my 29 U

[Glenthechippy]

Hi guys.
Can some one tell me in detail how the overflow from the radiator works.
Ive just had the radiator rebuilt and it isn't pressurising while the engine is running because of the overflow pipe inside the radiator isn't capped off.
I can only imagine that there is a piece missing in my puzzle.
Any help would be great. Thanks

[chetbrz]

If you have a 29 U you do not have a water pump.  The cooling system works on a thermal-syphon principle.   The system is not pressurized.   Basically once filled with coolant the coolant will expand to a working level while driving and eject the unnecessary amount of water.  It is normal to open the radiator cap and not see any coolant when the engine is cold.  Literally while running.., the engine boils out the water and cool water from the bottom of the radiator flows in and the process repeats.  Due to the large size and positioning of the radiator this system works extremely well.  Pressurization started so that the radiator could be made smaller to facilitate more room in the engine compartment and hotter running temperatures for better combustion.

You can tell that the system is working by feeling the very upper section of the radiator and it should be hot while the bottom section should be much cooler.   BTW... once you top off the radiator don't put more coolant in and you should be OK unless your radiator and system is clogged with rust and debris.

Welcome to the Forum,
Chet...

[SteveG]

Chet is right on the money.

Like you I was concerned with the over flow whenever I filled the radiator, 'till I found out about what Chet was talking about.

When I first got my car I removed the engine side of the top and bottom hoses, then hosed inside of the block and radiator. An amazing amount crud was removed. The engine runs cool, even in 95 degree ambient temp.

SteveG

[Glenthechippy]

Thanks Guys.
Clearly the piece i have missing was "Knowledge"
I love this Site. It has helped me a lot.
I knew about the thrmosyphon system and the fact it had no water pump but it did scare the begevers out of me seeing water ejecting out and once cooled not seeing water in the radiator. The radiator has just had a new honeycomb core fitted in it in New Zealand. So understandably I'm paranoid about hurting my baby.
These replies have helped me no end. The bloke that rebuilt the car (my fatherinlaw now passed) put a temperature gauge in the top radiator hose. I now wonder if that would be the best place for it ? The gauge was showing 170 deg for about 10 min then dropped down indicating no water flow. Is it a better idea to remove the thermometer and just go with the "feel with hand" system. i am just using Water in the system at the moment. What additive,if any, would you recommend in the cooling system. I live north of Sydney Australia so freezing is never a problem here.

Thankyou Chet for the precise answer I was after and Thankyou Steve for the confirmation. I(by nature)try to get a second opinion on questions and to get two answers in one hit was wonderful.

Glen

[chetbrz]

Glen,

I would think that the bottom radiator hose would be better place for a temperature sensor.  The top radiator hose doesn't have constant flow. Here again more like water boiling out of a teapot. I am slightly concerned by the fact that you said the installed gauge drops out for a long period but if the lower half of the radiator is cool and no steam you should be OK.  Cars of this era used a motor-meter which was a temperature gauge installed in the radiator cap which allowed the driver to view it from the driver's seat.  The problem with the 29 Plymouth is that you can't open the engine compartment doors with a motor-meter mounted in the cap.  Not a big deal as long as long as you remember this. 

I also had these same concerns when I first start driving my 29 so I purchased a rather expensive repro cap and gauge from J. Fisher.    As Steve pointed out, after a couple of years driving this car I have become very comfortable with the performance of the thermal-syphon system.  See below my current radiator cap.  The front side has the Plymouth emblem and the side facing the driver shows readings for cold, normal, and steam.  This was not a Plymouth option but was a normal add on for the period.



As far as your second question I would use some mixture of antifreeze that has a rust preventative added.  Most general anti freeze products have this.  Just my 2 cents...

BTW... Steve's suggestion about flushing out as much debris from the motor and hoses is a very good one.

Let us know how it goes,  Chet...

[Glenthechippy]

Thanks for your help Chet.
I love the radiator cap. I would love to find one of those somewhere.
I don't have a plymouth radiator cap so I'm still searching.

I better head back down to my shed.
Cheers
Glen

[imoore]

G'day Glen
Welcome to  the forum. A little of topic but who Re cored your radiator. i am in need of getting this done soon. would be easier to send to NZ than USA if i had to. There is a place in QLD but i think his prices are way to high in my opinion anyway.

Ian