The Stovebolt Site Forums The Shop Area General Truck Talk Radiator Cap Trick?

Members awhile back I barley remember some one saying to drill a small hole in the radiator cap....Can't remember why or how to do it..
I have just started my truck after doing some work on her. She seems to get to the H reading pretty fast. I have it idling in the shop. New fluids and thermostat, I believe a 180 degree.
My radiator is weeping fluid at the top 1/3 .
The radiator is from a 52 and it looks like it has had some repairs done to it already. I'm probally going to get a new one and start fresh...Any good ones out there that don't cost an arm and leg?
Anyway,since she has been dry for awhile I thougt that maybe doing that cap trick might help along with getting a new radiator?
Thanks

I think Joe means the hole in the flange of the thermostat, although putting a hole in the housing would let the air out - as well as the water
a hole in the rad cap would keep down the pressure but easier to leave the cap loose, just on the first 'click', which would help slow down any weeping from rad seams and pinholes

Bill

I often drill a small hole in the therm. itself to vent the air out. You can vent it by taking the heater hose loose at the connection just under the therm. As soon as coolant comes out sock it back on. That will vent out the air under the therm. If it still overheats after that you have another problem. A lot of new therm. are not good. If it heats up right away that may be the problem or the rad. could be plugged up.

OK Boys:
Do any of you have a pic of exactly where to drill on the flange/housing?
A good drawing will do also...I don't want to guess at this. I will also try the heater hose trick..is that done with or without motor running?
Thanks

I Put a new Radiator in My 50 from U.S.Radiator

install pic

Didnt cost an Arm and Leg...just the Arm


If the top 1/3 of your radiator is weeping as you describe it should be replaced.

Here is another pic of a drilled thermostat
...pic...

Good Luck

The motor should be running, so the coolant is circulating. Then it can force the air out.

Thanks guys, Dads, I checked out US radiators..they are about
$ 100 more than classic Chevy....Any reason I should pay the extra coin? Don't know squat about radiators and don't want to get burned...No pun intended.
Thanks Again for the pics, they help out ALOT.

This seems like an excellent tip. Wonder why they don't make them that way from the factory?

The OEM design didn't have a hole in them, as it really isn't necessary. I've seen OEM thermostat that did have them, usually on vehicles that have the thermostat in a position lower than the head, or it is is positioned vertically rather than horizontally.
I've personally never had a problem filling a system with an undrilled thermostat.

I purchased My U.S.Radiator about a year and a half ago. At that time there were several post on this forum about Cheap Overseas radiator being sold by the vendors. The overseas tanks were thin and some were not fitting well.

Decided to go with a U.S made radiator. I called Walker but they were out of my budget.

Several vendors now sell U.S. Radiators (Brand).Call around for best price. Check contry of origin.

Good Luck

Thanks Dad

You need to keep pressure in your cooling system especially if you are running anti-freeze. Heated anti-freeze at normal atmospheric pressure can produce glass crystals in your cooling system. That’s why you never run 100% and you always run it under pressure.

JimmiV, don't be bashful. Call the vendors and ask who made the radiator your interested in but don't tell them what make your looking for or it may be the one they say!!

I won't go into vendors here. As part of the homework call and ask at least two preferably three different places. Also not that there are a couple places that give Stovebolterts a 10% discount. (JimCarter and Classic Parts bot in Mo.) However, be ware that even with the 10% discount it may not be a good buy depending on "beginning price". Look at prices, discounts and shipping....see what the bottom line is.

Also think about if you will ever need a tranny cooler in the bottom and if so order it with the cooler in it now. Also ask if its a 3 row or 4 row...... and maybe the width of the cooling tubes. It may not make a difference in your application.....but then it might?

and lastly, there is a lot of good info here if you take the time to read it. It will explain a lot things.
http://www.usradiator.com/cores

I experienced air in the cooling system in the 355 SBC in my Model A Hot Rod a few years back.
Basically in the spring the first time I drove the car, after it was stored through the winter, it over heated. That simple little hole in the thermostat would have saved me a bunch of heartache and a bit of wrenching.

From my perspective the hole doesn’t hurt anything, but has the possibility of preventing a problem, so why not?

In 1972, I bought a 261 that came out of a 1960 school bus. The 261 thermostat housing and the water pump in that bus engine are different from the units used on a small-truck 235. The thermostat had a hole in it. I do not know if it was an original thermostat or a replacement thermostat, but it had a hole in it in 1972.

I don't have nay problems with drilling them, if you feel that it's warranted, it won't hurt anything. But personally, if the factory design didn't have it, it really isn't necessary. Proper filling and purging of the system should take care of any air in the system.
Tim, I'll have to look at the '60 manual to see if it was factory or not. I do know that the cooling system is different due to the bypass. I think '59 was also done like that on the 261.

Bill,

I do not know if the hole in the 1961 big truck thermostat is original (or, if the thermostat itself is original).

The 1961 manual shows a Dole-brand thermostat with bypass system for bigger trucks (with 261 or V-8s). The by-pass system is separate plumbing and a special housing (not used on the school bus that provided my engine). The two extra hose holes in the school bus water pump (for the by-pass system) were plugged.

It looks like Stewart/Robertshaw and other thermostat companies sold thermostats with 1/8" holes already drilled into them.

Speedway's prices on their generic is reasonable Jegs too.
Aluminum and twin cored. if you can find the right size.If you order a particular one to fit your truck, they are higher