Replacing heater hose.

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Just had my 94 drop a heap of coolant on the ground :(.  Looks like the
problem is a short heater hose, running from the firewall, to the back of
the head, underneath the cam position sensor.  Problem I have is getting to
the head end clip.  I can see it, but barely touch it, does not seem
possible to get a pair of pliers in there. It would seem it was attached at
the factory before the motor was put in.  I really don't want to undo the
engine mounts here.

Anyone done this before? Know any tricks?



Re: Replacing heater hose.


i'm no expert, but this is what the enthusiast's shop manual says (grainger
/ shoemark, veloce publishing)...
9.  A metal pipe runs back from the coolant inlet casting, the back end
being secured on one of the exhaust manifold studs.  This is the heater
return pipe, the hose connection to which can be accessed at the back of the
engine compartment.  The other end of the hose connects to the heater outlet
stub on the firewall (bulkhead).  The heater hoses are easy to reach at the
firewall end, and are secured by the usual clips.
10.  The heater inlet hose is connected from the outlet cover on the back of
the engine block to the heater inlet stub at the firewall.  Access to the
engine end of this hose will require removal of the ignition coil assembly.
The outlet cover itself is retained by one 12mm nut, should removal be
required.  The cover also carries the water thermosensor.
hope this helps... and i suspect your next question will be how to remove
the ignition coil...
ps. now is a good time to replace the rubber grommets on the firewall too.


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Re: Replacing heater hose.


That still sounds like a pain in the _ _ _!

Good luck Mal,
Chris
99BBB

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Re: Replacing heater hose.


Mal Osborne wrote:

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The way to do it is to remove the coil pack first - not the easiest job.

If you haven't already done do, change the CAS O-ring first.  This is
usually what causes the hose to fail; oil dripping on it.  The O-ring is
another PITA to do; I did one yesterday morning.  The problem is getting
the dogs on the sensor to line up with the slots in the end of the
camshaft.  It can be hard to tell the difference between the resistance
from a misaligned CAS and the resistance of a new O-ring, so keep trying
and remember it might need a bit of a shove when it is lined up
correctly.  A little mirror is very useful so you can see which position
the camshaft slots are in.


Re: Replacing heater hose.


OK, getting there.  Removing the coil pack took things from impossible to
merely difficult.  The factory spring clips holding the hose on are still
fitted, was difficuly the get pliers in there.  Might be easier once I get
some worm screw type clamps instead.

Looking at the end of the hose, it certainly looks like the CAS seal is
shot, I am off to research how to do this at Miata . net.

Thanks guys!


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Re: Replacing heater hose.


OK, all done! Been for a test drive, trying to determine if 6500 or 7000 is
a better shift point :)  Was a fairly straightforward job thank to the hints
here & at Miata.net. The CAS seal was indeed shot, had the sealing
characteristics of bakelite.

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