Radiator question - what am I missing?

[Series3Scott]

When it rains it pours I guess - got my brake MC rebuilt and installed. Put in the new clutch MC. Installed new flexible brake hoses. Car is back on the road again but now I'm dealing with a persistent leak at the drain plug of the radiator.

The guy that rebuilt my radiator almost 14 years ago installed a modern plastic drain plug so I took this opportunity to order the correct brass one from Rick. Arrived in the mail and went to install it and quickly realized the fine thread of the brass petcock would not work on the obvious course thread of the radiator. Crap - I guess they tapped it for course thread when they did the 3 core rebuild. Figured out it was a 3/8" course thread so pulled a correct bolt from my stash and installed, but still leaking.

What am I missing? Wouldn't a simple bolt work? Maybe wrap the threads with some thread tape? Would they have used a pipe thread?

 

[mikephillips]

First, is the bolt you used loose or tight in the threads before you snug it up, meaning, can you feel a little side to side motion if you try to wiggle it?? If so it's a bit to small and can leak around the threads. Second, have you cleaned the surface off around it to be sure it's from the drain itself and not perhaps a crack or pinhole where the drain collar is fixed to the bottom tank?? If not, do that as well to be sure you're dealing with the proper location.

As for a fix, you can get different sizes of drain taps. I've seen some that look exactly the same as the supplied brass ones at local plumbing supply stores, wouldn't be surprised if that's where our suppliers source theirs. You can see if you can get a course theard version that way. You can also get fiber washers to use between them or a bolt and the tank to act like what the oil pan drain washer does. I'd guess teflon tape around the threads would help too.

 

[Bill Blue]

Or try an O-ring of the appropriate size on a coarse threaded bolt.

Bill

 

[DanR]

What did you do with the "old plastic plug"??


Take it (if you still have it) with you when you go to look for a new one.

Getting the threads per inch and dia will give you all you need.

 

[Series3Scott]

What did you do with the "old plastic plug"??


Take it (if you still have it) with you when you go to look for a new one.

Getting the threads per inch and dia will give you all you need.

That's the first thing I did - took it to Autozone, Advance Auto, and O'Reilly's and nobody had one that matched. And of course you can't tell them the make and model because it wouldn't matter.

I'll go back and wiggle it around a bit to see if perhaps it's an actual pipe thread vs. course thread but I don't recall it being loose. I'll check the plumbing section too and try the 0-ring idea with some teflon tape. Tried crushing two rubber washers and a regular washer up against it with the bolt but that's not working either. Grrr.....

 

[PROCRAFT]

bolt

You need a crush washer either alum or copper!

 

[Mike snyder]

I think there are two different kinds of drain plugs for the alpine. I seem to remember ordering a brass one with fine threads from SS and not having it fit and then ordering another in plastic with coarse threads that was the right one.
Mike

 

[delta5]

radiator drain plug problem

To the person having a problem with their drain plug, I had the exact same problem with the one I ordered from VictoriaBritish...the plug is improperly threaded and will not work properly. crapppy supplier I guess.
I too am thinking of using a copper washer to seat properly....went and looked at another Alpine radiator and that one was just a plain old bolt so it seems other options have been used

delta5

 

[Series3Scott]

My Series 3 is back on the road! Thanks to the copper crush washer and 3/8" bolt I was able to seal up the radiator drain hole.

Rebuilt brake master is working great, as is the new clutch master. Bled the systems, took the hardtop off, and drove the kids around for 2 hours today on the winding back roads. Stopped at Sonic for slushies and my daughter, sitting across the "back seat" complained she couldn't find the cup holder. I told her it was next to the USB port.

Sweet!