Datsun Roadster Forum-311s.org

Linda wrote: ↑Wed May 08, 2019 10:20 am You might have a fair amount of muck in the block. It is not guaranteed to be flushed out with a regular coolant exchange.
Also not sure if your cap rating is correct, I thought it is supposed to be lower....like 7 lbs
Linda

You are correct about the cap rating. With a 7lb cap, I seriously could not keep the coolant in the car and i ended up running dry several times so in went a higher rated cap which so far has kept (most of) the coolant in the engine where it belongs. If I can ever figure out how to get the car to run cooler, I will definitely go back to a lower rated cap but for now, im going to leave the higher pressure one on.

I wonder if anyone ever figured out a way to drain the block, let it dry out then use a flexible vacuum wand to suck up as much of the rust as possible.
I think I would check to see if PO ever cleaned out the block.
Would a higher rated cap push coolant out somewhere else?
Linda

Old hot rod fix. Drain system. Fill with at least 1 gal of white vinegar. Run until hot let it sit overnight.
Drain and flush thoroughly.
Dan

So far the hoses seem to be holding up. The main ones were replaced but the heater hoses are... Who knows. Otherwise, no other leaks to report.

greydog wrote: ↑Wed May 08, 2019 11:21 pm Old hot rod fix. Drain system. Fill with at least 1 gal of white vinegar. Run until hot let it sit overnight.
Drain and flush thoroughly.
Dan

When I did my flush I used two different chemicals. One that is supposed to be for rust, the other for scale. Ran distilled water through everything then filled with antifreeze. I looked at vinegar but thought it may not be safe/I don't have the ability to use pressure to flush it all out. I think it may be wise to figure out a way to just blast some fluid through everything

Don't trust a 50 year old sending unit and gauge 100%. That system works by reading resistance which changes as the sending unit warms up. But...there can be new and wonderful resistance other places in the wiring I bet.

Trust the IR thermometer "gun." Shoot the radiator and thermostat tower - those are the temps that matter.

Also, if you ware worried your water galleries in the block are scaled up you can use something us boaters use called RidLyme. You use a bucket and a pond pump connected to one of the hoses to circulate the ridlyme through your system and back out to the bucket.

HTH
James

oh! that is a fantastic idea using a pond pump! I will definitely look into this.

Should we be concerned that the 7lb cap didn't keep coolant in the engine? Head gasket?

I had this happen to me with my 66 1600 in college Greg. I changed the head gasket and still had coolant dumping out at the bottle/cap. I changed the cap and problem solved.

If the oil isn't milky I would not suspect the head gasket.

James

Okay so here is the current situation, I dumped out the fluid I had and replaced it with distilled water so now its about 75% water, 25% antifreeze. When doing this, I re-checked the thermostat housing bolts, re-torqued the headbolts to 50ft-lb. About 3 of them gave a little so that was probably a good idea and did the valves while I was in there. Discovered they were wayyyy too tight. I couldn't find a feeler that could fit between the rocker and valve and gave up at around .008. Engine was cold so set to .020. I jacked the front of the car until fluid came out the thermostat then started burping and found out the thermostat cap was leaking. fixed that one, put the 21lb cap on the radiator and a new 9lb on the overflow tank.

Did a long test drive and the car stayed around 200F with ambient temps at 75F. I hit some stop and go and the car just hated it. Couldnt accelerate past 40mph, sputtering, etc though engine temps stayed the same (checked with gun). Fan was running fine and everything else looked okay. So i decided (against better judgement) to hop on the highway and see if better airflow will help and sure enough, after just a quarter mile, the car seemed perfectly happy again and pulled strong/etc. I will have to figure out what is going on there later on but as of right now, I think the block temps are under control and fluid is staying in the car.

Check the ground at the temperature sender and the voltage from the instrument regulator.

200 is about the correct temperature for your engine.

If your champion radiator has a fill on it, it could have the wrong cap. It is should have a cap like your tower without spring....Not a pressure cap.

Mine is an eBay knockoff of the u20 champion. It had a pressure cap. That's good to know about the cap but I think with a 20lb cap, it will be fine. I'm not sure a standard cap will fit with how the fitting was designed

Do you have a fan shroud to help pull air through the radiator when you are not going fast?

I use an electric fan, the OEM shroud is long gone.

I am continually amazed at overheating problems with our cars.

Eliza ('70 1600) is running a stock radiator (albeit recently cleaned/rebuilt) , stroked engine, no shroud, 4 blade fan, 160 thermo (I think, maybe a bit higher) and regardless of traffic, ambient temperature sits comfortably at middle range. Hard driving, (think Angeles Crest) or just sitting on the 405 contemplating my future, she never varies.

There MUST be something else. Tuning. timing, coil, plug wires - I don't know.

Would be great to find out.