Engine Coolant Drain Plug Stuck

geordie · Apr 11, 2005

I need some ideas guys. My engine drain plug must be fused to the block. I've snapped one easy out, drive in type, trying to get it out. I managed to remove the reminder of the easy out with a Dremmel. I tried again to remove the plug with a left handed thread easy out and I think that I am close to snapping that one. I used penetrant oil and heat.......nothing. I am starting to think that the PO might have epoxied the plug in for some reason.

My alternatives seem to be:

1. Dremmel as much as I can of the plug out, and then try and collapse it. Problem is, if the plug threads are fused together then I can't see how I will be capable of collapsing it.

2. Drill out the old plug and retap the hole and fit with a larger plug. Any suggestions on thread type, tapered hole/tapered plug or straight hole with tapered plug.

Which alternative should I go for, or does anyone have any other bright ideas.

krash kendall · Apr 11, 2005

geordie said:
I tried again to remove the plug with a left handed thread easy out and I think that I am close to snapping that one.

2. Drill out the old plug and retap the hole and fit with a larger plug. Any suggestions on thread type, tapered hole/tapered plug or straight hole with tapered plug.

Which alternative should I go for, or does anyone have any other bright ideas.

The threaded easy outs are impossible to get out if you break them. Try drilling it as close to the minor diameter of the thread size as you can (or use your dremel). If you get it reasonably close to center you can get remaining threads of the plug out with a sharp pick and then clean it out with the original tap size.

geordie · Apr 11, 2005

Sounds like a plan. Does anyone know what the original 302 engine drain plug female thread size was. It looks like 1/4 inch NPT taper with a straight plug but I didn't think that this was a preferred solution for sealing. I thought that the right way was a stright hole with a tapered plug.

D.Hearne · Apr 11, 2005

Just me, But I've never been able to remove any coolant drain plug from a Ford. Next time leave it be. And good luck on getting the remainder of the old one out.

paintballtommy · Apr 12, 2005

D.Hearne said:
Just me, But I've never been able to remove any coolant drain plug from a Ford. Next time leave it be. And good luck on getting the remainder of the old one out.

what he said. i was never able to get mine out of an old 289 either. worst case scenario. drill it out a size larger. tap and helicoil it. should solve your problem.

65ShelbyClone · Apr 12, 2005

The problem is using an iron plug in an iron block. If you get it out, replace it with brass or stainless.

geordie · Apr 12, 2005

Thanks guys. Good tip on the use of a brass or stainless plug, thanks.

A machinist work colleague has advised me to drill out the remainder of the plug using the correct drill for a 1/4 NPT tap, which is 7/16 inch. If I can get the drill centered than this should bring me to the minor diameter of the block thread. Then re-tap the thread. Now this is the bit that's confusing me. Re-tapping the thread is going to cut a new thread which is unlikely to follow the original thread, so as far as I can see I'm going to end up with partial threads, if the rest of the plug falls out. I can only see this working if I tap the thread deeper than the old one, into new block iron, which will draw the plug in deeper, taper thread remember.

Does this seem sensible? Comments please, I really want to get this straight in my head before I attempt a repair.

Per the previous comment about helicoils. As the block is iron, I assume that I would only need to use a helicoil if I wanted to use the existing plug size.

krash kendall · Apr 12, 2005

You can't helicoil a tapered thread (as far as I know). When you drill out the minor diameter you should be able to peel the remainder of the plug out.

66HertzClone · Apr 12, 2005

If I were you I would install a 1/4 radiator petcock in the block after you get the original plug out. Sure makes service in the future very easy to do.

D.Hearne · Apr 12, 2005

One way to get the remainder out is to use a cutting torch. It'll burn out the steel leavings and leave the iron alone.

geordie · Apr 12, 2005

Plan for tonight is to buy a 'yellow' (hotter flame) tank for the propane torch. Heat the heck out of the plug in hopes of burning whatever crap, rust etc in in the threads. Try and locally cool the plug and give it one last go with the easy out, being careful not to snap it.

If that fails, drill out as much as I can of the plug and see if I can pick out the remianing plug threads.

I that don't work, drill and tap the hole the next biggest size for which I can get a stainless steel pet **** or plug.

geordie · Apr 15, 2005

The plug is out!

Carefully applied more heat last night and then literally dripped ice water on the plug itself. I was then able to remove it with a left handed 'easy out'.

I then cleaned out the threads with a thin rotating wire brush using my drill and ran the tap down the thread.

Thanks for the advice guys.

krash kendall · Apr 15, 2005

Good job! It's quite a relief when something like that is over with.

Engine Coolant Drain Plug Stuck

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