[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:

 

[mrelbe]

This slow heat problem is usually due to a premature opening thermostat. Check for correct thermostat operation and make sure all air is purged from cooling system.

 

[RKH]

There is also a coolant circulation pump (M13) which is located under the Mono-valve (Y19), difficult to see as the mono-valve is in the way. The pump is used when the engine speed is low and also for REST heating mode when the engine is not running.
You will get a AIRCO B1416 code from the scanner if that pump is not functioning. But it is not fatal as it just takes longer to warm up and the REST mode may not work.

 

[bayhas]

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.

 

[kiorash]

Folks,

some good suggestions here. The answer to the last post - the car takes about 20 minutes to get to 80c at normal running. Where can I find this Thermostat? any suggestions? looks like the monovalve and the thermostat are located close by ??

I want to ideally sort this out myself but not sure where the thermostat is located? is it easy to get to?

Is it worth putting the car on the diagnostic scanner to find the fault code?

any responses greatly appreciated.

regards

 

[RKH]

The thermostat is at the water pump at the from of the engine.
The mono-valve is near the windshield wiper and cabin air filter area.
The coolant circulation pump (M13) is beneath the mono-valve (this is not the water pump).

 

[kiorash]

Thats it! I think I probably know what the issue is.

few months ago I got a new fan belt and pulley replaced by a crap Indy. The issue was that the car was making slight rattling sounds in gear (drive as well as reverse) The Indy suggested the water pump was the issue and replaced it before going onto the fan belt and tensioner pulley. The noise is still there (bearable) but now my heating is messed up.

I think this is the aftermath of the water pump replacement.

Is this thermostat easy to get to/replace? i mean is it connected to any other parts which need to be removed to gain access? Fleebay has some for 7£ so not expensive?

Any ideas?

you guys have been great, thanks a million

 

[bayhas]

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


http://www.benzworld.org/forums/w210-e-class/1360233-pictorial-diy-thermostat-replacement.html

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...

 

[kiorash]

Bayhas you are an absolute star!

I looked at that DIY thread- I have to say that mine looks quite straight forward and bit different to yours as you pointed out. One silly question ?
I read somewhere that you would need to drain the coolant from the radiator and reservoir?

Is there any truth in that? I suppose if I am dismantling the hose then I will need to do it otherwise I will have a lot of spillage. If that is the case then the next question is ; where is the drain plug for the radiator located and is it easy to get to?

Finally any recommendations for top up of coolant?

Cheers folks all advice is extremely well received I intend to post a picture of what the thermostat on my UK spec model looks like (i mean is located at) might be useful to someone else.

ta

 

[bayhas]

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

 

[kiorash]

So no need to drain the radiator?

 

[bayhas]

why would you?

 

[kiorash]

I suppose not! because the radiator level is lower down and there would be very little spillage. General physics I suppose

is there a particular way I need to fix the thermostat i.e open or close or does it just come as it is?

 

[bayhas]

buy a new one, and put it there as pictured...

 

[kiorash]

Photo attached of the UK spec R129

 

[RKH]

Just do it with a cold engine, may be remove the cap on the tank to release any pressure, then unbolt the top and replace the thermostat.
Then just replenish any lost coolant.

 

[kiorash]

Folks the DIY will take place this weekend, hopefully will be successful.

I was just driving back from work which is about 3 miles and the heating started working immediately however was not very hot more like 23c at a 30c setting. I am hoping it is the thermostat, fingers crossed

will keep you all posted

ta