Part 04 Removing the Upper Coolant Plumbing or "Coolant Spider" ...

Introduction ...

This page contains photos of the process of removing the upper coolant plumbing or "coolant spider" components from a ROTAX 912ULS engine (built August 2006).



ROTAX 912ULS Free access to coolant system spider

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With both inlet manifolds and the ignition coil set and SMD's removed we now have access to the coolant spider ...

The coolant reservoir (small black container with the radiator cap on) and the four coolant return pipes connected to it from the top of the cylinder heads are commonly referred to as the coolant spider.

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ROTAX 912ULS coolant elbow hose clips

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Slide the hose clips down the coolant hose away from the coolant elbows attached to the cylinder heads. Do this for all four cylinders. There is a special Rotax tool that makes manipulating these hose clip very easy. Failing that use a pair of pliers. Don't over squeeze them otherwise they won't clamp as hard if you try to re-use them.

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ROTAX 912ULS pulling coolant hose ends off the coolant elbows

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Now carefully wriggle the hose off the coolant elbows being mindful of the fact that the coolant elbows are delicate and can be distorted or bent out of shape if you are too heavy handed or pull too hard on the coolant hose. Gentle heat and a twisting action can help to release coolant hose that has been in place for some years ...

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ROTAX 912ULS pulling coolant hose ends off the coolant elbows

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Here you can see one of the coolant hoses released and just resting on the coolant outlet elbow ...

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ROTAX 912ULS pulling coolant hose ends off the coolant elbows

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Note that the hose that goes to cylinder 3 coolant elbow from the coolant reservoir is a "formed" right angle piece of hose which has it's own Rotax part number. The rest of the coolant hose just comes off a hose reel and is cut to length. This is worth bearing in mind if you are doing a 5 year rubber replacement.

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ROTAX 912ULS disconnecting the coolant reservoir to coolant overflow hose

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Once all the coolant hoses have been removed together with the overflow bottle hose then the coolant spider assembly may be removed.

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ROTAX 912ULS the removed coolant spider on the bench

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The coolant spider on the bench.

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ROTAX 912ULS plan view of engine with the coolant spider removed

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Rotax 912ULS minus the coolant spider. Note the coolant elbows still bolted to the cylinder heads. We can remove these now making a note of which cylinder they come from. You will see they are all set at different angles and generally point roughly towards where the coolant reservoir sets on top of the crankcase.

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ROTAX 912ULS upper coolant elbow o-rings

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The seal is provided by an red / orange o-ring.

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ROTAX 912ULS coolant elbow on the bench

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One upper coolant elbow on the bench.

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ROTAX 912ULS coolant elbow on the bench

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If you examine one closely you will see that it is a two part component. The base plate and the bent tube. These should be bonded together using Loctite 648 (green). You may find that some have been bonded using Loctite 243 which isn't a high temperature compound and is prone to leaking. If you come across one that shows signes of leaking it is best to rebond it with 648. The bent elbow screws in to the base ...

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ROTAX 912ULS removing the lower coolant hoses

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Now is a good time to remove the lower coolant hoses as well.

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ROTAX 912ULS top of the enbine is now clear

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A view of the engine with coolant spider components removed ...

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