Faulty
Hose Composition leads to Smelly Audi A4 Quattro wagon
Eric Seifert, Automotive Technical Editor
As a nature photographer, Dan racks up over
25,000 miles a year on his 2003 Audi A4 ® Quattro ® wagon.
On a trip last week, he noticed an odd smell from the car, so he
stopped at a shop to get it checked out. He was told that the coolant
reservoir was cracked and needed to be replaced. Not satisfied with
this diagnosis, he later drove to our shop. We performed a pressure
test on the reservoir and discovered that the hose between the coolant
reservoir and the engine was weeping coolant through the hose material.
 If
the coolant reservoir appears to be leaking, the technician should
also check these possible leak sources before replacing the reservoir.
- May be caused by the
coolant hose (1) between coolant reservoir and radiator or the
coolant hose (2) between coolant reservoir and engine which may
have internal cracks (Image 19-A116).
- Internal cracks can
cause coolant to get inside the coolant hose material and leak
from connections to the coolant reservoir (arrows) due to the
capillary effect.
The following tools (or equivalents) are required
to complete the diagnosis: VAG1274 Cooling System Tester, VAG1274/8
Adapter and VAG1274/9 Adapter.
Applicable Vehicles:
2001 to 2006 All Models, All Engines
 Repair
Procedure:
(Review safety procedures in the ALLDATA
® system before beginning)
Before replacing coolant reservoir:
- Check if coolant hose
(1) between coolant reservoir and radiator is leaking at connection
to coolant reservoir (Image 19-A116).
- Replace that coolant
hose if necessary.
- Run engine or drive
vehicle until coolant reaches a temperature of 80Run engine or
drive vehicle until coolant reaches a temperature of 80°C (176°F).
Coolant reservoir, checking for
Leaks:
- Remove filler cap on
expansion tank.
- Install tester VAG
1274 and adapter VAG 1274/8 shown in
diagram (or equivalents) on expansion tank.
- Build up a pressure
of approx. 1.0 bar with hand pump on tester
- If
this pressure is not maintained:
a. Trace and repair leaks.
 b.
Check if any coolant leak around coolant reservoir still
exists.
Pressure
relief valve in filler cap, checking:
- Screw filler cap onto
tester with adapter VAG 1274/9 shown in diagram
(or equivalent).
- Install hand pump and
build up pressure.
- Pressure relief valve
should open at 1.4 to 1.6 bar.
- Replace filler cap
if necessary.
DO NOT replace coolant reservoir if there is no
further coolant leak detected around the coolant reservoir.
Written by ALLDATA Technical Editor, Eric Seifert.
Eric is an ASE certified Master Technician and Engine Machinist.
He is a graduate of the De Anza College Automotive Technology Program,
with 20 years of independent shop and parts store experience.
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