Brown sludge from swirl tank

[rtg]

A quick drive out today ended with steam from the bonnet - pop the lid and there's brown gunk bubbling from the swirl pot cap. The dipstick oil is clear with no emulsion. The engine's got 100k, still drives OK with good oil pressure, no oil leaks and temperature is fairly stable (after replacing water in the swirl tank).

Being optimistic, I'm thinking that it's corrosion from the engine that I did not manage to flush out when I refitted it after sorting out the chassis this year. Otherwise, it could be oil in the water, and I guess that means an engine rebuild, replace etc.. which is not something I have done before.

Has anyone seen this before? If it is a rebuild, is this difficult/expensive or do I simply drop a replacement engine in?

Also - I can't find anyone who does a swirl tank lid (with pressure release) - ideas?

Cheers, Richard.

[davemac250]

Sounds like your system had an airlock and has just cleared it is the oil cap is clear.

Pretty sure you'll find the pressure release valve is the same across the range and from a Golf mk 1.

[v8s4me]

The brown gunk is probably just corrosion and old antifreeze. Sounds like you need to give the whole system a good flush through to the point where the colour of the water coming out is the same as that going in, and then top up with new antifreeze. The perfect job for a winter's day

[rtg]

Thanks for the advice! when I had the engine out I did do a hosepipe flush, but I guess this did not clean all the passageways.

What's the best way to do this? Chemicals or high pressure water?

[davemac250]

Either really.

But I've always used water and then put in premix.

[v8s4me]

Depends how much you want to play about really. You could use these fitting from a plumbers merchant.



I made up this "kit" to pressure test a radiator....



...but if you swapped the airline fitting for a garden hose fitting you could use it to flush out your whole system using your hose. Remove the thermostat first, pull off the top hose and attach the inlet to the to the hose and turn on the water on full. When it runs out of the top of the rad nice and clean, reverse the process by pumping the water in through the top of the rad so it flows out from the top hose. Doing it this way means you should avoid pumping crap from the rad into the engine.

You might want to just flush the rad first anyway as this is the most likley place where the crud has built up.

[rtg]

Many thanks - I've actually got a new rad so must be coming from the heater matrix. Good idea clamping the hose to pipe, will try to make a version here.

[v8s4me]

rtg said:

... I've actually got a new rad so must be coming from the heater matrix....

Which might now have a layer of crud in the bottom? Sounds like you need to do a thorough top-to-bottom flush.