Coolant Pipe near Exhaust Manifold, Possible Leak NA MX5

ZL · Postby ZL » Fri Oct 10, 2014 5:02 pm

Hi,

I'm running into so problem today with my NA today.
I was fixing up the exhaust manifold and than i realise there was some coolant coming out of one of the pipe if i pull it backwards.
The pipe is under the exhaust manifold please look at the picture below its the one with red circle.
When i pull the pipe back its leaker at the blue arrow.

Just wondering if this is normal??

THanks

tbro · Postby **tbro** » Fri Oct 10, 2014 5:45 pm

ZL,
There is an O ring on the pipe that seals the pipe to the alloy housing.
Drain coolant, remove nut from manifold, remove pipe and go down to your local bearing place and get correct O ring, refit, refill enjoy

manga_blue · Postby **manga_blue** » Fri Oct 10, 2014 5:55 pm

It's a common fault on these engines, both in MX5s and 323s/Lasers/Astinas. It's called a heater bypass pipe or a water bypass pipe.

Remove the pipe - it just pulls out of the water pump body at the front. Check the full length of the pipe for rust and damage, especially around where the o-ring seals at the front. If it's rusted or if there's not a good smooth surface all around where the o-ring goes then replace the pipe (wreckers or Mazda or http://www.mx5parts.co.uk/water-bypass-pipe-p-991.html ). Always replace the o-ring (50c from Repco) and clean out the entry into the back of the water pipe with steel wool.

ZL · Postby ZL » Fri Oct 10, 2014 7:13 pm

manga_blue wrote:It's a common fault on these engines, both in MX5s and 323s/Lasers/Astinas. It's called a heater bypass pipe or a water bypass pipe.

Remove the pipe - it just pulls out of the water pump body at the front. Check the full length of the pipe for rust and damage, especially around where the o-ring seals at the front. If it's rusted or if there's not a good smooth surface all around where the o-ring goes then replace the pipe (wreckers or Mazda or http://www.mx5parts.co.uk/water-bypass-pipe-p-991.html ). Always replace the o-ring (50c from Repco) and clean out the entry into the back of the water pipe with steel wool.

Hi, thanks for the reply.

I haven't completely removed the pipe yet just that when i pull it back a bit it leaks little coolant. Is this how the pipe and pump is designed?
In this circumstance will i need to replace the O ring, if i replace the O ring will i need to replace the coolant as well?

Thanks

speed · Postby **speed** » Mon Oct 13, 2014 8:55 am

Yes it's normal.
As long as it doesn't leak when sitting in place bolted on exhaust stud. Wouldn't hurt to replace the o ring though as others have said

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manga_blue · Postby **manga_blue** » Mon Oct 13, 2014 9:41 am

You'll lose a lot of coolant when you pull the pipe out. Might as well flush it all out, check and replace any old hoses and replace the coolant then. Have a good look at all the little hoses that run between the back of the head, the oil filter mount, the throttle body, etc at the same time. They're really common failure points and people to get to, especially at night on a back road. You can replace those ones with stock 1/4" water hoses from Repco.