W202 - strange cooling problem

[s class]

Just 4 months ago I did a cylinder head job on my wife's W202 (Link), so I was rather concerned when she phoned me on Saturday evening from about 30km from home to say the car was overheating and she was stuck.  I drove out there, and checked basics like water level, etc, and eventually decided to try and drive home.  The car was at 80 deg when I started out, but very quickly got to 105 deg.  I stopped a few times on the way home to wait for things to cool.  Most of the trip was on the freeway, and I managed to do it at about 80km/h with the cabin heater on full blast, and generally running at 100 to 105 deg.

When I got home, I pulled out the thermostat.  I boiled it on the stove, and found it only just started to open with the water boiling vigorously.  I was lucky to get a chinese knock-off part at the spares shop on Sunday morning (this is a complex thermostat as a one-piece assembly with the housing).  I got home, fitted it, and also checked that the water pump was flowing properly.   The test drive quickly resulted in the same problem - temp up to 105 deg, and wanting to keep climbing.  I limped home, and starting to suspect the radiator, I removed the fan shroud so I could access the radiator.  Most of it was cold - just the top 20% was too hot to touch.  I removed the radiator, and found it was almost completely blocked with calcium type build up.

This is a new radiator (geniune MB) that I fitted when I did the cylinder head.  The car has been running the correct MB coolant mix, but only with tap water - same tap I use on all my other cars without problems.  The engine block is cast iron, head is aluminium, and radiator is copper core - just like all the W116's. 

How can this happen?  And how can the scale have built up so fast?  The car's only done 4000km since the radiator was fitted?

[TJ 450]

That's astonishing and I can only imagine that the deposits came from the water, or some alloy dissolving, hopefully not the latter.

If we used tap water here in Perth, calcium deposits would form very quickly... the tap water is loaded with minerals here. Is that the case in your area of RSA?

As an example, a few months of tap water use in an iron (the type for ironing clothes. ) will see scale crumbling off the thing and all the holes totally clogged with lime deposits.

Tim

[s class]

I'm going to send the radiator in to ultrasonics, and I'll see what they have to say about the stuff inside. 

[TJ 450]

That sounds like a good plan. Then at least you'll know what it is and where it came from.

Tim

[Big_Richard]

its better to be safe than sorry, and never use scheme water in a cooling system full stop.

Distilled water only for me, I always have gallons of the highest quality drinkable stuff lying around the house as it's used in my personal water cooler/boiler.

Could it be that the crap thats clogged the radiator was simply disturbed in the block while the head was removed. I remember seeing some pretty feral things hiding in engine blocks with their heads missing

[WGB]

I had this problem with a 126 300SE 20 years ago and never received a complete answer from Diesel Motors after they finally fixed it.

Mercedes Enthusiast magazine has in the past made reference to a silting problem which was apparently caused by the older amber coloured M-B coolant and this was finally apparently finally solved by the switch to the later Blue Coolant.

I can only assume that the sediment has come from using incorrect coolant or else it was already present and a change of coolant "Liberated" it.

Those of us who have restored really old cars usually put a filter in the upper radiator hose (hoses on an old Ford V8)  and clean it often.

Bill

[koan]

Those of us who have restored really old cars usually put a filter in the upper radiator hose (hoses on an old Ford V8)  and clean it often.

I use the foot off of (one of my) old nylon stockings and position that in the top radiator hose before using any flushing mixtures. I catches all the freed up crap before it blocks the radiator core.

koan

[WGB]

I use the foot off of (one of my) old nylon stockings

koan

Who else besides me would  like to see a photo of Koan in his nylon stocking 

Sounds like a good idea though to use one of my wife's old stockings.

Bill

[s class]

I tried the stocking trick on my blue 6.9 when I first got it, but the stocking blocked up in only about 10km...

Yes, I have seen the error of my ways, and will be buying some drums of distilled water. 

When I had the head off, I though the passages in the engine block were very clean.  Of course, I don't know what was in the heater core and other parts of the system. 

I only dropped off the radiator today at ultrasonics - its the first chance I've had this week. 

[Big_Richard]

i'd think also that stockings will not have a fine enough mesh pattern to filter out ultra fine silt particulate, but i guess its still a hell of a lot better than nothing.

Would be nice to have some kind of cartridge filter in the cooling system, with a bypass system incorperated if it ever becomes blocked

But then, In an ideal world youd design a cooling system that used a thin synthetic oil rather than water and forget about corrosion forever.

[koan]

I tried the stocking trick on my blue 6.9 when I first got it, but the stocking blocked up in only about 10km...

Is that because you pulled the stocking tight over the radiator inlet and put the hose on that?

My method is to feed about 30 to 40 cm into the radiator, fold it back over the inlet and clamp the hose over it. That way there is much larger filtering surface.

Yes, I have seen the error of my ways, and will be buying some drums of distilled water. 

I assume it will be distilled water and coolant because distilled water on its own is worse than tap water, it leaches out ions from the metals in the engine. Tap water around here is pretty good fortunately.

i'd think also that stockings will not have a fine enough mesh pattern to filter out ultra fine silt particulate, but i guess its still a hell of a lot better than nothing.

The fine stuff will flush out, the stocking is only in there temporarily to catch  the chunks of rust from inside the block that would otherwise jam in the radiator.

koan

[s class]

I tried the stocking trick on my blue 6.9 when I first got it, but the stocking blocked up in only about 10km...

Is that because you pulled the stocking tight over the radiator inlet and put the hose on that?

My method is to feed about 30 to 40 cm into the radiator, fold it back over the inlet and clamp the hose over it. That way there is much larger filtering surface.

ah yes, I probably allowed only about 5 to 7 cm of slack.  I had no idea you stuffed so much in.  But it makes sense. 

Yes, I have seen the error of my ways, and will be buying some drums of distilled water. 

I assume it will be distilled water and coolant because distilled water on its own is worse than tap water, it leaches out ions from the metals in the engine. Tap water around here is pretty good fortunately.

Yes, my plan was distilled water plus MB coolant.  Would that be OK?  What does MB recommend in this regard?

[koan]

Yes, my plan was distilled water plus MB coolant.  Would that be OK?  What does MB recommend in this regard?

Only thing I've seen in the M-B literature is to use "potable" water which I assume means is water that is OK for humans to drink.

koan