Billet Upper Radiator 4Y Pipe (MK4 8V, 1.8T, 1.9 TDI)

Our Billet Upper Radiator Hose replaces plastic junction pipe (#1J0-121-087C) used on  Mk4 1.8T / 1.9TDI / 2.0 engines.

This part is mated with OEM upper radiator hose P/N’s :

1J0-122-101BL (1J0122101BL)
1J0-122-101R (1J0122101R)
1J0-122-101A (1J0122101A)
1J0-122-101B (1J0122101B)
8NO-122-101A (8NO122101A)
8N0-122-101B (8NO122101B) with no thermo switch.

The flimsy plastic OEM 4Y piece located in the upper radiator hose quickly dries out and becomes super brittle. If you look at it wrong, it will snap and leave you stranded. Or worse, turn your high dollar motor into an overheated paperweight. Our BILLET ALUMINUM version is made from CNC'd 6061-T651 aircraft grade aluminum. Our version is also machined to accept ORB (o-ring boss) to Nipple as well as -AN to ORB fittings for each of the 4 ports. This allows owners to use the factory hoses, or switch to complete -AN hoses for the holy grail of all cooling systems! Each fitting is supplied with the appropriate viton O-ring on the ORB end. The ports are sized as follows :

Upper (reservoir return) : 4AN
Lower (oil cooler outlet) : 8AN
Left /Right Main Radiator outlets : 16AN

This part comes as shown in the pic with all the fittings for OEM radiator hoses.  Customers may choose to order this part as the main body only (with no fittings). If you would like the part WITHOUT the standard radiator hose fittings, please contact us.  Please note the parts will be shipped unassembled - you can use a pair of channel locks with tape or other insulation to tighten down the fittings.

MK4 VW 1.8T, TDI, 8V upper 4Y
VW Golf/Jetta/New Beetle with 1.8T / 1.9TDI, 2.0 1999-2012 with upper radiator hose 4Y adapter P/N 1J0-121-087C (1J0121087C)

Audi TT 1.8T 2000-2006 with upper radiator hose with 4Y adapter P/N 1J0-121-087C (1J0121087C)

Applicable Engine Types

The fittings and ports are machined by specifically to fit the vehicle radiator hose. They match the OEM length and diameter, and thus will not cause the fitting to kink the OEM hoses. The ports adhere to the SAE specifications in all regards with the exception of length, which has been shortened. This was necessary due to the tight space constraints, which this part fits into.

This means that customers wanting to utilize -AN hoses rather than the OEM rubber hoses will need to use -AN to ORB adapters, in which the ORB side has been shortened to fit correctly into this machined part. 


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  • Model: COOL4YUPRAD
  • Manufactured by: Gruven

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