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Thermostat ML320

9K views 28 replies 7 participants last post by  springerfever 
#1 ·
I am beginning to wonder if my thermostat is lazy or going. While I have never had overheating issues now with the colder temps it seems to be taking longer to warm up and heat the cabin as well as seems to be about 60 maybe 70° max.
That's after driving about 20 minutes stop and go traffic in town, so it should be up to temp. So I am curious what the rating for the thermostat should be ? I found a Wahler replacement that shows 87° as its rating. I do get cabin heat and it is hot but my indicated temp never hits or comes close to 80° let alone 87°. What is everyone seeing on their gauges?

TNX!
 
#4 ·
Thanks Jim I changed the clutch the other day but haven't really been for a descent drive to check if it has made a difference. I'm doing a view Ks tomorrow so I'll keep an eye on the temp during stop and start driving. It's a hot one here again tomorrow so should be a good test. I have to be honest my cyc pump hasn't worked for about 3 years.


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#5 ·
You would also have to check the coolant circ. pump. If it is working then when the temp. reaches 80°C then go to the firewall and check the two heater hoses for temp. differences.

Then you should check the temp. differences on either side of the T-connector, as indicated in the link below. If there is a big difference in temp. feel then there is a blockage.

http://www.benzworld.org/forums/w16...l500-will-not-generate-cabin.html#post4394269

Just check things out before replacing things.
 
#6 ·
Thermostat ML-320

I didn't see weather you have a gas 320 or a CDI diesel . Two very different thermostat's . But on a gas model engine , with High mileage the Alum housing erodes where the S.S. valve seats against it. It then lets coolant weep by . Causing a longer warm up time. It is a very easy DIY. But as 43sqd indicated . Make sure the rest of the system is functioning properly. I think it is under $40.00 , for a OE part. It is made by Wahler .

One thing ,I use to do when I lived above Syracuse , N.Y. . In cold weather , at the end of the days travel , I would turn the heater controls off , Blower fan too. WHY? the heater core is a little type of Radiator too. Blowing cold as hell air across it drops the engine coolant temp. Even though the engines cooling system is in Bypass circulation mode. on 1st startup! Another thing is that the electrical system & Battery takes a 30 AMP + hit as you turn the key into the second position , And you have not even cranked the motor yet. Save some battery power reserve here . After about 5 minutes of no heating system not sucking the temp out of the coolant , You now can turn it on and get some good hot Air.
Cheers _PTEngineering
 
#10 ·
matt, first try and spell things out in words. Although I know what you mean, the abbreviation "cyc pump" is meaningless and incorrect.

Secondly, I supplied you with a quick procedure to check the condition of the Fan Clutch and you have made no mention of doing so.

Thirdly, in a very hot climate such as yours, you need a proper working Coolant Circ. Pump. They do not install components on vehicles that are useless.

How can we proceed any further if the obvious things are not checked or corrected first?
 

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#12 ·
Weird hadn't seen any notice of replies to this.

I will check out the temps around the joint later today. I just replaced the aux coolant pump back in October and it is happily buzzing for 5 mins after shutdown. That did stop the tea kettle/gurgling noises that used to happen after stopping. Our temps are usually within a few degrees of freezing in winter so not that cold at all but I was sure the indicated tamp was higher last year as well as it seeming to take longer to heat up.
 
#14 ·
That's been it. I did get the coolant tested for temp and acidity and that was ok for the season.

I actually bought the vw pump and just swapped the motor part. Didn't even have to remove a single hose. Was cold out ~0C and still only took maybe 5 mins to do.
 
#20 ·
Me bad I really didn't mean that comment to come off as bad as it might have sounded. Sorry about that if you took it the wrong way.

I blame it on being sick, could be bird flu, ebola or swine flu... And despite rumours I am not "currently" over medicated (yet!). Thats also why I haven't got back to 43 about that joint temp he mentioned I'm busy driving a bed right now.

Dave
 
#21 ·
Thats cool Dave hope you get better soon. This is not a fix but could you disconnect your circulation pump for 1 drive and see if your engine gets to operating temp quicker. It might slow the flow down a little which would then point to your thermostat staying open a bit.
Just a thought.
 
#23 ·
Ok finally crawled out of my deathbed to check the joint temperatures. The hoses and joints after about 40 minutes of driving around town were all about the same temp. The indicated gauge temps were just on the low side of 60ish. Eventually after more driving around the temp would slowly creep up to below 70. And for the first time I felt the heat increase as I accelerated down the highway. On my previous vehicles that would have been a sure sign of a lazy thermostat but not sure in this case if the system was adjusting output air temps on me when I felt that.

And Sorry again Matt if I sounded a bit in your face really wasn't intending to post like that. Must have been the 200 degree fever or the bird flu or...;-] I was technically dead but I'm feeling much better now.
 
#24 ·
Good to hear you up and about. Everything can seem worse than it is when you feel like shit, apology more than accepted.
It does sound like the coolant is traveling through the radiator to quick and cooling to much.
I would wait and see what 43sqd has to say about this one he would point you in the wright direction better than I can.
I have heard before that people who have taken their thermostat out the engine will eventually overheat because the coolant doesn't get time to cool down in the radiator. So there is a fine line between to fast and to slow.


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#25 ·
I'll wait to see 43's comments but basically will have to wait a few months for warmer driveway temps before I would attempt the change anyway. I'll just add it onto my parts order list and wait. I need to replace at least one bushing on my upper a-arm and get free shippings past a certain amount so want to order in one lump ass this isn't an emergency situation. Well not yet anyway. I know even a lazy thermostat is better than non. Have been around a few friends when younger who tried that with carbureted engines that always ran like crap as a result. Took a lot to convince them to just put one back in. Had one buddy back in the good old daze who did this with a Ford Falcon we had swapped a 427 side oiler into. He spent a small fortune on multiple custom rads to fix things but never thought to spend $5 on a thermostat.

One thing I am curious about is this gelling of incompatible coolants. I wonder if 43 can name a few types or brands that definitely should never be mixed. I have heard about this happening for years but never knew anyone firsthand that had it happen so sort of assumed it might be an old wives/mechanic's tale, perhaps from the early days of glycol based coolant fluids?
 
#27 ·
If anyone suspects that their thermostat is faulty, the best thing to do is to remove it and put it in a pan of cold water with a thermometer. Raise the temperature to boiling and watch for the expansion to appear. Note the temperature when this happens.

Of course you cannot check the full performance of the thermostat in the pan as it works at temps over 100 deg C in the car.
 
#28 ·
Ok 43 here we go:

1: The hose joint and surrounding hoses were same temp after 40 plus minutes of driving. After another 20 minutes of driving it warmed up to about 70 indicated. The heater definitely gave warmer air briefly when accelerating down the highway. That sounds more like a thermostat to me do you concur or is there something else to check?

2: You mentioned gelling in the heater core or hoses etc. What brands when mixed might cause this? I'm buying the X05/Z05 stuff (can't rem proper name) but am curious what types or brands might combine to cause this?

Hey I like birds...roasted and pan fried. As my hippy friend would say "the feathers dude the feathers" er something like that anyway... ;-]
 
#29 ·
wragie

Definately want to stick to the MB approved coolants (one of them being the Zerez G05 that is available at many auto parts)

In 2012/13 MB did change to another formulation (blue in color...as opposed to the G05 which is yellow/gold). I have heard that these two are compatable, but why risk it. Go with one or the other and dilute 50/50 (here in the south) with ONLY DISTILLED water. Regular tap water contains chemicals that can react with the metals in the cooling system.

The Zerez G05 is about $20.00 USD per gallon, readily available and an excellent choice.
 
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