Well I bought a clean, used radiator from a member here on the forums, and I'm quite happy with it. It came clean and everything, barely any bent fins, almost brand new. The problem is, there's a 3rd hole on the upper drivers side of it when it would be in the car.. I looked up the PN (15-2000-N350) and it's an S5 radiator. Judging from the pics I've seen, and the S5 FSM, I need to buy another filler neck and cap, but I'm not sure of what else. Any suggestions?

EDIT: I drive an 87 GXL, stock minus intake and exhaust mods.

 

if anything, you might need to get the plastic piece that goes under the filler cap without an overflow nipple on it.

 

How would I bleed the air out of the system then, since this new rad doesn't have the bleed screw that my S4 rad did.

 

you dont need to bleed s5 radiator becuase the filling point is higher than top of the radiator and s4 filling point.

to get the air out, PLEASE do this when THE ENGINE IS COLD or be extremly carefull. im in no means liable for your injuries.

cover the radiator opening (filling point) with your palm or with rag and keep squeezing the upper radiator hose.

this will allow the air from upper hose move towards the top of the radiator.

repeat the process untill you feel more resistance in upper hose while while squeezing.

 

Well, I'm confused now, because in the S4 radiator, the filler neck (attached to the water pump) was the highest point, or at least I thought it was the highest point. The problem was the upper radiator hose has a bend in it which allows a pocket of air right where the bleeder screw it normally located.

So just squeezing fixes this on the S5 rad? Do I need a new neck and radiator hose for the upper assembly? (water pump to top opening of radiator)

 

s5 doesnt have filling point at the thermostat housing.

squeezing the hose will move the air pocket you're talking about towards the filling point on the right of the radiator.

 

Awesome, thanks.

 

I know this is a old thread but....

I have a s5 motor, s5 front cover, s4 manifolds/turbo/emissions, and a s4 radiator.

I have a s5 thermostat neck because the bolt patern is different between s4 and s5.
My coolant sensor that was in the s4 top filler/bleeder cap neck is now in a custom pipe, tapped, and threaded into the upper radiator hose. I can squeeze it on and off for half an hour and still get bubbles out of the bleeder funnel/radiator cap that I have hooked up.

The motor's already in so swapping the front cover isn't an option.

Would I be better off making an adapter to go from 2 to 3 bolt on the thermostat housing so I can use the old metal filler with bleed cap or getting a s5 radiator and the drivers side bleed tube atachment?

 

If I went with a s5 radiator I could put the coolant temp switch in the lower radiator hose with an adapter. My problem is I have a 1400-1600 rpm rapid surgig because there is air in the system and I cant get it out. I got a new clutch kit when I put the motor in, everytime I go into gear I can tell I'm wearing it faster....

Any input would be appreciated.

 

sounds more like a vacuum leak.

they way I get the air out is just leaving the cap off the neck until the car warms up and gradually add water between small revs.

 

It's not a vacuum leak. I've already gone over the whole thing with a leakmaster uv smoke machine. There's air in there and I need to get it out.

Does anyone know how the thermostat sits in there? (don't have the pipe here with me). I was thinking a 3/4" laser cut flange, then thread it for s5 on pump side, and s4 on upper hose side. That way I could keep my original temp sensor setup and have the top filler neck.

Would I run into clearance issues (bevel it, etc... or could it sit straight in there?


Another question, should I use a s4 or s5 thermostat? They have diff opening temps.

 

If you're going to the trouble of making such an adapter, you needn't limit yourself to the original thermostat cover.
Lots of cars have the features you require- sensor bung, filler cap- with a lower profile and better orientation (i.e., straighter hose path- especially if you've switched to an efan and no longer have to clear the waterpump mounted thermofan).
In fact, if the adapter plate is 3/4" thick, holes for temp sensors/fan switches could be incorporated directly into the flange, which opens up the options for the alternate neck even more.

Whatever path you pursue, here's a tip...
Use studs instead of screws for the upper hose fitting.
This will save wear and tear on the threads (I'm assuming the adapter will be aluminum) and allow for worry free replacement.