AAT Cylinder Head: Fits 1T Engine Block?

Translated on 08-10-2026, 2:30.

The probability is likely to be very high that it will work out.
Does anyone know more precisely?

1T = 2.5L TDI 5-cylinder Audi 100 Type 44 (1989 to 1990)
AAT = 2.5 liter TDI 5-cylinder Audi 100 (1990 to 1994)

The cylinder heads are not identical; the AAT engine has a vacuum pump driven by the camshaft mounted on the cylinder head, while the 1T engine does not. Otherwise, the heads should be the same, or so I suspect.

Regards,
Jens.

Translated on 08-10-2026, 2:31.

??? How does the 1T engine then create the vacuum? This pump was also used in the 5-series gasoline engines.

Translated on 08-10-2026, 2:32.

christians wrote:

??? How does the 1T then create the vacuum?

Not at all.
In the Audi 100, Type 44, the power brake booster (and other comfort functions) operate via the hydraulic system.
Starting with the C4 model (model year 1991, manufactured around the mid-1990s), a vacuum-operated power brake booster is used again.

Regards,
Jens.

Translated on 08-10-2026, 2:33.

You're right, I had forgotten, even though I had a really tough time with it back then.