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I still have issues with my 903 Coupe Roadster overheating in stop and go traffic on warm days. Can someone with a 903 measure their fan? We questioning whether I have the correct fan. I have no trouble with cooling going down the road.

My dimensions on my 6 bladed fan are:

Blade length 7"
Blade width 3.5"
Pitch 1.5"
Distance between blade and radiator 1 3/8"
Blade distance from edge of radiator 1 1/2"

Also please note radiator has been recored, water jacket replaced and engine rebuilt from top to bottom. So we are chasing now airflow at low speeds as a possible cause for the overheating.

Dear tbird:

That doesn't leave a lot of possibilities left.

Make sure the shutters are fully open. Probably are because the car would overheat at speed otherwise.

Make sure the temperature gauge is accurate. Do you think it is running hot because the radiator level is too high?
It should be level with the top of the core.

If it is overheating then a drop of water should boil when dropped on the back of the cylinder head.

I handled a case once where the car wasn't boiling, but the radiator cap gasket wasn't sealing.

Those old motors don't have a lot of thermal efficiency and rising temperature after coast down is normal. Although a small vacuum leak will cause lean running at idle and raise the temperature. As will late timing.

Finally, one thing Turnquist was crazy about was not overpainting the radiatior core.

Measured and correlated temp gauge.radiator level is not too high. Hood handle is to hot to hot to handle with bare hands

On the exhaust side, those handles will get very hot, especially the 10th and later series cars because they are right next to the exhaust pipe. The earlier cars had the handles outside the hood.

One thing I have seen is tight pistons causing heating problems. If the motor turns over very slow when hot there may be a clearance problem. Modern pistons need wider clearances than the old Packard stuff. Around .002-.0025.

I'd also check the motor vacuum. I dealt with a brass car that boiled over while I watched. It had a manifold leak.
After I fixed that the extra vacuum made it smoke like crazy because the rings were shot.

One thing about those updraft carburetors is they can start to vapor lock and run lean during idle. I would try richening the idle mixture to see if that cools the motor. Parades are a great way to get old cars to overheat, so if the gauge isn't going solidly into the red it may not be running hot.

There is also the possibility that the block has eroded behind the water pump impeller enough to inhibit flow at low rpm. Raising the idle speed would test that.

Had a similar problem on a '32. Did all the usual things mentioned and nothing helped.

Finally pulled off the water pump and put three dime size pieces of modeling clay on the back of the impeller.

Reinstalled the impeller, with gasket, and torqued it down.

Removed the pump and measured the thickness of the clay.

I had about .080" clearance from the back of the impeller to the flat casting face on the block.

Then machined up a copper disk, removed the impeller and soldered it to the back of the impelled. Machined the disk so I had .040" clearance.

after installation I measured a 10 - 15? drop in top tank temp. after 45 minutes, at idle, just by doing this.

If you have the original style honeycomb radiator you may try back flushing it with air using one of the water / air flushing tools made especially for this job.

For those who don't know....never ever put Bar's leak or any other sealer in a honeycomb radiator. Surest way to plug it up.

The radiator has been recored with tube/fin style core.

Well, that is a pretty good example. A good epoxy like West Systems G-Flex or solder (out of car) could also be used to fill the pitting in the block.

I don't recall if the 9th series used any tubed radiators, but 10th series was tubed. 8th series was all cellular.

And of course in later series they used both. Rolls was using cellular right into the Cloud series. In a clean system I like the cellular radiator.

Great suggestion by 32model901, even a small amount of excessive impeller clearance in a centrifugal pump results is very large losses in pump discharge volume. The same principle applies to the fan blade to radiator distance.

Ken,

Have you done a flow test on the radiator? Even if newly cored, there may have been a mistake made. Unlikely, but an easy potential problem to eliminate.

Tom