what year 2nd gens came with that coolant neck that has the cap and what model engine do they come in

 

my 88GTU has the cap on the neck it that helps

 

i have a turbo 2 and it has it on too

then i see a couple of other guys cars and they dont have theirs

 

86-88 (S4) have the aluminum thermostat housings with the caps, the 89-91 (S5) have a plastic neck without any filler cap.

 

thank you very much BANZAI

would the s5 coolant neck fit the s4 ...i want to get rid of my neck for the plastic one

 

No, it has a different bolt pattern, 3 bolts vs 2 bolts

 

I was wondering the same. As well, I noticed one of the s4 necks has no hole tapped for the Temp Gauge. Anyone know why?

 

they have a spot for a thermo, but its not all the way through, everyone i've talked to about it doesn't know why that is

 

The temp switch on the S4's neck is for the auxiliary e-fan. On S5's this switch was moved to the back of the water pump next to the ECU thermosensor. Not all FC's have this fan, so not all have the switch, buy all have the spot for it.

Guru Motorsports in Australia have cast aluminium S5 necks for A$95 (~US$70) plus shipping.

A replacement plastic neck ($62 from Mazdatrix) should last as long as the first one, and hence probably outlast the car...

 

Turbo II's and automatic N/A's have the auxilary fan, so they both have the additional thermoswitch.

 

would it be feasible to drill it on the s4 neck where the hole is and put in an aftermarket temp sensor?

 

That is what I was wondering. So, if the e-fan is removed, no need for it...