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MG Midget and Sprite Technical - A series cooling diagram

Hi
does anyone have a diagram of the internal engine cooling routes? I'm in the middle of cleaning up the frogs engine and on removal of the small brass water tap from the engine block I found about an inch of rust, I've cleaned it out and tapped the thread clean and it looks like I've cleaned out to the bottom of the recess but looking to see where in the system this connects to internally to the cooling system. On blowing air through the cooling holes on the block I did get clouds of dust coming out of every other orifice but the one at the bottom of where the tap goes is obviously still blocked.

Many thanks

Alan
a reid

How this? Some of the 'outs', are leaks of course. lol. ;).

Lawrence Slater

I found old battery acid did a very nice job of cleaning the block water passages. I put an old water pump on and plugged the outlet, covered the top of the block with vaseline then filled up the water passages and left it overnight till it stopped bubbling, the result was nice clean water passages. Rinse thoroughly afterwards.
David Billington

Thanks Lawrence - not quite as helpful as I initially thought before I clicked the image link :-)

David, I opted for filling up the water tap passage with vinegar to see if it will at least let me see which way the passage turns so that I can start cleaning it out to meet up with the rest of the cooling passages as currently it goes nowhere..

Alan
a reid

Sorry Alan, I couldn't resist.

I looked on the web for a coolant flow diagram, I'm surprised there doesn't seem to be one.
Lawrence Slater

where's young Nigel when you need him?
Jeremy Tickle

Yes me too Lawrence :-) I did eventually find something in the archives which suggests that ?maybe? the Engine block drain tap passage is a straight run into the main cooling passages - can anyone confirm or deny this? if its straight at least I know I can go about it with a drill as I've been working on the premise that it has an elbow at the bottom of it.
a reid

Yup it is. I cleaned mine. The passage runs the length of the engine block alongside the cylinders. You can poke a wire down through the block, and a wire coat hanger into the tap drain hole, and the 2 intersect.

But you can't quite get a wire coathanger along via the water pump hole to the tap, because number 1 cylinder gets in the way. -- Although if you have a flexible enough wire, that's also strong enough you may get lucky.

Actually my water flow diag isn't so far out.

Lawrence Slater

This is what I got out of my block with a wire coat hanger, prior to filling it with cola and leaving it for 24 hours.

Lawrence Slater

Thanks Lawrence,

it took a few reads to get it in my head and a doodle, (image attached).

Last night (before I read your message), I attacked the drain tap (1) with a 6mm Hex shank wood drill with the point broken off and very gingerly used a cordless drill at low speed to work out some more of the crud. After getting to what I thought was good metal I stopped only to find that (about 3? inched in) there was no way the drain passageway would intersect with the horizontal cooling passage. I then started working with the drill through the cooling hole (1) to see what crud could be removed. It was mostly thick rust and just as I was about to give up, again at very slow speed and not a lot of pressure) the bit caught and hey presto I broke through to the drain tap passage. This unfortunately seems now to indicate that I have as much if not more crud to try and clear from the horizontal cooling passage as I'm assuming that it should all be to the same (ish) depth for the entire run.

Many thanks
Alan

a reid

That sounds like it was well and truly clogged up Alan. Did you have it running before? I'm guessing it must have been overheating a fair bit.

Your drawing looks about right.

Pity I didn't take pics, but as it happens, I still have that block stripped ready to build. I'll see if I can get any useful pics of the cooling passages from it.

Lawrence Slater

Thanks,

hmm last time it ran was in '94 before being laid up in the parents garage (until about 2 months ago when I retrieved it). It was stored drained and seemed to be running fine way back when with no overheating issues.

Maybe before I go too far a more important point is - 2 of the stud holes have holes through to the cooling passages, i.e rotted through. Is this game over? can I get inserts put in to give me a water tight seal? or with the stud in does it not matter?

Alan
a reid

Arp stud sealer
mog

Looked at my block again. Nothing useful to take a picture of.

I did measure the depths though. -- 1275 engine.

From block face at the drain tap, it's 3.25 inches deep into the water jacket. I poked a wire into the hole wih the tap removed, and that's how far it goes in.

From the top of the block down to the bottom of the water jacket, it's 4.5 inches. I poked a wire down one of the holes in the block and that's how far it goes down. The bottom of the tap hole sits at 4.5 inches down from the block face.

I reckon what's happened is that where your engine sat for so long, as the fluid dried out, all the solids congealed at the bottom of the water jacket, no doubt along with rust, until it solidified.

You need to soak it with your favourite soaking agent, to disolve all the crud. Screw the studs in where they've penetrated the jacket and seal all holes except the water pump opening. With the block on end, fill it up and leave it to soak. As in my pic.

I used coke, but maybe you need something more aggresive, such as the battery acid already suggested by David.


Lawrence Slater

Thanks Mog and Lawrence - at least I know have a plan

Alan
a reid

This thread was discussed between 11/07/2015 and 14/07/2015

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