What do I need to know about flushing the radiator/cooling system. Whats the best/most effective way to do it without taking the radiator out? Replace upper/lwr hoses while im at it? How do I bleed the cooling system?

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1977 LEYLAND MINI SUNSHINE 'S'

Depending on how bad it is, you might need to remove the radiator, however there is no harm in trying to flush first.

Make sure you turn your heater to HOT.

At the bottom of the radiator there is a drain plug. It's toward the front of the car, and is difficult to see, but if you put your hane down there, you'll feel it. If it feels like a bolt, it will be 7/16" AF spanner.

On the back of the block, near the clutch slave cylinder there is the block drain plug. This will either be 5/8, 11/16 or 3/4" AF. It is a bit of a bugger to swing a spanner in there.

First,I'd sugget draining your system of what ever is in there, then refill with water. While that's in there, go for a drive to supercrap or some auto store and buy some cooling system flush. There are a few. I've used TK and Nulon and they are OK (I don't think any are fantastic).

Drain the system again, put the plugs back in and then follow the directions on the cooling system flush that you have just bought. DO NOT LEAVE IT IN TOO LONG or you'll be sorry.

After you have run that stuff through, drain it and re fill again with water. Drive it for about 10 mins, drain and fill again with water. This is just to make sure you remove as much of the flush as possible. So be prepared to do this a few times.

When you feel it is a clean as it will get, drain the water and re-fill with decent coolant.

These cooling systems don't really need bleeding as such, just fill it, making sure the heater is set to HOT, let is sit for about 5 mins, check and top up as required. Go for a drive say 15 minutes, bring it back, let it cool right off (overnight) and check / top up again as required. That should be it.

If this method of flushing does not get the result you were looking for, you may need to go to a radiator repairer. Some of these guys have some pretty good flushers that can work well.

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Ok thankyou. When im filling with water, flush and finally the new coolant do I fill it with a few liters with the engine off, then start the engine and keep filling till its full?

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1977 LEYLAND MINI SUNSHINE 'S'

Yes, you can do it that way. I just usually do it cold, engine off.

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If nothing comes out that block rear drain because it's full or rust/sand/whatever, pull the bottom hose off the water pump instead.

[edit] and if you've fitted a recent POS UK radiator the odds are there's no drain plug in it- they save 2 bob by leaving the fitting out.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Yeap, that''s another way.

Or I try first with a 1/4" Drill bit in the block drain. Just turning it with the fingers get a lot of crap out, but sometimes it might be chockers, in which case as the doc says.....

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Once Ive ran the engine for a short amount of time with the radiator flush in it, do I need to run the engine with clean water, run it again with clean water until all the flush chemical is gone.

Or can I just keep clean water flowing through with the engine off and the block/radiator plugs out till its all clean??

Also is premixed coolant better than mixing my own?

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1977 LEYLAND MINI SUNSHINE 'S'

I actually just did one this afternoon. When you finished with the flush, remove the plug from the back of the block and let it run out. Then put a running hose in the radiator and let the car idle. Make sure the hose is running quick. After clean water is coming out, let it run for another minute or so then stop the engine and the hose. Take the plug out of the bollom of the radiator and again run the hose in the top until you get clean water coming out + about a minute.

Replace the plugs.

I use Tecalloy which is a mix your own. It comes in 500ml containers. When I refill the system, I put about 200 to 250 ml of that straight in to the radiator, then fill with wate as normal.

Be careful with coolants as many of them have glycol which will ruin paint work if let on there, so be prepared to hose it straight off.

I drained an engine yesterday that was last filled about 25 years ago with Castrol Coolant. It has been sitting for about he last 18 years. The coolant came out 100% green and clear. No rust or crap at all. This too is (or at least was 25 years ago) good stuff.

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Cheers GT mowog. Very helpful

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1977 LEYLAND MINI SUNSHINE 'S'

Also ,not sure what your tap water is like over there? It's crap over here.
We buy distilled water(its cheap) and refill with distilled water.

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We've got tank water. Distilled water is a good idea though. Good Tip

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1977 LEYLAND MINI SUNSHINE 'S'

Tonight I had an hour free for the first time in ages so I decided to flush the cooling system.
Drained the radiator and about 1 1/4 liters of coolant came out. Then took the plug out of the block expecting it to drain.

After I unblocked it nothing came out. So I pulled the bottom radiator hose of the water pump and tiny bit trickled out.

I think all up 1 1/2 Liters came out.

Could there be more in there that cant drain out? Maybe in the heater? Or maybe it used some water coming home last weekend?

Any help please as Im not 100% in the know....

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1977 LEYLAND MINI SUNSHINE 'S'

Did you look to see if it was full (or near) before you started?

These systems hold about 3 1/2 litres-ish.

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It wasn't full. Actually I couldn't see any coolant in the radiator when I opened it.
Maybe there was only 1.5L in there? How could this be? Would have it used 2L coming home from Yea to Bendigo? It didn't overheat coming home nor did the temp gauge move anywhere near the N.

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1977 LEYLAND MINI SUNSHINE 'S'

Well in all fairness, if you couldn't see any in the raditaor then we would know how much was in there to start with, so it could have only been 1.5 litres or so.

If it was quite low, the temperature gauge won't work at all properly because the sender (that sences the temperature) would have been in air and not coolant Air is a very poor thermal conductor so it will always show cool / cold.

Before you try flushing, I would suggest making sure you can get coolant / water out of the block drain and the radiator drain. For the flush to work at it's best. it need to be able to reach as much of the cooling system as possible. If it is that blocked up, it may not get to where it needs to and so won't clean, and you could actually end up in a worse position with hot and cold spots.

It may take some doing but keep poking that hole until something comes out! (you've all got dirty minds )

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