I need your help Bricksters. I am still trying to track down the problem of an overheating B21 engine in a 1976 245 project car. I took the radiator out and had it cleaned internally by a shop. New thermostat. New temperature sensor. Bentley's troubleshooting of the guage checks out ok: when wire grounded, guage pegs hot, connected to a 68 ohm resistor it reads about 3/4 or slightly higher.

With the thermostat out, the car runs pretty cool, barely into the green. With the thermostat in, guage runs right up to and just into the red. This is a new thermostat(88 deg. C), and it opens fine when heated on the stovetop.

The previous owner had neglected the cooling system, running the engine without a thermostat or changing the coolant which was horrible looking. Looked like rustly water possible greyish, not green at all.

So what's left to do? I am assuming the water pump is circulating water because with the thermostat out the engine stays cool. Am I looking at a blown head gasket? I get some steam out the tailpipe with thermostat in and engine running hot, but running cool with no thermostat no steam present. Idle quality is ok, considering condition of motor mounts.

How can I tell if combustion gas is getting into the coolant and would this overheat the engine quickly?

Thanks in advance,

HighMiles

Found the problem! Turned out to be the voltage regulator behind the temp and fuel guage. After trying 2 wrecking yard regulators, I found one that worked. Now I'm full steam ahead at normal operating temperature. Well ok maybe not full steam, that pesky overdrive comes next. Thanks again folks.


-HighMiles

Had a 1979 245DL with head gasket problem. Overheated like mad one day. Did a coolant flush, oil change and thermostat (92C) change. Car ran consistently with engine temp a needle-width below red. Not any higher.

Here's a little test. Do it when first starting in the morning and engine is dead cold. Raise hood. Remove cap from coolant tank and set aside. Watch coolant tank while starting engine.

If coolant rises and overflows the tank, especially as you rev the engine a little, then combustion pressure is getting into the cooling system. Maybe just a little. I never saw oil in the coolant or water in the oil.

Another note: If you see the temp needle drop when you turn the heater on full blast, that means the cooling system isn't removing heat fast enough. There can be several reasons for this - most addressed by the other posts.

Good Luck,

Bob

:>)

Dear overheated,

My '83 wagon has overheating symptoms like yours that I've nipped in the bud by going to an electric 14" GM "puller" radiator fan. (off an '85 Olds FWD).

Radiator is tired, coated w/ aluminum deposits from head. Water pump makes noise and needs replacement and though I have a new one in a box, I have other fish to fry.

Now there's no shroud in the way, no heavy fan clutch ragging out w.p. prematurely. I switch fan manually, just watch temp gauge and use as needed. Will automate it someday w/temp controlled switch.

Less vibration, more power, better efficiency. How does cabin heater core work?
It's a good heat exchanger too.

I'd go electric in your project vehicle. We have an '81 244 new to us, came w/ new radiator (Thailand!) and water pump installed. Awesome cooling, gauge always below 1/2. But it's gonna get electrified too, it really simplifies things IMHO.

Frank

No oil in the coolant, no antifreeze in the engine or exhaust? All sparkplugs look the same? I do not think you have a good case for pulling the head yet. I would pull the water pump to look it over. Had an 83 that had a pump with a bad shaft or something and the impeller rubbed on the block, really hurting the cooling performance. A new pump had the proper clearance and fixed the problem.