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Hello everybody :) I own a 2014 CLA 250 ~ 75 000 Km , mods I did related to the engine are AEM intake , Turbokits BOV spacer and a Muffler delete.

So around 8 month ago I got a CEL saying my thermostat need to be replaced , the cooling temperature was always 60 Celsius and it take a really long time before it reach 80-90.
3 month ago I changed my thermostat , I bought a genuine one on Ebay since it was cheaper than buying here locally in Montreal since the price here are double.

Driving around more than month it was fine , the temperature went to around 90-95 and stayed there and then one day the weather was really cold and my car was stuck in the ice so I couldn't drive it for like 4-5 days.
When I drove the car after 4-5 days sitting in the freezing cold after not even 10 min I got a warning saying " coolant overheat " ( heating was working ) , I check the engine , everything was cold , the pipe , thermostat , ...
I left it a few days in my garage and inspect the engine , no coolant leak everything seems fine. I turn on the engine and let it run until it reach operating temperature but this time Heating is not working , there was no coolant pumping from the Aux water pump to the radiator , only blowing out cold air and then the cooling overheating. I decide to change the Aux water pump and everything work fine , heating and no more overheating.

But the next day the problem came back but this time heating is working and engine is overheating , but the engine is just warm

So I unplug all the coolant pipe through the radiator and re-plug them , the car went back to normal .

The next day it happen again , not even 10 min the car is overheating but suddenly the indicating temperature drop to 40 and then slowly went back to 90-95 and stayed there. That was around 3-4 weeks ago. Until now the car temperature seem to work properly stopping around 90-95 ( the arrow sometime move a little bit around 88-95 )

So what happen is when I cold start the car , after like 5 min the temperature is almost half way . Now the temperature take around 10min+ to be around halfway and then reach 90-95 by around 15 min.
Sometime at a stop the temperature is at 85-90 and then when I start driving it goes up to 95 and stay there

Before I got the CEL I never monitor my temperature , the only time i check was when I drove to Toronto from Montreal and it usually sitting around 80-85.

I'm scare that the problem will come back randomly while im driving on highway or somewhere far ...
I was thinking maybe the thermostat i bought was defective , but i never got a CEL since then and maybe my water pumps is bad but if so why my car run normally now ?
Can you guys share what indicated temperature you have ?

If anybody know or experience anything about this please share it in this thread ! 馃檹
 

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How well did you burp the supposedly hydraulic water loop system?
Sure the tsat is not sticking? Despite being new things do happen
Some ebay parts cheap cuz old stock thats been superseded ... check its p/n against online benz parts store etc
 

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Discussion Starter #3
How well did you burp the supposedly hydraulic water loop system?
Sure the tsat is not sticking? Despite being new things do happen
Some ebay parts cheap cuz old stock thats been superseded ... check its p/n against online benz parts store etc
When I first got the problem , there was some burping in the coolant reservoir and I just let the engine run and you can see some air bubble. I left my car at a mechanic and he said he just unplug and then re-plug pipes that are connected to the radiator and he said there was air pocket . You may be right about the thermostat , I don't know if its the thermostat or the water pumps causing all this , since no CEL and before I changed my thermostat I never had this problem. The ebay p/n is the same as mercedes , I receive everything in a Mercedes part box. This is the ebay product I bought :

 

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Hmmm ... thats not burping till hydraulic
Which can leave bubble groups running around
Aside from causing localized spot heating so causing latent stress cracks from transient thermal gradients (ie issues show up after warranty) air pockets instead of fluid at the tstat and water pump will yield cavitation and its a vicious circle
The reservoir is a hot tank so air pockets in the cold loop will never get out then maybe some chance after the mixing occurs but as noted above the bubbles loop is a tough one
This thing with the water pipe r&r is supposedly monkey business that works most of the time though clearly it was not a remedy for you
I suppose a 4hr idle run with a mild fan gunning the radiator may create enough chances for the tcycling to herd all the bubbles out ... but since air pockets like to sit at high cavities and you cant roll the engine around it may still not be perfectly hydraulic
Somehow air got into your system in the first place so despite all these parts changes and fixes you may still have a suction point somewhere ... like a pool pump with a tiny tiny lid seal leak
Sorry for the pope talk hope you figure it out!
 

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Discussion Starter #5
Hmmm ... thats not burping till hydraulic
Which can leave bubble groups running around
Aside from causing localized spot heating so causing latent stress cracks from transient thermal gradients (ie issues show up after warranty) air pockets instead of fluid at the tstat and water pump will yield cavitation and its a vicious circle
The reservoir is a hot tank so air pockets in the cold loop will never get out then maybe some chance after the mixing occurs but as noted above the bubbles loop is a tough one
This thing with the water pipe r&r is supposedly monkey business that works most of the time though clearly it was not a remedy for you
I suppose a 4hr idle run with a mild fan gunning the radiator may create enough chances for the tcycling to herd all the bubbles out ... but since air pockets like to sit at high cavities and you cant roll the engine around it may still not be perfectly hydraulic
Somehow air got into your system in the first place so despite all these parts changes and fixes you may still have a suction point somewhere ... like a pool pump with a tiny tiny lid seal leak
Sorry for the pope talk hope you figure it out!
Hmm , maybe air got inside when I replaced the thermostat ... Until now , about a 2-3 weeks , there is no more problem I just hope it stay like this. But in your experience do you think the water pump or the thermostat are causing this ? There is no noise coming out of the water pumps and no CEL so Im guessing everything seems fine ? Also the temperature, is it normal to be around 90-95 C ( sometime after a stop the temperature would go down but if driving on the highway it seem to stay somewhere around 95 ? Before that my thermostat got stuck open I remember the temperature being around 80 and stay fix there . Base on my other Benz , my 2002 E320 temperature is usually around 78C and stay fix there , my 2008 ML550 is usually around 85-90C.

There is also something I notice since changing the thermostat the " Start and stop " logo stay yellow even after the temperature went past 80C and I need to drive like for another 30 -45 min for the " Start and stop " logo become green. But a couple days ago the temperature went to around 78-80C and the logo became green ( I think it suppose to be like that to be normal ) it happen only once until now

Do you think because I took too long to change my thermostat that the computer kinda got confused ? because I was always at a operating temperature of 60C with a stuck open thermostat.

Something to add its that with a low operating temperature your engine will run rich and when I drive in indoor parking I use M mode and just drive around in 1st gear and you can hear the crackle and pop . Now with operating temperature at 90-95C there is only some low crackle which mean that the engine is running efficiently.

I'm just so lost now , the only thing that bother me is that I dont know if this will happen again ( I really hope not.. ) imagine going on a long trip or driving on the highway and your engine overheat.

But all of this happen after I let my car outside in cold freezing weather for a few days i dont know if its because of the weather something froze or the electronic going mad ...
 

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Well ... no more issues is a good thing
Though good idea to get cheap obd reader and log coolant temp to see the temp swing data
 

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I have this problem at the moment. Drove a 1200 miles trip. When I drove in the city the temperature was around 90 but going on the highway it dropped to 70-75

temperature of the engine was ok. Coolant temperature was also ok

what do you guys think? My thoughts: when the meter is not going to overheat temperatures it鈥檚 not bothering me
 

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Discussion Starter #10
I have this problem at the moment. Drove a 1200 miles trip. When I drove in the city the temperature was around 90 but going on the highway it dropped to 70-75

temperature of the engine was ok. Coolant temperature was also ok

what do you guys think? My thoughts: when the meter is not going to overheat temperatures it鈥檚 not bothering me
After the temperature go down to 70-75 , will it go back up to 90 after ? or stay there ? Honestly , 70-75 is not that bad but its still better if you run around the normal operative temperature ( which is around 85-90 something ? ) the only problem is that you will run a little bit richer , which will affect the MPG but as long as the engine doesn't overheat its safe.
 

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After the temperature go down to 70-75 , will it go back up to 90 after ? or stay there ? Honestly , 70-75 is not that bad but its still better if you run around the normal operative temperature ( which is around 85-90 something ? ) the only problem is that you will run a little bit richer , which will affect the MPG but as long as the engine doesn't overheat its safe.

It goes back indeed. And what about the mpg I did not noticed any.

however the temperature can鈥檛 all of a sudden go back from 90 to 70 in 3 seconds because the meter drops in 3 seconds. Impossible. So don鈥檛 drop to much attent to it. If the meter wasn鈥檛 there you wouldn鈥檛 even mentioned this in this topic
 

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It goes back indeed. And what about the mpg I did not noticed any.

however the temperature can鈥檛 all of a sudden go back from 90 to 70 in 3 seconds because the meter drops in 3 seconds. Impossible. So don鈥檛 drop to much attent to it. If the meter wasn鈥檛 there you wouldn鈥檛 even mentioned this in this topic
You can try to connect an OBD 2 scanner and monitor the temperature while driving. I did this after JMC suggested it. What I found is that the coolant temperature on the scanner was always 10C behind . When on the gauge is 90C , on the scanner its 78-80 C. Gauge stay around 90-95 and the temperature keep going up until 90-95. After both reading stabilize , on the scanner I found that my coolant temperature is around 91-100C +/- 1 , but its mostly stay around 92-97. Temperature never went past 100C
 

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Glad its working
Sometimes the data logs do not correlate directly with the gauge for some reason though from plots and measurements the obd data makes more sense (at least most of the time)
And yes for normal conditions max 100c is typical with cycling ranges somewhat lower as what you noticed
 

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Glad its working
Sometimes the data logs do not correlate directly with the gauge for some reason though from plots and measurements the obd data makes more sense (at least most of the time)
And yes for normal conditions max 100c is typical with cycling ranges somewhat lower as what you noticed
Okay I see perfect
 
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