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SL320 Heating Problems

4786 Views 16 Replies 4 Participants Last post by  kiorash
Greetings Folks,

As the title suggests - My 1996 SL 320 is taking too long to kick in the heater from cold start. Sometimes up to 20 minutes. This was ok in the summer but come winter I will find this extremely painful.

Tried a search here and other forums but there is not much on heating issues. Any ideas or pointers will be appreciated. Hoping to get this sorted myself.

many thanks:surrender:
1 - 5 of 17 Posts
as everyone suggested, theromostat is the first place to look...

it is one out of two, either overcooling, due to a thermostat stuck open, or heater core not getting hot water, due to a sticky mono valve...

a good question to decide between these two causes:

Does the car take forever to get to 80* as well (normal engine operation temp)?

if yes, look at the thermostat first.

if no, look at the mono valve first.
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yes, the thermostat is fairly easy to access on the M104, 320.

it will be in front top of the engine, here is a pictorial DIY

your intake could be a tad different, but the main concept is the same, the thermostat is in a housing with 3 bolts, 10-13mm each, depending on the year.

make sure you do the job while the car is absolutely cold, preferable after sitting all night, otherwise, you will make a mess, and could burn yourself...

it sounds like your thermostat is either damaged and stuck open, or not there all together...
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that's why I suggested cool engine, because it keeps spillage to a minimum...

none the less, prestone yellow stuff works to top off any system, otherwise, the dealer will have the MB coolant
why would you?
buy a new one, and put it there as pictured...
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