15 replies to this topic

[george_hill]

Hi all

1985 998

I have just changed my coolant, I added 1.5l of concentrate but it only took another 0.5l of water to fill it back up. Is this normal because the hains manual says it's 3.6l capacity. I ran the engine up to operating temperature when I did this but it still didn't go down very much


Thanks
George

[cal844]

3.5 is total capacity of a dry engine and heater matrix. Ideally you'd want to use some CLR(and run it for a week) or just flush it thoroughly until clear.

[mullet]

I have the same question.  1984 Mayfair, automatic, 1000cc.  Flushed and cleaned (<Liqui Moli) the system entirely (so I thought).  This included taking the heater out which, so I read, may be in an even lower position than the bottom hose of the radiator...but probably not since the to/from hoses are higher than the bottom radiator hose.

 

But it only took about 2.4 litres of coolant to refill it.  After driving it, I presumed any trapped air will be dislodged.  Level of coolant still the same after driving.  So where is this extra 1.1 litres hiding?  Or perhaps it is perfectly normal for 1.1 litres to reside in the engine after flushing (but then, is the coolant very diluted)?

 

Nothing lumpy was seen in the flushing; just very red water and thicker towards the end of the first flush.

 

I have an overheating issue.  I'll replace the pump this week, which is currently the likely culprit.  Just wondering if this mysterious 1.1 litres might indicate something more serious, like a blockage or resting sediment and contributing to further heating inefficiencies? 

Edited by mullet, 08 June 2025 - 03:01 PM.

[imack]

Removing the pump will partially drain the block to the level of the bottom of the pump. To remove the rest of the coolant you need to remove the drain plug from the rear of the block. All A series blocks had this drain plug, but,I think only early A+ blocks had it. But, even if your block has it you may find that even with the plug removed the drain is still blocked by debris and rust. It can often be cleared with a stiff piece of wire or a drill bit.

[imack]

A series and early A+ drain plugs

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[mullet]

A series and early A+ drain plugs

Thanks Imack.  I just went out to have a look, and it doesn't seem the engine has the same design.  I cannot find any nut sitting vertically as per your photo.  I had read some mini's don't have a drain plug at the bottom of the radiator, nor a drain plug in the engine.  Whether the case of not, I don't know.  Perhaps an 1984 Mayfair relies on the bottom hose as the drain alone (no radiator drain plug exists for me)?  So do you think removing the pump to replace will give access to the ALMOST lowest point, to that 1.1 litres?  And I understand with some careful prodding and scraping via the pump area, I might tell if there may be a blockage or sludge/debris?  Some flushing at the low point too I guess is wise.  I can jack the car to tilt.

[Spider]

I am somewhat sure in 1984 the blocks still had a drain plug on the back of the engine block. They can be hard to see, it'll be just below the tappet cover, the engine steady bar can obscure a view of it.

[mullet]

I am somewhat sure in 1984 the blocks still had a drain plug on the back of the engine block. They can be hard to see, it'll be just below the tappet cover, the engine steady bar can obscure a view of it.

Hi Spider.  I am going to take another, more thorough, look shortly today.  Like the oil drain plug, I assume this is the lowest point of the cooling system?  I wonder if the last 1.1 litres is sitting behind this plug and is so heavy with sludge, that it didn't flush out when flushing via the thermostat opening.  Instead, the almost clean water just ran over the top of it.  If (as expected due to heating issues I am trying to fix) the pump isn't working, then in theory this sludge wasn't drawn up with currents when flushing and cleaning and turning over the engine.  A lot of theory there, but possible? 

 

If I remove the new thermostat for additional flush with this drain plug open, can the new thermostat gasket I just installed be re-used?

[Ethel]

I wouldn't worry too much if it was well flushed until it ran clear. You could lift the car on the  clutch side, but if all that comes out is water...

 

It's a good argument against premix antifreeze though.

[Spider]

Hi Spider.  I am going to take another, more thorough, look shortly today.  Like the oil drain plug, I assume this is the lowest point of the cooling system?  I wonder if the last 1.1 litres is sitting behind this plug and is so heavy with sludge, that it didn't flush out when flushing via the thermostat opening.  Instead, the almost clean water just ran over the top of it.  If (as expected due to heating issues I am trying to fix) the pump isn't working, then in theory this sludge wasn't drawn up with currents when flushing and cleaning and turning over the engine.  A lot of theory there, but possible? 

 

If I remove the new thermostat for additional flush with this drain plug open, can the new thermostat gasket I just installed be re-used?

 

It's not the lowest point, but the furthest point. If the plug hasn't been removed in a while, often the passage behind is gunked up, I clear them using a 1/4" / 6 mm drill bit, just turning it by hand until I get a flow, then back flush through it blasts most of the rest of it away. It might not seem important to clean this but overall, it's small things like this if left that add up to a car that will run hot or over heat.

You'll likely find though, that the residual coolant is being held in the bottom of the radiator.

If the gasket comes away clean, yes, you should be able to re-use it.
 

[mullet]

 

Hi Spider.  I am going to take another, more thorough, look shortly today.  Like the oil drain plug, I assume this is the lowest point of the cooling system?  I wonder if the last 1.1 litres is sitting behind this plug and is so heavy with sludge, that it didn't flush out when flushing via the thermostat opening.  Instead, the almost clean water just ran over the top of it.  If (as expected due to heating issues I am trying to fix) the pump isn't working, then in theory this sludge wasn't drawn up with currents when flushing and cleaning and turning over the engine.  A lot of theory there, but possible? 

 

If I remove the new thermostat for additional flush with this drain plug open, can the new thermostat gasket I just installed be re-used?

 

It's not the lowest point, but the furthest point. If the plug hasn't been removed in a while, often the passage behind is gunked up, I clear them using a 1/4" / 6 mm drill bit, just turning it by hand until I get a flow, then back flush through it blasts most of the rest of it away. It might not seem important to clean this but overall, it's small things like this if left that add up to a car that will run hot or over heat.

You'll likely find though, that the residual coolant is being held in the bottom of the radiator.

If the gasket comes away clean, yes, you should be able to re-use it.
 

 

Thanks Spider!  I keep looking and cannot for the life of me find this drain plug.  Frustratingly, I cannot find any photos of the back of a stripped out engine that matches mine.  The engine I have seems to be this one (at least the form of it front the front appears to match): https://www.minispor...ine-10-3-1.html

Very disappointing if I am unable to drain 100% of everything and no matter how much I google, cannot find information specific for this engine.

[imack]

The picture you have put up is of an A series. If that is what you have got in your car then it will have a drain plug. Post a picture of the distributor/alternator side of your engine and we can tell you if you have a A series or a A+ engine.

[Designer]

The picture you have put up is of an A series.

 

Hi,

 

The heading does say A plus in that picture.

 

Paddy

[mullet]

The picture you have put up is of an A series. If that is what you have got in your car then it will have a drain plug. Post a picture of the distributor/alternator side of your engine and we can tell you if you have a A series or a A+ engine.

Hi Imack & Paddy.  I took a video slowly around the engine:

https://1drv.ms/v/c/...IOM6BA?e=VAmEsr

A+ written on the top, clearly.  Just noticed that....d'oh!  Does this help?  Where might this elusive drain plug be?  I think you can see the sloshing of coolant under the level of where the pump was.  Perhaps the 1.1 litres )

[imack]

The fact that your engine is an A+ means there's a good chance that it doesn't have the coolant drain plug in the block. Unfortunately, only very early A+ blocks retained this feature.