VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1916-1922 - Model 490 Radiator issue

Got the 490 out today and took her for a spin. Whenever I stop the car some antifreeze comes out of the overflow. Once down to a certain level (none visible looking in the filler neck) less comes out, but I prefer to run her with enough coolant! Is this happening because there is no expansion tank on old cars?

You do not find an expansion tank on your car, but you have a water pump which could press water out of the system. If you see air bubbles coming up from the filler neck when the engine is running, it also may happen that your engine head gasket is not doing the job and need change to a new one. If the bubbles are coming for some time after stopping the engine, I think you have a leakage near or in the head gasket.

I would imagine you get more replies here in the next day or so.

In my opinion the answer is yes. I use to fill coolant up to a level about 7-8 centimetres (about 3") under the top of the filler neck. Everything above that level always disappear through the expansion pipe (?) as the engine gets normal working temperature and the coolant expands. At that level I can drive 300 kilometers (500 miles) without filling coolant. If it is very hot weather I check more often. If I stop the car and let the engine run for a while, of course the engine temperature rises and more coolant disappears, and I have to top up. Also I check more often if it is very cold weather. I have noticed a couple of times that the temperature gauge on the radiator shows normal temperature, despite the coolant level is far too low. I believe that at certain circumstances the temperature gauge is more influenced by the cold air streaming through the upper part of the radiatior than the hot coolant from the engine. But I don´t know for sure.

If there are bubbles, I would check the water pump packing first, If a bit loose they can suck air when running, then the impeller makes the coolant foamy and it will overflow. As long as there is some water in the upper tank, it should be ok. It doesn't have to be up to the overflow tube. I find fill it up all the way, run it and let it puke till it quits then run it some more and check the level, but don't add any unles you know it is way low. You can acually check the level when the engine is off by feeling the radiator front and tank inside the eng compartment. They tend to find their own level they like to run at. Now if you run it too long at retarded spark they will get too hot too fast and sometimes boil water out. Also, I would double check the tightness of the head before replacing the gasket, sometimes they just need to be tightened up and those copper asbestos gaskets can take that unlike modern ones.

On a related note, I bought a new "Junior Motometer" and mounted it on the cap. I see no red in the glass when cold. Drove it a few blocks and still nothing. How hot does it need to be for the red line to show up?

I have to drive my 24 about 20-30 minutes to get the red showing.

Hi Guys,

I put an expansion tank on my 28 Tourer about 20 plus years ago, best thing I ever did. I keep my coolant right up to the top of the filler neck. Only need to top up the system about every 4 to 6 months.

Cheers

Ray

The easiest weay to check if your motometer is working: Put the brass end under a hot water tap for some few minutes. The red will come up, for sure. If not, it is damaged. I have given the advice to many on eBay for them to find out if the meter is good or not. The thermometer in the senior meter can be replaced, but the junior they do not have spares to, so you have to buy a complete new one.

Today I took her out for a longer spin, about a 20 minute stop and go drive, 80 degree day. The red just started to appear at the bottom of the tube. I Guess the motometer is working and she's not running particularly hot.

Ray,

Where did you put the radiator overflow tank? Can you post a picture or two? I want to install one on my '28 Canopy Express.

Thanks, Dean

The overflow tank hangs from the center support rod in my '28 Canopy Express. Actually it can be anywhere but best as high as you can get it.

Thanks for the info, Chipper.

I'm thinking of using a small vintage fire extinguisher (brass from the 1950's) as the overflow tank and mounting it as high as I can on the firewall (passenger's side).

Cheers, Dean

Hi Dean,

I fitted the overflow on the engine splash tray, where the oil filter would normally be, and I disagree with it being positioned as high as you can make it.

Mine has run like this for over 25 years, works fine.



Cheers

Ray

Hi Dean,

For a more detailed account of the installation, please see the link to the posting on my blog


http://my28chev.blogspot.com.au/2011/09/improvement-no-6-done-in-80s-radiator.html

Cheers

Ray

On most modern cars the overflow tank is vented to the atmosphere, no pressure cap and mounted high.

The tanks are mounted high so that as the coolant cools and contracts you do not have such a long lift to refill the radiator .

The low mount tank system shown above as I see it is pressurizing the coolant and pushing it back.

I myself would be reluctant to add pressure to a stock 490 cooling system.

Hi Parts N Junk,

The overflow tank I installed is VENTED to the atmosphere by removing the rubber washer from the radiator cap on the top of the tank, and with a rubber washer sealing the dog bone cap, the water is SUCKED back into the radiator NOT FORCED.(Refer to point 3 on my blog posting)

I have no experience with a 490 cooling system, but I do know it works well on a 28 and has done for over 25 years.

Cheers

Ray

1928isgreat

I did read your blog and you estimated your tank has 1 or 2 pounds of pressure.

Your success may be due to your installing late model water pump seals. On a stock 490 there is just as much chance of sucking air through the water pump packing as sucking water from a low mounted tank.

I agree with Chipper, mount the tank high reduce the lift.

Hi Parts N Junk,

The overflow tank was run with a standard Chev 4 water pump from the 80's till 2009 when the modified pump was fitted. Prior to this I always maintained the original water pump to ensure coolant leaks were the exception and not the norm.

My reference to sucking is descbibing the process of hot water expanding, cool water contracting.

If the water pump on a 490 has a bush and packing arrangement that is less effective than a 28 or in poor condition your concerns may be well founded.

I think the subject also strays into the area of how well you maintain your engine.

But you have me curious now, and I will read up on a 490 system.

Cheers

Ray