posted March 03, 2008 20:26               

Sometime ago I had to buy myself a new radiator filler neck and cap as the original neck was worn through, big hole on the side. The cap looked like it had come off a Japanese vehicle and fitted into a much narrower neck.

The neck and cap that was supplied to me was in the region of 50 mm dia. The cap also has a TR6 stamped on the one ear and 50 on the other(the two bulges on either side of the cap that help you get a grip)

Ok my problem is that water dribbles out of the overflow as soon as the temperature starts climbing, even though she is just idling at say 1600. If I place my finger over the pipe for a short while and then release water shoots out.

To me it appears that the cap is not sealing properly which is strange as it is still new. The neck is also new and to me it looks fine.

At my place of work we have a couple of Ford 2610s' and a 3600 can I try the cap on one of them and see if the same happens?

Look forward to any help please.

Kind regards
Mervyn

posted March 03, 2008 22:34               

Greetings from Holland,where the astronomical spring has started,so we got hail today...

posted March 04, 2008 12:16            

As far as I know there are two types of radiator caps available for the Dextas and all Fordsons for that matter. One is a pressurised cap with a spring and rubber seal that seals into the neck of the filler spout and the other is unpressurised and only seals on the top of the filler spout. I am not sure which way it went but I believe that the unpressurised caps were often supplied for export markets. From the description you give it sounds like you have an unpressurised cap now and you would be better off with a pressurised cap. I have no idea why Fordson would ever use an unpressurised cap for any market, but you may need to specify that you need a pressurised cap when ordering a new one. I hope this helps.

posted March 04, 2008 18:05               

Thanks for you responses. I omitted to mention that my cap is a pressurized cap with spring which is rated at 50 psi.

I noted in the specs that the cap should be a 70psi rating so I have asked the radiator repair shop to order me one.

The TR6 I mentioned in my first post should have read TRG 7 which is the 50 psi. The cap I have ordered is a TRG 10 giving me the 70 psi.

Rob I wish we could be enjoying your weather(not the hail) but moderate temps and rain, ours is horrific with temps reaching lower 40 degrees including discomfort level.

I hope my new cap will resolve the problem.

Thanks again guys, I will keep you posted.

posted March 04, 2008 18:39               

Have you slipped in an extra "0"?

Normally cap values are around the 7 to 10 psi.

Pressurisation of the radiator causes the bubbles of saturated water vapour (boiling) to form at a higher temperature from what I remember from my physics lessons many years ago. If you take the cap off, they form instantly because of the reduction in pressure and the water will shoot out of the radiator and can scald anyone in the way.

When we were doing physics, Mount Everest had just been climbed for the first time by Sherpa Tensing and Sir Edmund Hillary. Our physics master used to tell us that the temperature of the water that they boiled at the top of the mountain to make their tea, was lower because of the thinner atmosphere (less psi) than the cup they made at base camp.

Sir Edmund died a few weeks ago. Ann's old school had a signed photograph and letter from him because one of the houses was named after him.

posted March 04, 2008 19:16               

You are quite right, well picked up, it is 7psi or 0.5 bar. That information actually comes from one of your strings you posted in 2005 Brian titled "Radiator cap" Knew I had seen it somewhere last night.

Thanks for the physics lesson.

Kind regards
Mervyn

posted March 06, 2008 16:52               

On the other hand could there be something more serious causing the pressure to build. What I also noticed was that the temp did go halfway into the red when I reved the tractor up. This did not happen before when I went on a 35km trip to the weighing bridge about two years ago.

Since that trip I did have the inj. pump off timing gear cover off to replce gaskets to stop leaks. So far so good with leaks except for the former temp and leak problem.

I have not done any restoration on the engine yet as I was hoping to put her through some hard work to assess the situation. Maybe I should have done that in the first place three years ago.

Thanks for the part numbers BarryM, I may have to eat humble pie and buy a cap from the local Sparex dealer. The cap I have now is a Behr make made in South Africa.

Sorry about the long winded story. Hope someone may have some answers.

Kind regards
Mervyn

posted March 07, 2008 13:55               

Feel much better now, it was that little ding on the face of the neck causing the leak out of the overflow pipe. Had the radiator guys straighten it up. The over temp must have been a air lock somewhere. After replacing the neck adaptor I ran the tractor and the temp steadily climbed to well into the red. I then decided to massage all the radiator hoses etc and the temp came down in to the green. As a matter of curiosity I want to retry the 5psi cap and see what happens.