MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - engine coolant drain

My comment is more of a question. I have a 74 B and I am tinkering and replacing. It was running when I started this project and did not over heat. I pulled the block coolant drain plug and it seems to be blocked! Does anyone have an idea on how to unplug it without removing the head? Didn't want to do that much tinkering! Thanks BL
BA Amstutz

This is a very common problem. The passageway, that leads to the drain, is extremely small and quickly gets clogged up. You can try to clean it out with a wire coat hangar or other small metal probe. RAY
rjm RAY

A lot of these drain plug apertures were never drilled through into the water jacket. If you really want to flush out the block, remove the water pump or knock out a core plug in the side of the block, There is often a build up of sediment around number 4 cylinder so best to remove the rear most core plug.
jim soutar

Ray, I have been digging with an ice pick. I am not sure of the direction of the passage way.
Jim, Is the core plug low enough to drain all of the liquid? Well guess i could use something to suck it out.
Thanks for a quick response. Way too cold to tinker today!
Blair
BA Amstutz

What about a soak with something first? We have a product called CLR here in Oz, it will de-scale kettles etc anything that has had water in it at boiling point temperatures. If you can fill the system or just the block with hot water,(guess it it will cool down quick) but leave it overnite with something like this stuff then drain and a good poke around? Mike
J.M. Doust

The maker of CLR says do not use it in automotive radiators.

Go to this FAQ and scroll down to radiators:

http://www.jelmar.com/faq.htm
Steven 67GT

CLR is a mixture of organic acids such as oxalic, citric etc. I have boiled carburetter parts in it. It is safe for aluminum, copper iron. I doubt it would harm the rad for an overnight soak.
Art Pearse

Thanks for the info.! Should I drill it or will i damage the block? I will remove the rear core plug and maybe I can get to blockage! Blair
BA Amstutz

If it was not overheating, don't mess with it. The drain is located at the front/bottom of a pocket at the bottom of the water jacket, and the pocket fills up with crud if not drained and flushed very frequently. It does no harm usually. You can attempt to probe it with a sharp wire, but it only goes about 1/2" or less in from the threads before you have to go up and back. Frequently the entire area around the bottom/back of #4 cylinder is full of crap that you cannot get out without the head off and the core plugs out and a lot of work, but it still rarely causes overheating trouble. I had one engine that had casting core sand baked in all the way around the back half of #4 that may have had a problem (came to me for rebuild after an engine fire); it took two days of hammering through every available orifice with custom made bent chisels to clean it.

FRM
FR Millmore

The drain hole is at the bottom of a small passage that is about 4" above it. If you can clear it out, you can drain the entire block from this point. RAY
rjm RAY

Okay, no drilling! I may dig around a bit more. I am not going to mess with all that work until I have too do some major work on the engine. Right now I am just trying to freshen things up. Looks like the front engine mounts are next on the list. Well, thanks again! have fun. Blair
BA Amstutz

I think FR has the best advice for now. :Let it go" which looks like the direction you're taking. It is almost impossible to unclog this externally. The passage is narrow and clogs easily. Mine has been clogged for 15 plus years. Just makes it hard to drain the block is all. So, I use a backflush connection if needed.

Bob McCoy
New Hampshire
Robert McCoy

REmoving core plug leaves only a small amount of coolant in the block. it is certainly low enough to get most of the crud out by digging with a bent wire the onlyway you can remove all of it is as suggested by FRM with the head off.
jim soutar

Answering Steven, quite right no CLR in Radiators. I am thinking just the block. After all, the engineers are soaking the whole block in quite caustic solutions at the shop prior to engineering work, to really clean. So if we were careful could we not use a similar soln. iinside the block, then drained adn carefully washed out/ Mike
J.M. Doust

You can easily ruin your camshaft bearings with "caustic solution". Replacing cam bearings can be a hassle in these older MG's so I'd avoid the aggressive cleaning solutions. But, that's just my opinion. Others may have more experience.

Robert McCoy

This thread was discussed between 01/02/2011 and 08/02/2011

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now