Part 37 Re-Assembling the Coolant Spider ...

Introduction ...

This page contains photos of the process of re-assembling the "coolant spider" to a ROTAX 912ULS engine (built August 2006).



ROTAX 912ULS Reassembling the Coolant Spider

Image 1

Here is the existing coolant spider exactly as removed from the engine at disassembly. The customer for this particular 912 rebuild job requested that all rubber components are replaced as per Rotax's 5 Year rubber replacement recommendations. This includes all coolant hoses both upper and lower ...

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ROTAX 912ULS Reassembling the Coolant Spider

Image 2

New coolant hose. The genuine Rotax hose is expensive but it is important to remember that parts of the coolant circuit are in a state of suction. For this reason the coolant hose used must be able to hold it's form under suction at the full range of operational temperatures. What feels solid at 20 degrees Celsius may be considerably "softer" at higher operating temperatures. If due to this softness at higher operating temperatures the hose isn't capable of holding it's shape under suction (and collapses) then it is possible that coolant flow will be either be inhibited, or worse, blocked altogether. Other cheaper coolant hose is available but personally I believe that it is false economy to use any product other than that specified and tested by Rotax ...

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ROTAX 912ULS Reassembling the Coolant Spider

Image 4

Here we can see one slightly tatty coolant reservoir. Note that the rubber plate that protects it from percussive damage should the base of the coolant reservoir come into contact with the upper surface of the crankcase is of the older style. The older style rubber plate offers a smaller surface area of protection to the base of the coolant reservoir. For this reason we are going to replace it with the revised version ...

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ROTAX 912ULS Reassembling the Coolant Spider

Image 5

Note how the rubber plate clips over the inlet and outlet tails ...

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ROTAX 912ULS Reassembling the Coolant Spider

Image 6

A plan view ...

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ROTAX 912ULS Reassembling the Coolant Spider

Image 7

The revised version of the coolant reservoir protection plate ...

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ROTAX 912ULS Reassembling the Coolant Spider

Image 9

Here we have made a start on replacing the sections of coolant hose and you can see the revised version of the rubber plate in place on the base of the coolant reservoir. You can see it covers more of the surface area of the reservoir base than the original version ...

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ROTAX 912ULS Reassembling the Coolant Spider

Image 11

Note that in the usual configuration of the coolant spider there is one section that uses a formed (right angled) length of hose. This is a special Rotax part not a section of standard Rotax coolant hose ...

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ROTAX 912ULS Reassembling the Coolant Spider

Image 13

Here is the finished reassembled coolant spider with new coolant hoses attached. What may not be immediately obvious here is that the coolant reservoir body has been cleaned and resprayed to achieve an enhanced cosmetic finish. It is now ready to have hose clips replaced and then the assembly will be ready to refit to the coolant elbows ...

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