Having heater issues with my 91 560SEL. The heat takes very long to get really hot when the car is at operating temperature but most of the time just cool to luke warm air blows through the vents. I had recently changed the coolant been probably 2 years already with the xerex yellow. I am leaning either towards the monovalve or aux waterpump? Any suggestions would be great.

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2001 E55

2001 E320 Sedan

2001 Subaru Legacy

2006 SLK280

2016 Subaru Outback 3.6

Monovalve.

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Peach Parts W124.128 User Group.

80 280SL
85 300SD
87 300TD
92 300D 2.5 Turbo
92 300TE 4Matic

From experience I also think it's the monovalve, split rubber diaphram, new insert is about $45 here at Fastlane, call Phil.


Ben

I think it is the monovalve as well. You can removed it and check to see if the diaphram is torn. Just make sure the engine is cool when you do it.

Had the same problem with my 420 SEL and it was the monovalve.

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"It's normal for these things to empty your wallet and break your heart in the process."
2012 SLK 350
1987 420 SEL