Coolant leak..

[rwdkev]

Originally Posted by aardvarkash10

......Radiator end tanks

Don't forget the radiator core itself and the joints between the core and those end tanks

[mjk164]

Connor, I would check the radiator filler tank cap...it should be a green one. Earlier ones were a problem and after a while, were not able to hold the pressure and water leaked out with little evidence through the overflow. Buy a new one (not used but good!) for a few pence and try that first. My 1993 960 had the same issue as yours and fixed with a replacement filler cap.

[mjk164]

Connor, the duff radiator caps are grey. These grey ones tend to get little hairline cracks in the threaded portion and leak either out the cap or from the overflow tube.

[2V8s]

interesting, my 1991 960 24v 3 litre also looses a little coolant, although probably only needs topping up once a year and / or every 2-3000 miles.

How could the coolant get into the automatic gearbox? that would worry me a little.

otherwise I was thinking to stick a bottle of K-seal in, as I had otherwise suspected a slight leak from the heater matrix as every so often its quite misted up inside.

[Casheye]

Originally Posted by 2V8s

interesting, my 1991 960 24v 3 litre also looses a little coolant, although probably only needs topping up once a year and / or every 2-3000 miles.

How could the coolant get into the automatic gearbox? that would worry me a little.

otherwise I was thinking to stick a bottle of K-seal in, as I had otherwise suspected a slight leak from the heater matrix as every so often its quite misted up inside.

That doesn't sound too unreasonable.

As the radiator is split and shared, cooling the engine and gearbox, there's the potential for splits and cracks. Maybe after extremely low temps and only having water in the rad, it freezes and cracks or just weakens the core enough that the heat expansion after when the engine is running creates a gap for the coolant and ATF to mix.

[Laird Scooby]

Originally Posted by 2V8s

interesting, my 1991 960 24v 3 litre also looses a little coolant, although probably only needs topping up once a year and / or every 2-3000 miles.

How could the coolant get into the automatic gearbox? that would worry me a little.

otherwise I was thinking to stick a bottle of K-seal in, as I had otherwise suspected a slight leak from the heater matrix as every so often its quite misted up inside.

There are oil to water heat exchangers built into the end caps of the radiator on an auto, the ATF passes through these and is cooled by the surrounding coolant, hence the pipes running to the radiator from an auto box.

If coolant changes are neglected so the corrosion inhibitors in the antifreeze are no longer working, the oil tanks within the end caps can leak. Thing is, because the ATF is being cooled in the return line, it's under very little pressure - unlike the cooling system which is pressurised so coolant could be forced into the gearbox.

To give an idea what i mean about the heat exchanger, this is a diagram of a Jeep Cherokee automatic radiator with one oil to water heat exchanger in the bottom of the radiator. It illustrates the idea though :



As you can see, if the oil part corrodes and splits it will allow coolant in.

I'm planning a separate ATF cooler for mine, mounted in front of the normal radiator a bit like an A/C condensor to elimintae the risk of coolant getting into my box.

If yours needs topping up once a year then there is either a very slight leak that you won't find until it gets much worse or the cap needs renewing.

[2V8s]

ok thanks that makes sense.

I will change the cap and also do a fluids change. Must admit last time the coolant was changed probably was a few years ago, but its got plenty of coolant mix in it.

see how it goes with a new cap and if that doesn't stop the slow leak I will add some k-seal.

thanks

[ericbeaumont]

Some swear by K-Seal, but if your system has had that and a few others - Radweld and so on - added by previous owners, beware, as the accumulation can clog smaller pipes - turbo water pipes come to mind - and cause new problems. Steel Seal is supposed to be good as it contains no sediments, but by the time I thought it might be worth a try, any number of cloggings had been found and the whole pipe system had to be stripped and cleaned.

If you have the patience, better to find the leak and deal with the real cause.