill was saying, about the fan being too far from the radiator. Back in the old days when we swapped a small block V-8. A spacer with long bolts was available almost anywhere to move the fan out. They were made out of alminum. I think you could get different lengths in order to get the fan about 1/2 inch from the radiator.

Derale makes them, and they are available at any speed shop (Jegs, Summit).

http://derale.com/products/belt-driven-fans/fan-spacers

Their note: •Warning: Fan should have a minimum clearance of 3/4" from the radiator, belts, hoses or pulleys

this shows the factory setback of the 5-7 rad for the V8, don't think a spacer does the job, the common plastic shroud is what works, or the original style used in 58/9

Bill

Yep, and I notice there is a spacer there too. Actually I remember them coming from the factory with spacers on lots of cars and trucks.

Ok guys. Here's the Update. After 2 late nights this weekend. I finally got everything pulled out & put back together. It ended up being a bigger job than I thought it would be since the motor & truck aren't original to each other. Anyways to make a long story short. After pulling everything off the motor I jammed high pressure nozzle against the water pump holes & flowed it until clean water came out both ways, I replaced the water pump, radiator, upper & lower radiator hoses, new coolant, & few other little things. Fired her up & got her to temp. Put it in drive & held my foot on the brake for 10 min to simulate sitting in traffic & then today I drove it for 15 min on the freeway & she never got over 185 the entire time. Also just to add some icing to the cake I dropped the drive shaft & replaced the rear transmission seal (was leaking), replaced the rear u joint, & changed the oil. I think the issue was the radiator. After I pulled it I realized how jacked up it was. Anyways, Now I get to enjoy her. Thanks for all the helps gents.

I can't figure out how to link a picture.

gig, you need to have the pic hosted someplace like photobucket, etc, then just go to that pic and copy the address and come back and paste the address in the text box, it'll show up as a link

Bill