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MG MGF Technical - Flushing coolant

Hi
What is the best way to flush out the old antifreeze on my mgf before fitting
A new radiator,I have the old yellow/green coolant in and need to change
To OAT type.
Peter
p le rossignol

Best way to get it all out is to evacuate it
William Revit

Silly me I never thought of that.
p le rossignol

Not silly at all Peter
A lot of people don't realise that the cooling system can be drained, then sucked to a vac. using a simple evacuation fitting on a airhose,which removes all remaining coolant, then refilled using the same valve fitting
I reckon Harbor freight would have a kit, you don't need an expensive one, they all work the same
willy
William Revit

Thanks for explaining that Willy i did not know about
that.
Peter
p le rossignol

https://www.youtube.com/watch?v=_WCRcuCZI50
William Revit

I would use that system at least two or three times, twice with cleaning or flush before the refill as I'd want as much muck, crud and bits of old coolant out as possible. If you look on the midget and Sprite and MGB Technical Archives you can see photos of large lumps of jelly like stuff found to be clogging the system where dissimilar (and/or old?) coolants have mismatched.

On a standard, drain of coolant or oils, especially if done cold and as quick as possible, most owners don't realise how much old existing fluid and muck and crud they leave in as residue which means the new fresh fluid and its effects are diluted by the residue left in.

If they compared dry capacity refill quantity to the amount of fresh fluid they were able to get in they'd know how much residue they'd left in. Of course unless the components were fully taken apart and cleaned there's always going to be some residue at normal drain downs, even those done with the fluids all warm or hot and left to drain for long periods, but the more old fluid and muck/crud you can get out at each drain (and clean/flush) the better.
Nigel Atkins

Willy,Nigel

Thanks for your comments much appreciated.

Peter
p le rossignol

Normally Nigel, I'd 100% agree with you, and good advice ,but Peter is replacing the radiator, and on a MGF letting them bottom hoses go drains almost everything, he could pull a heater hose off the engine and poke the garden hose in to flush out the heater and back the other way to flush the block while the rad. hoses are off, just to make sure but there won't be much in there-
I take it that it's an early car, has it had the thermostat/bypass mod. done--? well worth doing
willy
William Revit

Willy,
the very basic garden hose flush/back-flush/flush on the matrix, engine, rad and hoses is my simple way of doing things (only on a warm day with toilet nearby) and then a very cheap plastic syphon.

But I was thinking for Peter's MGF of just using the machine to do the work. Perhaps a clean and flush with old rad still fitted, then take the rad out and fit new rad, top up system with flush water and final evac refill of correct coolant.
Nigel Atkins

Actually if it was my car I'd do the normal drain, refill with cleaner and the run engine with cleaner in and then do the flushing and refill cycles.

I'd want to know everything internally is as clean as possible so in future I'd only have to do the routine (warm/hot) coolant/antifreeze drain and refill changes.
Nigel Atkins

HI Guys
Great discussion here.ive had the MG 10 years now
its going well stainless steel pipes were fitted when i bought it,no coolant change since then.the radiator
is rusty along the bottom with a slight weeping of coolant,not needing to top up yet Living in Jersey you
cant go far in an Island 5 miles by 9 speed limit 30
MPH most roads.Do i change it now or wait till it gets bad.
Peter
p le rossignol

Peter,
it's your car only you can decide what's worth doing to it in your use and opinion. Seems the yellow/green was thought to be more corrosive (but the 10 years it's been in might disprove that). A leak like yours won't mend itself, a load of crud and muck might block it off for a while though.

In the old days you'd put something like Barrs Stop Leak in the rad in liquid or solid (dog's turd) form. The AA use(d?) K-Seal (don't ask how I know). Some view the use of such products as restricting waterways elsewhere.

What does your Driver's Handbook say about the interval for changing the coolant/antifreeze as 10 years is a very long time and the longlife OAT are 5 years IIRC and the old stuff used to be every 2 years.

They seem now to test that the antifreeze part of the coolant is still in spec but this forgets the additives in the coolant that diminish and those are to help restrict corrosion.

Changing to a different type of coolant will require a good flush out of the system as a minimum, what's the need to change to OAT type?

https://barsleaks.com/product-category/cooling-system/

https://www.kseal.com/uk/products/k-seal?gclid=EAIaIQobChMI5svHi6uq7AIVSrTtCh33LQ4WEAAYASAAEgLo7_D_BwE

Nigel Atkins

Nigel
you cant get the coolant that i have anymore
unipart super plus 3 so i have to go OAT.
Peter
p le rossignol

Fair enough Peter, probably not been able to get it for years then.

Sounds like it might have been some "special" coolant that MG specified, I won't guess or speculate on the reasons for them specifying it but like with oils better products are available now.

You will need to give a good clean and flush which might remove some crud and muck that causes the rad to leak more, or it might not.

Giving the whole system a thorough clean and flushes could possibly improve the efficiency of the heating/cooling system enough that you may not need (want?) a new rad.

If the existing rad leak increases after thorough system and rad cleaning and flushes then you can consider whether to replace it with a new rad or put a sealer in. K-Seal has - "sealing holes up to 0.635mm in diameter - sealing slots or crack up to 0.254mm wide by 12.7mm long".
https://www.kseal.com/uk/expert-advice/engine-problems/radiator
Nigel Atkins

This thread was discussed between 04/10/2020 and 10/10/2020

MG MGF Technical index

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