Coolant bung on back of engine

RS2000 · Postby **RS2000** » Thu Sep 17, 2015 10:47 pm

Gas just means thread can be used for gases & Tridon could still be NPT.
There is a thread called NGT (national gas taper), which is exactly same as NPT (national pipe taper).

Cheers

Roadrunner · Postby **Roadrunner** » Fri Sep 18, 2015 1:32 pm

Thanks RS2000, that's what I'm hoping.

Tbro mentioned the RockAuto site, which does specify it as 27NPT
I can't find a thread size on any other parts websites.

Still waiting to hear back from Mania and have also emailed Tridon Aus to see if they can confirm thread size.

Would rather not have to drain coolant out and then take time off work to take the grub screw to a hose shop

TrackAttack · Postby **TrackAttack** » Fri Sep 18, 2015 4:24 pm

Most aftermarket sensors are NPT threads. The thread in the head will be a BSP thread, sealed by a BSPT plug or thread. 27 or 28 is the thread count. There is 1 more thread in BSP when compared to NPT. They will feel like they can be used either way (depending on taper size), but the best option is an adapter for this exact issue.

Speedflow make this, http://www.ebay.com.au/itm/like/2816798 ... ue&viphx=1

You need the 1/8th BSP as male and NPT as female, then the NPT male sensor will seal (thread tape or sealant on all tapered threads for cheap insurance)

Roadrunner · Postby **Roadrunner** » Thu Sep 24, 2015 5:17 pm

Ok so after more investigation it is a 1/8BSP thread.
I contacted speedflow who sternly warned me that their bpst male to npt female adaptor is for pressure only. Not temperature sensors

However: In my random googling at work, I found that some MX-5's have the main coolant sensor in the back of the head, instead of the outlet housing,and later models that have a sensor in the outlet, have a blanking bolt in the original spot. (same deal as the small gauge sensor)

Checked out my SE last night and hey, there is a blanking bolt there! This will be much easier to access with a readily available 12x1.5mm to 1/8npt adaptor!

Awesome! Except, the EGR pipe is directly over the bolt head :evil:

No biggy though, I'll let Mania decide if they want to either:
Tap the small 1/8bsp hole out to 1/4npt and fit an adaptor. (coolant will need to be drained anyway so removing the heater hoses is no issue, remove the EGR pipe and theres better access again)
Or remove/modify/massage the EGR pipe out of the way to use the blanking bolt position (EGR valve is redundant anyway due to aftermarket ECU)
Or even remove and tap the heater core outlet if there's space? Im thinking not based on the ribs and lack of flat surface? May be too thin too. And again, EGR pipe squarely in the way.

Can anyone can see a problem with this?

rascal · Postby **rascal** » Thu Sep 24, 2015 6:21 pm

Roadrunner wrote:
Can anyone can see a problem with this?

I used this blanking bolt when I did my reroute on my NB8A (so BP4W head)
Just swapped the blanking bolt for the temp sensor and vice versa, and swapped the front and rear housings.
Factory temp sensor now reads from 1 inch away from where it used to.
All good 18mths on.. (though I didn't have EGR pipe to deal with. That went long ago..)