will a 91 water pump neck fit on my 88 im tired of the extra cap.

 

it will not work....the way the rad fill cap is mounted on the s4 is lower than the s5s.....if u swap it over u'll creat an air pocket within the system and u wont be able to fill it without that extra filler cap

 

You can if you swap to an s5 waterpump and housing.

 

huh? From what he described, I think he is talking about the thermostat housing. The S5 housing flange has 3 bolts and the S4 has 2. Gotta change the whole pump unit (pump, pump housing T-stat housing). S4 and S5 pumps don't swap, nor do the thermostat housings.

 

That extra cap is the highest point of the cooling system.
It allows you to fill coolant / water and eliminate air pockets.
Why would you want to eliminate it???


-Ted

 

Not to hijack the thread or anything, but would the s4 neck fit on a s5 waterpump, or would the whole water pump have to be changed. I'm not a fan of the s5 filler neck on the rad, and was hoping to get a s4 koyo rad to replace it.

 

The water pump housing and water pump need to be changed.
The thermostat "cover" has different bolt patterns, and they are not swappable.


-Ted

 

Yeah, I'd think thats the best place to fill the system. Ive noticed that my 88 does also have a cap there and on the rad... my friends base model only has the fill cap near the tstat however (no radiator cap...) strange!

 

does anyone have an s5 thermo housing for grabs?

 

I was thinking about making an adapter just so I could use the aluminum filler neck on the waterpump housing, the highest point filling cap is just a really nice thing. Question though. Can you put an s4 pump on a s5? That would make it easier, but does the pump pump more or less? Is it the same pump? ...lateR

 

That's a good idea, but you run into clearance problems with the now-raised S4 thermostat cover...


-Ted

 

Yeah, I thought it would be close. But it should still fit in there...

 

Also might need to make the adapter tapered so it would hold the tstat in place like the stock one does. I'm still looking into making a metal s5 replacement unit.