should the air valve shut off compleatly when warm

[erickmarciano]

when cold it sucks very loud and as the engine gets hot the noise goes away but when I block the air valve when hot the suction build up after about 2 seconds is it normal<I feel a litle vacum not much >?  . just replace the air valve thermostat on my 280sl and the base if the thermostat was larger I had to make the hole biger in the plate where it sits.
thanks
Erick

1971 280sl
1962 VW
1954 Allstate vespa
1958 gs150 vespa
1962 gs160 vespa

[jeffc280sl]

Hello Erick,

I recently replaced my fuel injector pump thermostat on my 1970 280SL.  Had the same issue as you regarding the plate the thrmostats sits on.  So like you I enlarged the hole so the thermostat fit snugly.  When hot the thermostat arm extends and pushes a cylindrical air valve which blocks air from coming in through the fuel injector pump air filter.  As I recall there are no o-rings or other sealing devices on the air valve.  I think this will create the potential for a very slight vacumm, especially as the air slide valve wears over time.  Given the lack of a more robust seal I think a very slight vacumm when warm is probably okay.  I'd be interested to hear what others say.

Jeff C.
1970 280SL 4-speed

[ja17]

Hello Eric,
I agree with you Jeff. A bit of vacumm leak will make very littl difference.

Joe Alexander
Blacklick, Ohio