The Stovebolt Site Forums The Shop Area Engine Shop 2 Questions

Hi All,
I'm new here. Please forgive me if I'm posting this wrong. I've just started working on fixing up a 1942 3/4 ton special Chevy Stakebed. I'll have many questions over the next few months I'm sure, but just two for now:
1) A mechanic who worked on my radiator put in a 180 degree thermostat, which seems hot to me. The truck isn't overheating anymore (many radiator issues were dealt with. Not just thermostat), but it's still running right at the red on the temp guage. I live in Colorado, so it's over 90 pretty much every day here, if that makes a difference. Should I put in a cooler thermostat?
2) I'm working on the rear brakes, one of which is leaking and the other has a broken parking brake cable. I tried opening them up and one drum came off very easily and the other didn't come off at all. I've heard that a worn braking surface can leave a lip on the drum that can't fit over the pads, but that doesn't seem to be the case. On the side that came off there was no visible wear at all on the drum (brakes were rebuilt 12 yrs, 2-3K miles ago). It seems to me that it's actually stuck on the flange that it fits over in the middle of the lugs. Any thoughts on how to get that off?
Thanks everyone.
-Jon

180 is a bit on the high side, as the 160 was probably more common back then. If it's not boiling over, the radiator is doing its job, but if the gauge reading has you worried, dropping back to a 160 won't hurt anything. If you plan on any winter driving, the heater won't work well with a 160 stat, though.

The brake drum is probably rusted to the hub, and should respond to a little penetrating oil and some moderate hammering between the lug studs to break the rust bond loose. Did the other drum slide off the studs, or did you have to remove the axles, and take the hub nuts off?
Jerry

180 does have me concerned, but maybe that's only because the radiator boiled over and sprayed antifreeze in my face (through the cranked out windshield) less than an hour after I'd bought the truck. Is there any reason not to switch between a 160 and a 180 with the weather?

I've tried lots of penetrating oil and some light hammering, to no effect. Maybe I just need to give it more of a whack? The other side came off with zero effort. All I had to do was take the wheel off and pull. I like things that are that easy

On the newer emission-controlled engines, lowering stat temperature is a big mistake, but an old stovebolt won't have a problem with it. Run a 160 in the summer to have a little extra buffer zone before it boils, and run a 180 in the winter to help out the heater. If one brake drum slips off, the other one should do the same. Some hubs have the lug bolts swaged over the drums, so the entire hub assembly has to come off. It's an 8-lug setup, right? That would involve unbolting the axle shaft from the center of the hub and removing it, then removing the 2-nut assembly on the axle tube and pulling the hub, drum, and all as a unit. If it just won't come loose, that's an option.

Try this stuff, it's the best penetrating oil I've ever used.

www.kanolabs.com

Of course, it's made right here at home, (Nashville) but I've used it all over the world with the US Air Force.
Jerry

For the brake drum removal did you back off the adjusters all the way before tying to remove the drum? Also make sure the emergency brake cable isn't actuated at all, ie unhook cable and make sure it moves freely.

something else you might check is the radiator cap if it is not doing its job of raising the boiling point you will boil over. get a higher rated pressure cap. ron

A '42 3/4-ton would use the same 6-lug rear drums as a half ton, as the 8-lug rear-end wasn't used until 1946. Does yours have 2 small screws holding the drum to the axle? Or a couple thin sheetmetal "speed nuts" that push over the studs and retain the drums? If no to these, then tapping and prying are in order after the shoes are backed off. Tap with a hammer mostly right around the center hole and the studs, not the outside of the drum. May require some heat applied around the center hole.

Jon,

In 1942, all trucks were equipped with a 140 degree thermostat; and, a 166 degree thermostat was recommended (for better heat transfer) if you used permanent anti-freeze. Most likely, the 180 degree thermostat is not the cause of your "problem".

The coolant is not supposed to reach boiling temperature in these trucks, so there is no need to get a high-pressure cap to allow the temperature to raise above the normal boiling point. I think a 0 psi radiator cap was standard on 216s and early 235s. By the mid-50s, Chevy trucks used 4 psi caps and cars used 7 psi caps (with the later 235s and 261s, a 160 degree thermostat was standard and a 180/190 degree thermostat was recommended/allowed on large-truck engines).

Before you start trying to further diagnose your "boiling over" (most likely it is not boiling over, it is a pressure "blow off"), be sure you are not overfilling your radiator. Since there were (normally) no overflow tanks on these old trucks, and the coolant expands as it heats up, it is normal for the coolant to overflow if the radiator is overfilled (Does your truck's radiator have an overflow tube? Is it clear?). The normal level of fluid in the Chevy-6 radiator is about 1"-2" below the cap. Have you let your truck warm-up and cool-down a few times to see if the "blow-off" stops at a certain level?

Tim

Jon,

I just re-read Barry Weeks' post about the brake drums (I did not know the 1/2 and 3/4 ton trucks had 6-lug drums until '46). Once you get the drums off, you might want to use a paper drum gasket when you put the drums back on (Chevs of the 40s has them for 6-lug 1/2 ton drums; or, you could make your own paper gaskets). These gaskets might help when removing the drums in the future.

Tim

Good point. It seems like whenever I pull rear drums off, the ones with the paper gasket still there come right off. And the gasket is usually still pretty good and the steel behind the gasket is shiny and clean. Without the gasket, everything is rusted together.

Pulling the drums can be a BIG job. One technique that works is to heat the drum - away from the axle. Firmly tap around the studs with a hammer in a regular pattern. You may also firmly tap the drum around its circumference. Be careful and do not apply too much force.

It is most likely that the "sticky" drum is corroded. You have to be very patient and keep heating and tapping, heating and tapping. Swearing helps, but only to relieve stress.

Good luck,

This works for me: After beating on the drum & cussing for 1/2 hour, I use a gear puller to put pressure on the drum. Then some hammering all around and it usually pops off. I hate rust.

i use 160 degree and 4psi in my 53 gmc 228 and it works great. keeps it almost constant 185 even in 100+ degree weather with the heater core circulation off.
tony