Water pump Overhaul & System Flush


It's not my intention in this article to do a step_ by_step How-To of the LC8 (950/990) water pump overhaul. Pyndon already did an excellent How-To with a huge amount of detail elsewhere in the HOW in his article titled "Water Pump R&R." My intention here is to chronicle the specifics to my 2003 950's water pump and point out a few things I found worthy of comment for the "Collective" awareness, including the "proper" way to flush the cooling system.

In the image below are the parts and a couple of special tools that I used for this service. All of the parts inside the gasket, including the gasket, comes in a kit from KTMTwins in San Francisco, CA, USA. for $85 USD as of this writing.

In the upper right is a thermostat 60035017000 $29 USD Cheap Cycle Parts which I replaced as preventative maintenance (PM). The radiator cap 58035016000 $19 USD Cheap Cycle Parts in the lower left is something I replace every time I change the coolant as a PM. Faulty and/or dirty radiator caps have caused overheating problems in the past on a number of LC8 engines, and may have also caused the replacement of functioning water pump seals and/or head gaskets due to misdiagnoses.

The two tools on the left are the holder for the impeller 60029082000 $27 USD from Cheap Cycle arts and right above it, the seal mounting tool 58529005000 $22 USD from Cheap Cycle Parts

The parts are routinely being upgraded by KTM, so be sure you use the latest parts for the best results. Also, Craig Johnson of CJDesigns has developed an impeller shaft with a very hard coating that looks to last much, much longer than current OEM designs. I will be upgrading to one of Craig's shafts on my next rebuild.

I use Engine Ice coolant. Maybe that has something to do with seal longevity (or not), but it definitely allows my bike to run cooler (ie: the fan comes on less easily/often). You'll need two 1.9 liter bottles at ~$20 USD the first time you use it, as the 950/990's hold 2.1 liters.

To make sure you also clean the radiator and its hoses, I suggest draining the coolant and filling the system with a solution of 50% water and 50% white vinegar before disassembly and run through one heat cycle, then drain at the bottom radiator hose. Fill again, but this time with 100% water and run for another heat cycle, and drain again.
Caution: dispose of used coolant properly. It is poisonous to humans and animals

Now, lets get started

First a shot of the front header pipe and it's cylinder head mount. The front header pipe must be removed to remove the inner clutch cover along with the water pump internals. Don't be surprised if the studs unthread from the head, as the lock nuts KTM uses (14mm w.s.) in this application are tighter than the studs.

A couple of these magnetic parts trays come in very handy when doing projects such as this. I have one for the chassis fittings and another for the engine.

Once the pump cover is removed, the plastic impeller can be inspected for damage. Look for any contact between vanes and the inside of the pump cover. A few early bikes had problems with dislodged or missing circlips that allowed the impeller to move in and out of the bearings. The result was plastic bits showing up in the coolant recovery tank, and eventually, overheating. This engine does not show signs of contact. The circlips were all present and functional.

The impeller is a very tight fit on the shaft and some care must be taken to remove it. I had a new impeller in my kit, so I just pulled it off with pliers. I advise having a new impeller on hand when you do this overhaul.

Once the impeller is removed, you can really see the extent of the leftover casting sand that permeates the 950's cooling passages. One theory as to why the water pump seals on some of these engines fail so quickly is that this leftover casting sand gets between the seal and the shaft and wears it out (more on this later). I flushed this engine's cooling system early in its life, and as you can see, there is still some sand present.

If you're just flushing the cooling system and don't need to R&R the pump shaft and bearings, you can skip the next few steps and go directly to flushing. Also, if you're just replacing the seal (as dictated in the Maintenance Schedule for the 950 Adventure every 15000 km) you can do so at this point without further disassembly.

You can see the bolts (18) that must be removed to pull off the inner clutch cover. Note: Only one of the outer cover bolts need be removed (green arrow). Also, don't overlook the one inside the pump itself (yellow arrow).

A little friendly persuasion may be necessary to get the cover to release. Be gentle.

This is an image of one of the areas in the inner cover water passages that collects casting sand. There is a small amount visible here. I have seen much worse. Clean all of these areas and the rest of the pump chamber thoroughly. It should be "squeaky" clean, if you expect long life out of your new seal and shaft.

Here's how the seal installation tool works. Lube the seal and tool with lots of your favorite seal lube. No matter what method of protection you use, it's VERY important that the seal is not damaged by the very sharp edges of the new shaft. I've seen several seal failures as a result of folks not getting this step right. I also spray some silicone mold release agent (available at most good hardware stores) on the edges of the seal and the cover where they mate. This allows the seal to be removed easily next time (Especially helpful if you're doing a seal only replacement).

The seal is then pressed into its recess with a seal installation tool and hydraulic press (or a proper size socket and hammer, if need be). Just take great care that it goes in evenly or you'll make a mess of it and the seal will leak straight off. Slow and careful here. This is where most jobs are botched.

Be very careful that the new gasket doesn't become misaligned when you install the cover. Also, make sure that the cover is fully seated and flush with the engine case all around before tightening any of the bolts. At least one owner has broken the cover by not following this rule. For the clutch cover to seat fully, you will need to turn the pump shaft by hand to engage the balancer shaft in the engine.

This is the "proper" tool for the impeller installation. Other methods may work OK, but why skimp on such an important piece on your $15,000 bike. The bolt gets Blue Locktite and 10 NM of torque. The tool keeps that torque from being applied to the slot in the shaft. Remember, it is so hard that it verges on the edge of brittle. You DO NOT want to break the shaft after all of this work (or worse, have a cracked shaft break on the trail miles from nowhere), now do you?

Before installing the pump cover, insert the cover bolts to block off any passages that go into the crankcase, and do a proper flushing of the coolant passages in the engine (as shown in the image below). The casting sand is located in the cylinders and heads and needs to be attacked directly with water pressure, as close to the source as possible. This is why I prefer the direct method of a hose directly into the water passages, rather than trying to get the water pump to remove it all though the radiator. As you can see from the above photos, much of the sand tends to collect in nooks and crannies of the inner cover and surfaces behind the impeller, so these items must be removed and thoroughly scrubbed for all sand to be effectively removed.

I have used gun cleaning brushes (the nylon bristle kind on thin flexible shafts) to get deep into the engine passages. Also remove the overflow container and clean it thoroughly. A mixture of crushed ice and baking soda works well for this chore. Remember "squeaky" clean.

Clean the cap if not replacing it, paying particular attention to the area under the disk at the center of cap (inside). This is the one-way valve that allows hot coolant that was pushed out of the cooling system, past the pressure relief valve, and into the reservoir during operation, to return to the engine and radiator when cool. If this valve doesn't seal, coolant will be forced out into the reservoir at the wrong time causing it to overflow onto your right foot and the ground. This has been misdiagnosed as a blown head gasket by some. I prefer to install a new cap each time I change coolant.

Now, button everything back up, install Engine Ice (or your favorite high quality silicate free brand) and "burp" the cooling system.

As for "burping" here's a great tip by BobbyC that I tried and it works great. Saves a lot of fiddling (especially when you're by yourself).

"I bled the system from the upper bleed screw at the water pump. Then I squeezed the 1" diameter hose on the left side going into the radiator until most of the air was pushed out. You might have to squeeze this hose 10+ times. Fill some more and close the radiator cap. Fill the reservoir to the max line and start the bike. Run it until the fan comes on and bleed from the bleed screw on top of the radiator. There should be very little air from this. I thought there was still some air in the system so I went for a slow ride around town. When I got back, there was a 1/4 of the coolant in the reservoir tank that was sucked back into the system. I topped it off and kept an eye on it for the next few rides."

Here is an image of the old shaft. You can see the two grooves worn into the surface by the double lip seal. The left is the impeller end and has the pressure and heat of the coolant. The right side is the engine crankcase end and two bearings and their seals protecting it from the hot engine oil. There shouldn't be any pressure on this side if your crankcase ventilator is functioning properly (and you don't have combustion blow by from improperly seated rings).

Here's a close-up of the groove area from the photo above. The groove on the left is considerably deeper than the right. You can also see a wide band of wear just to the left of the left side groove. I suspect that is caused by leftover casting sand in the coolant passages that migrated to the seal area. This engine exhibited NO signs of coolant leaking into the oil at the time of this pump overhaul at 19,733 miles. I suspect it wouldn't have gone many more miles before the seal gave out.

The newest shaft has a harder surface than the one that came in my 2003 bike. The seal is also a different material (Teflon) that should handle the heat better and be easier on the shaft than the old parts. This seal and shaft were first installed at the factory in production LC-8's built after July 2007, so it will be awhile before we get much of a data base to draw any conclusions about longevity. The pundit's suggest that 32k km (20k) miles should be the mileage at which the pump is overhauled. I suspect they are erring on the side of caution (I would suggest 80k km (50k) after a proper system flush), but their recommendation allows for other variables, such as more casting sand in the system.

An interesting note is that the Service Manual (since REV 1-2006) has dictated the replacement of the water pump seal every 15000 km (9300 mi) as part of the Preventative Maintenance Schedule. This is not in any other LC8 PM Schedule, making it look more and more like the seal problem was isolated to the 950 Adventure production line. Since the entire LC8 line used the same seal and shaft until July 2007, it begs the question: Was something wrong with the 950 Adventure QC in particular?

There are KTM LC8's with close to, and many more miles than, mine without water pump failures. There are also many bikes with much less miles than mine with seal failures. I suspect that there is more than the design or even the materials of the parts in the pump at play here. Some have been improperly installed parts. I have seen a few of those. Also, many folks have changed the seal and shaft when they were still good out of fear, caution, or the result of other problems that caused overheating. But, it's looking more and more like leftover casting sand from the manufacturing process could be the common denominator here. KTM even directs its service personnel in Tech Bulletin 0544 (April 15, 2005) to flush the cooling system of 950 Adventures at the first service to remove "Sand deposits from the casting process." I flushed my bike's cooling system early in its life, which may have resulted in its seal lasting so long. Also, there may be more, or less sand leftover in different engines resulting in earlier failures in some and longevity in others.

Until someone finds something else that can explain such a wide range of seal service lives, I will continue to recommend a thorough flush of all 950 Adventures early on and installation of the latest seal and shaft as needed. It may not be a bad idea to do this with all LC8's (couldn't hurt).

Note: I have no affiliation with any of the vendors, manufacturers, suppliers, or other companies mentioned in this article. They are simply solutions that have worked for me.

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