The Stovebolt Site Forums The Shop Area Engine Shop water not circulating

i have had my 235 running well for a few months now suddenly
the other day it ran hot and boiled the water out. even though the thermostat was a new 180 i replaced it with another new 180 deg.
refilled the rad got the air out cranked up still went to hot
and no flow to top of radiator. i removed the top hose and blew air
through the system. what do you all think the engine is a new rebuild and has been tanked. i cant think of anything that could be wrong with the water pump.

Might try it without a thermostat.

It is very rare but the impeller has been known to come loose. First take the heater hose loose right under the therm. & see if there is air in there. If coolant comes out try what Bruce says. About 1 out of 10 new therms. arn't any good.

Just a suggestion....crank it up and let the engine get up to normal operating temp.....shut it down and run your hand against the inside fins of the radiator.....the top should be uniformly hotter than the bottom. What you're looking for are cold spots that signal clogged passages.

Also check the bottom hose and make sure it has a wire expander in it. They've been known to suck closed, causing elevated temps and the dumping of coolant.

Dave

That's a good point about the lower hose. That is why most have a spring inside to prevent collapse.

Different application and Ive never had a water pump apart on a 235, but I had an s-10 and I chased that darn thing all over trying to figure out why it had the most erratic over heating issues, never the same thing twice.

After going through everything several times I pulled the water pump. The impeller had a small hairling crack in the center. So it would sometimes overheat and it would loosen up just enough to spin on the shaft and not circulate water. Sometimes it worked sometimes it didnt.

Just an idea.

Jeff

Phillip,

Excellent timing!!! Just went through this exact thing today. 216, fresh rebuild, drained the coolant to switch from a 160 to a 180 thermostat. Buttoned it up, filled it, started it. It was warming up fine, when BAM, it started puking water violently, out the overflow, AND from under the cap (non-original cap, by-the-way).

Problem was Vapor Lock.

My understanding is that air collects underneath the stat, and prevents the water from circulating. Not sure of the science behind it, BUT . . .

Tried an old mechanic's trick: removed the stat again, DRILLED a 1/8th inch hole in one side of the flange, away from the edge so it's within the circulation pattern. This allows air to escape to the top of the system (upper radiator) even though the thermostat is closed.

Yeah, I guess it defeats the purpose of the thermostat to a VERY small extent, but practically speaking, it doesn't make a difference in warming up. Just ensures the coolant can all circulate when it has to!!!

Won't hurt to give it a try, AND it's a CHEAP FIX!!!

-Michael

thanks for the tips im betting on either the vapor lock or the impeller. i will let you know what i find.

Wedge an aspirin in the thermostat when filling and it will dissolve after purging the air. A hole is good too.

Curt,

That is a COOL solution! Man, I'd feel like James Bond using THAT little tid-bit!

-Michael

OK, asked a buddy about the vaporlock. The scientific nugget I couldn't remember, was that:

The Thermostat only senses in liquid. It will never open if the bottom is surrounded by only air. I guess it takes the liquid contact to transfer the heat to the bulb, and make the stat open.

Let's hear it for science . . .

-Michael

actually Mike, in science, vapor lock is what happens in fuel systems when the liquid [fuel] turns to vapor, inhibiting the function of the fuel pump .... an air lock is what happens in the cooling system, when air [a "gas"] is trapped at the high point of a liquid filled system

Bill

All the new thermostats Ive seen already have a small hole slit to allow air to purge from the system.

the hole fixed the problem i will remember that one. philip

Great News!!! Glad to hear it.

Ironically, when I started up Rosie yesturday, the temp quickly headed to the red zone. IR thermometer showed the head was hot, but not the rad. or stat housing.

Pulled out the stat - my "vent" hole was plugged with what looked like lint!!! :mad: And this is AFTER we'd already had it up to operating temperature once before. Guess I shouldn't have washed my dirty socks in the radiator.

Anyway, put a second, slightly larger hole in opposite side of stat. Now, I just need to worry about how it will take slightly longer for the engine to reach a good temperature. AND, my radiator passages getting clogged by this silly foreign substance.

Oy, is nothing ever easy?!!!

-Michael

I just installed a new intake manifold and carburator in my 1960 apache. And suddenly, the truck overheats very quickly, a local man said it could be air lock, as the coolant was drained and replaced. He suggested I elevate the top of the radiator on jack stands and let it run without the cap on to purge the system of the bubble. Does this sound like good advice?

283 I assume, or V8 anyway - if you have an air lock it'll be right under the thermostat, no water contact on the sensor in it means no matter how high anything gets, the thermostat won't open to let the air out

pop it out and drill a small hole in the plate beside the opening, fix'er right up - helps to pre-charge the manifold so water is right up to the thermostat opening before you put it in too

Bill

I drill a small hole in all my t-stats. I also have another tool I use while warming up a fresh refill. It's a rather large funnel that attaches to where the radiator cap would normally, which elevates the highest point of coolant, which is often higher in the heater in new cars than the engine. I can watch it run and burp until I'm satisfied that all is good. Your local FLAPS should have one available from Lisle if you don't have the Snap-on truck coming to your door. I have both, one in my work box and one at home.

Devin

thank you very much for your response. the engine in the 1960 apache is a 1962 327 v-8, out of a corvette.

red, pulled out the new thermostat, no hole, put in the old thermostat which had a hole, works perfect, thaNKS AGAIN FOR YOUR ADVICE.