MTFCA Forum

I needed to drain my radiator and now that I refilled it the petcock is dripping. The car has an original radiator and the petcock seems loose. Any tricks to help with this or is it off to the radiator shop?

Loose where it threads into the rad or loose in the valve that you open and close?

If 'loose' in the valve:

Try removing the petcock from the radiator, dismantle it carefully, and clean it thoroughly to free up moving parts. Sometimes it is just 'sticky' and the spring is not strong enough to seat the tap properly. You may just need to tighten the nut to increase pressure on the spring or install a new spring.

Reassemble, reinstall and see if the leak is finished.

If still leaking, disassemble and here it gets interesting with many points of view.

I usually start with some paste such as a fine grinding/ cutting paste. Apply to the petcock, insert into the body and rotate to bed the two together again. Don't put much pressure at the start when pushing it in as this will just squeeze out the paste before it 'works'.

In a worn petcock I have wrapped a fine sand paper (1200 grit) around the tap and then ground that in the body, reverse the paper and repeat (so that you clean up both the petcock and the body. Then repeat the paste option.

Don't 'sand' with an 'in and out' motion as that will create low spots and make the leak worse, it gets best results when done rotationally.

In the states, there is no nut to add tension, just a cotter pinned spring.

I like your honing ideas. I start with tooth paste.
Lapping compound can be too aggressive & seat the valve too deep.

Hi Ron,
I have found Timesaver works great to lap the taper on the valve. Use a socket the handle fits in & use a drill motor to turn it. There is a
heavy valve grease that works great for keeping them working for years.
Craig.

In the states, there is no nut to add tension, just a cotter pinned spring.

Good point I have a mix of Ford and Morris cars (Canadian and UK), easily mix them up... but the theory is much the same.

Use a socket the handle fits in & use a drill motor to turn it. There is a
heavy valve grease that works great for keeping them working for years.

Yes, a heavy grease lubricant really helps to seal. Good tip with the drill to turn it.

The easy answer is to fit another petcock. They are the same as those on the pan that are used to check the oil levels. Otherwise, follow Adrain's plan.

Not all Ford petcocks have a spring, washer and split pin to hold tension on the rotating piece. The early cars had a machined washer and a fancy set screw which was threaded into the end of the same piece. When the taper in the petcock body wore, the rotating piece could vibrate open easily. One on the pan of my 1912 van did just that, leaving a 100 yard trail of oil the stop at our clubrooms. Had it opened 25 miles earlier when i left home, it would have been a sad tale.

Allan from down under.

Allan wrote: ↑

Sun Mar 26, 2023 8:51 pm

The easy answer is to fit another petcock. They are the same as those on the pan that are used to check the oil levels. Otherwise, follow Adrain's plan.

Not all Ford petcocks have a spring, washer and split pin to hold tension on the rotating piece. The early cars had a machined washer and a fancy set screw which was threaded into the end of the same piece. When the taper in the petcock body wore, the rotating piece could vibrate open easily. One on the pan of my 1912 van did just that, leaving a 100 yard trail of oil the stop at our clubrooms. Had it opened 25 miles earlier when i left home, it would have been a sad tale.

Allan from down under.

Allan
I did not know petcock is the same as the ones used on the oil pan. In my opinion fitting a new one is the way to go. Thanks.