KTM 450 - 530 Water Pump Seal Replacement

As documented by


Difficulty Beginner

Expected Time 1 hour

March 2nd 2011

Originally published on

KTM 450 - 530 Water Pump Seal Replacement

A common problem with the 450-530 KTM's is a leaking/weeping water pump seal. You look down and notice a drip or wet trail coming from the weep hole on the water pump cover and know it's time to change the seal. The water pump seal is installed backwards at the factory and will eventually leak, some take longer than others to do it. My last 530's water pump seal started weeping at around 80 hrs, my current 530 just started leaking at 51 hrs.

I've had a few people email me asking questions about changing the seal out so I thought I'd take some pictures this time around.

Tools You Will Need

  • Torque wrench in in/lbs
  • 8mm socket
  • 10mm socket

Parts You Will Need

KTM Part NoDescriptionNotes
0760102440 Water Pump Seal (outer) The KTM parts diagram shows the wrong
number for the outer seal; don't order that
number or you will get a inner seal, order
the part number listed here instead!
78035053000 Water Pump Cover Gasket  

Handy Torque Values

Nut, Water Pump Wheel 4.43 ft/lbs (6nm) Apply Loctite 648
Screw, Water Pump Cover 7.38 ft/lbs (10nm)  

Start by draining the coolant, remove the coolant drain bolt (Red Arrow) and place a suitable catch pan under the engine (I like to use a long funnel to direct the coolant into the pan). Note: When you pull the bolt a small bit of coolant will drain then it will stop, you then have to open the radiator cap to let air into the system so that it will continue to drain. Open the cap slow, otherwise you will get coolant everywhere.

Keep track of the copper sealing washer on the drain bolt so it doesn't get lost, also make sure it's installed upon re-assembly. After the coolant is drained remove the remaining three water pump cover bolts (Blue Arrows).

Loosen the clamp on the water pump cover hose connection and remove the cover from the bike. If your careful removing the cover the gasket will usually come off in one piece and can be reused...that being said I usually like to change gaskets with a new one when removing/installing covers.

This picture shows the different length bolts for the water pump cover and their position. Take note of which bolts go where so you can get them back in the correct location.

Remove the water pump impeller nut (Blue Arrow).

Carefully pry the water pump impeller off the shaft, go slow so you don't damage the impeller. Here I'm using two small screw drivers to wiggle the impeller off the shaft.

Water pump shaft with the impeller removed.

And here's the problem with the stock pump seal. A spring loaded lip seal should always be installed with the spring twords the pressure, this way the pressure pushes with the spring and helps make a good seal on the shaft. The stock seal (Red Arrow) is installed with the spring facing the weep hole (inward), allowing the coolant pressure to fight against the spring and leak if everything isn't perfect (spec of dirt that entered through the weep hole etc).

Keep track of the spacing washer (Blue Arrow) that's located behind the water pump impeller. Make sure this gets installed behind the impeller during re-assembly or your impeller will bottom out and bind with the case.

There are a couple methods to remove the outer water pump seal. You can blow compressed air in the weep hole and use the pressure to push the outer pump seal out, this method can take high pressure to make it work and several tries. You'll also be forcing air through the inner pump seal and you'll hear it venting out the transmission vent hose.

If you don't have access to compressed air or you don't have luck with the compressed air method you can use a drill and a screw to remove the seal. Place a small dab of grease on the tip of a small drill bit and drill a hole through the outer water pump seal. (The grease will collect the small metal shavings and keep them from getting on the inner seal). Keep light pressure on the bit so when it pops through it doesn't damage the inner seal.

Once the hole is drilled insert a small screw into the hole.

Grab the screw with a pair of pliers and pull on the seal, it will pop right out. The white stuff between the two seals is factory grease.

Here's a close up of the inner seal. This seal is usually in great cond and you shouldn't need to change it out. If you do need to remove it you can use the same greased drill bit technique to remove the inner seal as well, be very careful when drilling through the inner seal not to let the drill bit pass through the seal and damage the bearing that sits right behind it, keep light pressure on the bit when drilling.

The red arrows show the three stand offs that are molded in to the inner seal, when the outer seal is pressed up tight against them it leaves a small space between the two seals. If the outer seal starts leaking coolant will pass into this space and drain out the weep hole (Blue Arrow) preventing it from possibly reaching the transmission and letting you notice it so you can change the seal.

Here's the new seal, you will want to install it opposite of the original installation and the shop manual. As mentioned above the pressure in the coolant system will push on the spring (Blue Arrow) and help it retain a tight seal on the impeller shaft.

Add a small dab of grease on the inner lip of the new seal, slide the new seal onto the shaft and use a socket the matches the outer edge of the seal to push it up against the inner seal.

New seal in place.

Install the spacing washer on the shaft.

Install the Impeller on the shaft and the water pump nut, torque the nut to the proper spec. Since I have the pump apart I decided to install the KTM Hard Parts High Flow Water Pump Kit.

Re-install the pump cover and torque the bolts to the proper spec. (The orange spacer pictured is part of the high flow kit and ads extra clearance for the taller impeller).

Refill the coolant and that's it, enjoy your leak free ride!