Illustrated 12V Timing Belt / WP / Crank Seal / Cam Seal / Expansion Tank job. No 56k.
05-11-2007, 10:56 AM
#22
Yes
The relief valve is in place to purge any gases (air) that enter the system (due to coolant flush & fill for instance).
Because gas bubbles rise and you burp & bleep the system from the high points (the heater core valve & expansion tank mouth) the gas needs a way to escape "upgwards".
If you put the valve at 6 o'clock you'd quickly build a wall of air behind your thermostat, blocking coolant.
From wikipedia:
Modern engines are run hot, that is, over 80 °C (180 °F), in order to run more efficiently and to reduce the emission of pollutants. Most thermostats have a small bypass hole to vent any gas that might get into the system (e.g., air introduced during coolant replacement). Modern cooling systems contain a relief valve in the form of a spring-loaded radiator pressure cap, with a tube leading to a partially filled expansion reservoir. Owing to the high temperature, the cooling system will become pressurized to a maximum set by the relief valve. The additional pressure increases the boiling point of the coolant above that which it would be at atmospheric pressure.
Because gas bubbles rise and you burp & bleep the system from the high points (the heater core valve & expansion tank mouth) the gas needs a way to escape "upgwards".
If you put the valve at 6 o'clock you'd quickly build a wall of air behind your thermostat, blocking coolant.
From wikipedia:
Modern engines are run hot, that is, over 80 °C (180 °F), in order to run more efficiently and to reduce the emission of pollutants. Most thermostats have a small bypass hole to vent any gas that might get into the system (e.g., air introduced during coolant replacement). Modern cooling systems contain a relief valve in the form of a spring-loaded radiator pressure cap, with a tube leading to a partially filled expansion reservoir. Owing to the high temperature, the cooling system will become pressurized to a maximum set by the relief valve. The additional pressure increases the boiling point of the coolant above that which it would be at atmospheric pressure.
03-15-2008, 03:56 PM
#25
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Re: Illustrated 12V Timing Belt / WP / Crank Seal / Cam Seal / Expansion Tank job. No 56k.
Great post---now for some advice with mine!!Please
Audi 80 1992 2.6 12valve Avant--new in New Zealand. I bought it at xmas and its a smooth unit[I have owned 2x 5 cyl and 2x 4 cyl.]
Took a trip 900kms and siezed the power steering
pump,burnt the ribbed belt and had to be towed.
Working in the open ,I managed to get a new
[used]pump and figured out how to get it all back
together.After fitting the accessory belt I noticed that the timing
belt appeared loose.Oh no, i thought --but after starting the engine the belt tightens which tells me that it is hydraulic?Is that so, as some of my readings suggest a similar spring tensioner as the accessory drive has.
Any advice or suggestions please--I will have to get back in there,I know,but I need the kind of inf found on this forum. Thanks
Bob
Audi 80 1992 2.6 12valve Avant--new in New Zealand. I bought it at xmas and its a smooth unit[I have owned 2x 5 cyl and 2x 4 cyl.]
Took a trip 900kms and siezed the power steering
pump,burnt the ribbed belt and had to be towed.
Working in the open ,I managed to get a new
[used]pump and figured out how to get it all back
together.After fitting the accessory belt I noticed that the timing
belt appeared loose.Oh no, i thought --but after starting the engine the belt tightens which tells me that it is hydraulic?Is that so, as some of my readings suggest a similar spring tensioner as the accessory drive has.
Any advice or suggestions please--I will have to get back in there,I know,but I need the kind of inf found on this forum. Thanks
Bob
10-15-2009, 06:24 AM
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