broken thermostat?

[mitch_f1]

You should slowly see it opening as the water gets closer to 88*C, yes.

You get rid of an air pocket by holding second gear going around the block, and then bleeding the system with the engine running. This will ensure all the little air pockets become one big air pocket, and bleeding it gets rid of this one big air pocket.

That little hole is essentially a dribble hole, yes.

This video provides a good demonstration of thermostat function:

[evil_weevil]

thanks for the vid Mitch!

one thing I cannot work out - is actually removing the thermostat from both housings!

[evil_weevil]

also,
what thermostats do you guys run? 82 degrees? 85? 88?

I'll replace both - I just dont know what size the after market one is ie - like are NA8's same as NA6?

I just need 2 thermostats and 2 gaskets, and bingo

[mitch_f1]

I've never really looked into the re-route option, but it seems really funny that you would have two....

With two though, I imagine they would need to be exactly the same rating (off the top of my head OEM is 88*C). For gaskets get the genuine one, and chuck out the aftermarket ones.

[sailaholic]

Even with a re route you should only have one thermostat

Sent from my GT-I9100 using Tapatalk

[project.r.racing]

2. the factory thermostat has "BP05 NTC 85-88degrees" so I assuming thats the part number + temp range?

BP05 is the identifier for the MX5 NA8 head. BP05 was also the head identifier on other Mazda models of a similar vintage using the BP (1.8 ) motor.

Confirmed. BP05 is the head design + engine they ripped from another model car and put in the MX5.

85-88 is the openning temps of the 2 valves. small one = 85deg, larger 1 = 88deg. you might even find a giggle pin in there also. little brass thing that wiggles loosely in a small hole. the giggle pin is too allow air to pass through the thermostat.

i remove air pockets by running the engine leaving the radiator cap off and squeezing the upper radiator hose causing a pumping effect every 15 seconds while filling. you can see the bubbles popping out the holes where the cap should be. once the bubble stop, then air pockets are gone.

[evil_weevil]

thanks for the reply guys

this is the reroute I have - http://mx5mania.com.au/product1662.htm
infact thats mine there - my car!

so would I be better getting the same thermostat as the one as you described - project r racing? which is the one I have as the original one?

[project.r.racing]

cannnot anser that question. the pics are unless as it doesn't show the whole system.

the cooling system should only need one thermostat, but then i do not know the route of the coolent with a bypass kit fitted, so it may need two thermostats.

[eskimo]

How did you get on Mr Weevil, obviously a very patient man, interesting system you have there, it will be a sh*t of a thing to bleed though
with two t/stats. If I could make a suggestion re bleeding. Commonsense says the fluid must displace the air but air must be able to leave the
system so the first thing I'd suggest is when you decide what thermostats you are going to use make sure you remove the small jiggle pins. They
are supposed to assist with bleeding the system but just don't seem to work. The small hole left behind will NOT make a measurable difference
to the overall running temp & I have on the odd occasion run an 1/8th drill through the hole to further assist bleeding. When fitting the t/stats the
hole MUST be at the top. Now with the system you have I would suggest removing the top hose from the front (original) t/stat housing and the
front hose off the secondary t/stat. If you can block off both of these hoses or hold them ABOVE the level of the radiator filler neck whilst filling
the radiator the coolant will flow through the radiator, up through the block and eventually out of one of the t/stat housings, once this happens then
with your third hand block this t/stat outlet and keep filling till it starts coming from the other t/stat outlet. once this happens you can quickly lower
and fit the hoses and finish filling the radiator, do up the hose clamps and run up to operating temp. It isn't nessassary to leave the cap loose as all this will
achieve is to loose coolant, once operating temp has been reached and your happy you have actually (We hope) fixed the problem allow the engine to cool
THEN check and top up as ness.

Sorry about the long post, hope it is of some help.

[evil_weevil]

hey guys!

so played around with the car on sunday.
ended up replacing both thermo's to 2x 82 degrees as both my thermstats originally looked different so Id assume they had different temps...

also fixed the wiring for my oil pressure gauge, well..a mate did

did the coolant thingy for airpockets too - thanks for the tips

took car for a drive and came up to temp nicely and after 10 mins no flutter on dash board gauge for water temp.
although it wasnt "hard or spirited driving" so one evening if its dry will go for a longer drive and see how she goes.

thanks for all the replies and tips people

[mitch_f1]

Make that one evening tomorrow night, and make the destination the Max Brenner in St Ives ;)