Datsun Roadster Forum-311s.org

I'm working on a customer's 1600 67 Roadster that's been modified (not by me) to bypass the heater core. I ultimately want to flush the radiator and the block. When the car arrived for service there was no thermostat in the system. The upper and lower radiator hoses were in place, as were the tube running through the intake manifold toward the firewall and the tube below the heat shield. The two metal tubes were connected with a short 3-4" piece of hose near the firewall, but beyond that, the tubes had been plugged/crimped. I installed a 180 degree thermostat and drained and refilled the radiator with distilled water 3-4 times. With the thermostat now in place, the most I can get in the system is about 1/2 gallon with the thermostat closed. When the engine is run for 5 minutes it will take a little more when the thermostat opens. So here are my questions:

- How much water should be in the system when full, absent the heater core?
- How can I be sure the system is full without removing the thermostat?
- How can I be sure water is flowing throughout the block and the rest of the system with the thermostat in place, as the car is currently plumbed?
- Can I backflush the system through the lower radiator hose?

I don't have easy access to the drain plug in the block itself. The temperature gauge is not currently operational so I have to use my IR meter. Obviously, my goal is to return the car to the customer knowing the motor will not overheat, causing bigger issues.

Your thoughts are much appreciated!

I can’t say what the capacity would be but I would expect to be at least a gallon, more likely a gallon @ a half.

The OEM thermostat has a hole in it to allow air to escape but I generally push the thermostat open & put an aspirin in to hold it open while filling. You might try pushing the thermostat open from the filler neck.

You also might be able to fill the block from the lower hose, then the radiator using the upper hose.

Good luck.

Peace,
Pat

I would say subtracting 1.5 litres for the heater core/hoses will put you in the ballpark.

As for flushing the system, I would really try to use both drains (rad & block) - Just flush the system with a garden hose until it’s coming out clear from both drains.

Your wanting to touch a 50 yr old cast iron block drain ?

A fill funnel and using it with the car on a incline will get it full of coolant , the weep hole thermo ( most all.have works )
A hot upper hose and not as lower hose or inflated temp gun will.tell you it's fine lowing
If anyone is still pulling radiator s apart if it hasn't been apart lately best to have & rodded out

redroadster wrote: Sun Jun 26, 2022 9:09 pm Your wanting to touch a 50 yr old cast iron block drain ? …

Why not? I’ve had two (worked on more) and they always came out when I flushed the system and changed the coolant … some requiring a little more finessing, wd40 and patience than others. If you destroy the petcock, you just replace the whole thing with a BSP brass plug.

Since he’s having some serious overheating issues and can’t get much coolant into the block, it seems to me if he wants to do the job properly, he at least needs to give it a shot. There can be a whole lot of crap in there plugging the passages every time it’s circulated if not cleaned out every now and then. Of course, I’d get the clients go-ahead first because of the added risk/cost …

Because your more going to stir it up.rather than flush it clean out IMO and machine shops say this , except newish Toyotas ,I'd just leave it ...some plugs start to leak later have had that happen I've see much muck at the bottom.of the block rust particle that clump.there and stay put .