Coolant woes

And so this post brings the blog up to date. The MX5 is currently off the road again, this time with a coolant leak. An incredibly hard to trace coolant leak.

It initially appeared as though it was coming from the oil sump which usually suggests the coolant pump. The headgasket had only been replaced in October so I thought it might have been changed. However, inspecting the receipt showed the pump was only checked. I therefore ordered a few bits from mx5parts and set to work on the job. I somehow got it all stripped down, timing belt off, coolant pump swapped and timing belt back on without breaking anything or running into any trouble. It even fired up straight away! However, the leak remained. I had taken the opportunity to do a full service though so it wasn’t entirely pointless.

Further investigation showed the leak was coming from the back of the engine. Again, nothing could be seen looking from the top, and nothing could be seen looking underneath aside from the resultant drips. Over a couple of evenings I stripped the back of the engine down and removed the first heater hose. It looked like the CAS may have been leaking oil onto this hose which could have damaged it. I couldn’t see an obvious split in the hose, but it had seen better days so chopped the end off and refitted it where the rubber was fresher. I also took the opportunity to replace the CAS oil seal. Fired it back up, and the leak remained.


So tonight I’ve ordered a new thermosensor housing and heater pipe. It’s still technically taking a punt, but there’s nowhere else it can leak from back there. Surely!

I’ll strip it back down again tomorrow evening, and hopefully the parts will have arrived the day after to get it all back and running again.

I fear I’ll be taking the landrover to France at this rate!

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