Removal of 6.9 Water Pumps

[Styria]

With the advent of the extremely hot weather some sections of Australia, including Sydney, have experienced, failure of water pumps, particularly 6.9's, have become an issue.

There has been confusion from time to time regarding the amount of work involved in order to remove the pump. Some have maintained that the crankshaft damper requires removal, others have suggested that it would be best to also remove the water pump housing that separates the pump from the engine block.

There is absolutely no doubt that it is NOT necessary to remove the damper. Whilst the impeller is ALMOST an interference fit in the housing, the pump can be removed.

Regarding the removal of the housing itself, I don't particularly like removing those on account of two reasons.
1) The lower flange bolt on the off side can be rusted in and it is quite easy to damage the Allen headed bolt, and

2)There is a spacing washer between the engine block and the Air Conditioning bracket. That spacer can be quite awkward to replace, but it has to be in place to stop coolant leakage from that particular retaining bolt. In addition, I prefer to see a hex bolt in its place. Regards Styria

 

[s class]

That spacer washer is an interesting bugger. I found the original one missing on my blue car when I removed the A/C bracket - some previous person had substituted something 'almost right'. Took me some time to get it all correct again.

 

[Styria]

Yes S-Class, it's one of those jobs that's "almost too hard". I speak from experience - it's just so easy to lose that spacing washer, and once it falls down into the cavity between the engine block and A/C bracket cavity, you just don't get it out again, let alone find it. Thus, I always have a spare unit on hand. I also stuff some form of rag just inside the cavity to stop the washer from falling all the way down. Regards Styria

 

[TJ 450]

The water pump off my 6.9 was able to be removed with the damper in place.
It was a very tight fit and required some manouvering to allow it past the harmonic balancer. If the pump has not been removed before, as it hadn't in my case, one should be prepared for at least one bolt to shear off.

When undoing the socket head screws, it is also imperative that the hex socket fits without any play. If one decides to replace the bolts(recommended), you are best sourcing equivalents from aftermarket sources.
The bolts you get from M-B now are not the same as the originals.
Some anti-sieze compound works wonders.

I will be using M-B blue coolant when I reassemble my vehicle.

Tim

 

[Styria]

Hi TJ450, my post regarding the removal of the 6.9 pumps was purely in response to what I had seen written elsewhere by various sources - be that US or otherwise based.

It was easy for me to be decisive in stating that the crankshaft damper does not have to be removed -yet, I know for a fact that a Mercedes Specialist repair shop found it necessary to remove the damper contrary to advice they had sought and I had given.

I know it is a tight and interference fit, but that refers primarily to the water pump impeller. One just needs to be very, very careful when breaking old sealant that's been there probably for years. That's the tricky part - to just loosen it. The rest is comparatively easy. So, don't remove the damper. I find it also easier to remove a couple of other items that prevent easier access to the job in hand. Most of us try and get by without removing 'this or that', yet if we did, many a job would be that much easier.

If you decide to use the MB 'Blue' coolant, just bear in mind that it is a really 'searching' product - it cleared out all the nooks and crannies on Gleaming Beauty, and whilst it was a case of a valve grind and de-coke 'not too far away', it certainly accelerated the need for that job. Regards Styria