The Stovebolt Site Forums The Shop Area Engine Shop Defeating Radiator Bypass - Truck runs hot!

Ok, big truck or 292 L6 owners - here is a question for you.

I have repowered my 59 1 ton with a 69 292 that came from a C50 dump truck. (as I was told by previous owner) Engine runs fine, but it is running hot in the Texas heat.

Now this engine has a bypass on it that runs from under the thermostat back into the water pump. We know that bypass hoses like this are used on marine engines, but this would make sense with a lot of cold water around. So without some heat retention from the engine via the bypass, thermostat would probably never open. Did big trucks also use a bypass like this for a big radiator?

Now that the engine is in my 1 ton, it runs hot, even with new everything (radiator, cap, and hoses). And the fan is only about 1/2 inch from radiator - no clutch - direct drive stock fan. And plenty of air goes through the radiator.

Engine almost overheats, almost. If the truck keeps moving it will not overheat. But with the big 4 core radiator I got for it, it shouldn't even run this hot.

Anyhoo, whaddyer know about these bypass thingys? And does yer 292 even have this setup? I am thinking about defeating it and then seeing how the thing runs heat-wise.

Have a look - I posted this on my web site so you could see the picture. This is a picture of my engine before cleaned up and installed in my truck. I used it because you can see the front of the engine clearly.

Click me to see the 292 L6 with funky bypass hose

Heavy duty engines have by pass hoses like that supposedly for more even heating during warmup.Don't kow if plugging it will make any difference, but try it. Since your truck has a new radiator and you seem to know what you're doing, all the small stuff must be ok.
Now how about the position of the fan,it it low and only covers the bottom part of the radiator since you say it heats up worse in town.And the engine is actually hot,what ever gauge is being used is accurate?And if so what do you consider hot? And the block is not full of rust and sludge?

I wouldn't remove the bypass, it is there to keep steam pockets from building up in the head and it keeps the water temperature more even to keep the cylinder wear even between front and back.

I don't know a whole lot about 292's, but I do know they are supposed to have a differant water pump than a 230/250, and the bypass thermostat plugs the bypass hole when it opens so all the water goes through the radiator.

I have only the one thermostat that I know about in the radiator return, is there supposed to be one on that bypass too?

Some thermostats have a valve built in that plugs off the bypass port when the stat opens. That passage looks awfully big to remain open all the time! Check the bottom of the stat housing to see if you need a blockoff-type thermostat. You could also run a pair of hoses from the bypass ports to a ball valve that could be closed, or partially restricted to regulate the amount of coolant that bypasses the radiator.
Jerry

Thanks Jerry,

I am actually going to do some 'old school' here. I have this washing machine that at my first house would overwhelm the drain because it emptied the tub so fast. I finally hose clamped a bolt to it to restrict the flow and then when I moved to a different house, removed the restrictor and everything worked fine in both places.

Going to try that here now, use a hose clamp and a piece of pipe.

Bet you $5 it solves the problem.

I don't get it,why would the bypass cause a problem on this engine and not the other 100,000 292's Chevy built?

I maintained fleets of 292,s for many years.
We never had heating problems. The later models
about 71 on up had a smaller bypass system.
Watch these thermostats they sell now. I have
had problems with them. Carquest has a premium
one. its stainless steel. Its worth the extra
2-3 $.

well...you all are right...and I am stoopid.

I blocked it off, it got hotter faster. But now I know (and everyone else too) that its not part of the equation. Inquiring minds ya know.... :p

I think the thermostat is ok, but I might get the carquest one. I put in this 'failsafe' one last time and it seemed to be a premium item.

I am going to make a custom shroud for it and see if that fixes things. I bought a stock one, but its for a fan that's farther away from the radiator than I can move mine, but I have a design in my head that should work ok.