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Discussion Starter #1 (Edited)
Hello all,

I have a question regarding the coolant junction on top of the intake plenum/throttle body on the late S3/early S4 Spiders. On my S4 (Apr. 1990 manufacture date), the junction is three way (T-shaped), one coming off right by the thermostat housing, one going to the coolant reservoir, and the last one heading to the heater core. I think this configuration is unique to the motronic S3 and very early S4. The reason I am talking about this is that I am having hard time getting hot coolant into the heater core and noticed that since the hose heading to the heater core is located higher than anything else in the cooling system and most, if not all, of the coolant coming into the junction ends up in the coolant reservoir. I know that on the later S4 cars, the heater inlet hose is attached somewhere under (or by) the intake plenum but I have seen it only on pictures so I do not know exactly where it's connected. Did Alfa change this because of the heater problem I am having, or was there some other reason? I did my best to breed the system by loosening the brass in/outlet at the "T" junction but that did not cure the problem. Someone, please give me some advice or let me know were your heater inlet hose is attached (especially the late S4 owners)!!

Thank you in advance,

Edit: The first picture shows how mine looks like (the picture is of 1990 S3), and the second picture shows how it looks like on late S4 Spiders.
 

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Sorry, the only experience I have is with our '84 (S3 Spider).

I assume pic #2 is not your car. My guess is either it doesn't have a heater (?) or it is a picture someone took of a work in progress - before they re-attached the heater hose.

Why you're seeing all the coolant end up in the reservoir I don't know. Is there supposed to be a restrictor or pressure relief valve or something there? Just guessing...

Anyway, on the S3 Spider the heater hose is attached like picture #1. Then, instead of the hose that tee's off to the reservoir, there is an air bleed screw located there.
 

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I would look for the common problems....clogged heater core, disconnecting heater valve, or stuck heater valve. See if you flow garden hose water through the intake hose and flow it out the return hose. The S4 system is self bleeding. No water pump bleeder. No intake bleeder. Pull the overflow cap, fill, turn heater lever to heat, run the car to operating temp, top off coolant, replace the overflow's pressurized cap.

I believe the heater on my 92 is supplied off that big molded hose. I'll check it out and report back.

Best Regards,
John M
 
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