Hello,
since ~3 weeks now my on-board computer is showing "Coolant! Visit Workshop!". We went to the dealer they made a diagnosis and said we need to replace the electric coolant fan because the fan itself and the module is damaged. After replacement the message on our on-board computer is still there. Now they are telling me it's a computer module what I honestly don't believe. It would cost another $2400 just for the part. So I picked the car up and wanted to get a 2nd opinion on this. The technician said he's pretty sure it's NOT a computer module because otherwise the engine light would be on but it is not. Is that true? Since MB dealer didn't replace the coolant fluid (I couldn't find it on my bill so I assume they didn't do it) I told the other technician to do so first. I'm just hoping it is something "cheap". I also could read in some threads/posts that you always should check the level of your windshield wiper fluid because the sensor for the coolant and the windshield wiper fluid are on the same circuit. But all levels are ok. So could someone give me an idea what's going on on this car? thank you very much!

 

go back, its gotta be the water pump. i got the coolant message once took off the belts twisted the water pump and could feel and hear it rubbing. also check for metal thick shavings in the coolant reservoir

 

Well the engine doesn't get overheated. The temperature still stays between 80 to 85 celcius. And what I also recognize is when I turn the engine on the fan goes on and there is the special noise as when you turn your A/C on. Could this be the water pump as you said?

 

were actually brothers in this situation if I'm not wrong. my car never overheated and gave me that message. and also i have that ac issue where it makes a clicking noise after 5 mins then stops and comes back again. this is a common issue with the evaporator system i think. glynn will clear this up when he signs on. get a local mechanic to look at it and hopefully its not serious good luck.

 

When you turn on car ignition,.... when does the fan go on? As soon as you turn on ignition key to position 1 or 2 or ignition? Which fan? The interior HVAC fan or the radiator fan under the hood? If its the radiator fan, is it in high mode (sound like a turbine engine) or regular mode. Does the car still start when the fan does on? Are there any other visit workshop messages displayed?

 

The fan (coolant/radiator) comes on after starting the engine approx. 3 sec later and the "noise" sounds like a turbine engine (it's the same sound as when you start your A/C). Neither I have problems starting the car nor there are any other visit workshops messages displayed. So what do you think? I also will get the water pump checked tomorrow. Even there is pressure on (with the belt) you can wiggle it.

 

When you start car,... do you wait a few seconds when turning key from position 1 to 2,... and again from position 2 to ignition? Or do you just turn the key in one fast motion to ignition?

Yeah,... that sounds somewhat familar. I had a similar issue,... with "Coolant! Visit Workshop!" and radiator fan going in high mode sounding like a turbine engine,... BUT if it happend when I was trying to start it (key in position 2 before going to ignition), it would NOT start. If the car was already driving when this happend, the car would slow down by itself and come to a complete stop! Like I was driving a bait car and the cops triggered the Kill Engine signal. Yeah, very dangerous!
http://m.www.mbworld.org/forums/showthread.php?t=432883

From what I gathered, the radiator going into high mode sounding like a turbine engine is the default setting,... so if the radiator fan is NOT getting any signals from the ECU-FrontSAM it just starts spinning in high mode assuming the worst,.. that the engine is overheating,.. so its a safety thing that it goes in high mode. Does NOT indicate the radiator fan is acting up, in fact its operating as designed! Don't worry,... A LOT of people have brought new Radiator Fans thinking it was bad,... when in fact it was operating as designed!

You should hook up your car to Mercedes-Benz STAR Diagnostic System and have the fault code read and cleared.

I have not had any issues in a few months (knock on wood) since I rotated-changed the relays in the frontSAM,... I think you should also check all your fuse and wriggle around the relays in the frontSAM to ensure there isn't any corrosion or too much oxidation at contacts.

 

Gawd, dealers just have no shame. It's so disgusting. They'll tell you anything just to get you to part with a stack of money. Then also it pays to be an informed consumer, and this is certainly the right place to get informed.
I wonder if the 1st shop did anything at all?
How much Dinaro did you part with the 1st go around?
Certainly it was just a sensor or something from the beginning.
I'd almost bet money on it.

 

Usually I turn the key in one fast motion. After I read your last comment I thought I'll try it step by step.
- Key in
- turn in position 1, Display says NO MALFUNCTIONS
- turn in position 2, Display says 1 MALFUNCTION (Coolant visit workshop) and when I keep this position let's say for 5 sec the fan is starting
- turn in ignition, coolant workshop message, fan goes off or turning down but is starting ~3 sec later again. Engine starts.

Well I already went to our MB dealer they hooked it up on STAR. 1st they said it would be the electric coolant fan itself and the module what is damaged. So I gave them permission to replace it bc the problem has to be solved before it gets worse and the expenses higher and higher and I trusted them specially bc they hooked it up. But surprise surprise the malfunction is still here. So they made another system check and now it should be a computer module. After I got the 2nd opinion on this problem it seems like MB wanna replace the computer module only to make the malfunction disappear without solving it. I won't go to the MB dealer anymore. They just wanna rip you off and wanna make money out of ya. For replacement of the electric coolant fan I payed $1300 incl. labor. But now i'm thinking about how to get my money back.

Your are so right! Payed $1300 incl. labor for nothing

 

When I was having my problem, when I turned key to position 2, a few seconds later it would trigger Coolant Visit Workshop malfunction and radiator fan start spinning in high mode like turbine engine. Then when I turn key to ignition, it would NOT start. Since you could get yours to start, yours is slightly different problem than mine. I always had to take the key out and then the radiator fan would stop after about 30 seconds.

You should get a copy of your first Mercedes-Benz STAR Diagnostic report from your dealer,.... its yours, after all you already paid for it. Usually, just to hook you up to STAR they'll charge you diagnostic fee thats about an hour of shop labour. Not only does MB STAR Diagnostic System read fault codes; it can also test various systems and components and recommends fixes. Thus, since it was already hooked up, MB STAR Diagnostic System should have tested your old radiator fan to see if it worked properly before they actually replaced it. I can understand a DIY-er thinking that the radiator fan needs to be replaced when it unexpectedly spins like a turbine engine but a Mercedes-Benz Stealership should have actually tested it first with their STAR Diagnostic System!

If its the computer module ie: front SAM,.... before you spend $2400 on the part,.... check the fuse and relays there! Fuse are easy to check and make sure all connection are good.

For relay, unless you know how to accurately test each relay,.... Try "rotating" the relays in the front SAM. There's about 10 relays in there, of different colour (black, grey, yellow) and size (large and small). Most have at least 2 of the same colour and size. "Rotate" the same colour and size with each other,... only the large grey is the singleton, but you can find a large grey to rotate with from the rear SAM (at rear fuse box). I would suggest you mark each relay before you start rotating them (see picture, I used x-y co-ordinate grid system). Let's say you only rotate the two large yellow relays, and the problem disappears, then you know its one of these yellow relay that need to be replaced (you can probably find another large yellow relay from the rear SAM to help pinpoint exactly which relay was bad). But if after rotating the two large yellow relays, the problem still persist, then you know its not the fault of the two large yellow relays, so rotate them back to their original location and rotate another set like the two large black relays to test them,..... repeat the process until all relays in front SAM has been tested. If it's only a relay,... then that's only about $15-50 at your local Mercedes-Benz Stealership.

 

Wanna give you a short update... The technician changed the coolant fluid today (it never got replaced before so i think it still was a good idea to do so) and made tests afterwards. No leaks. He also checked the water pump, no leaking. So he is pretty sure it's gonna be either the temperature sensor or the engine sensor. He starts replacing the temperature sensor on monday first then we will see. So hopefully the problem is solved then. But I will keep your advice in my mind. Thank you very much I really appreciate it!

 

Generally coolants should be changed every 5 years or 150,000 miles (Zerex G-05 in 50/50 mix with distilled water).

Coolant temperature sensor has been updated a number of times,.... latest should be MB Part# A000-905-07-00 (old: A000-542-51-18 / A000-542-28-18). Its about $20 and super easy to change, just becareful not to bump and break the Breather Pipe Socket (plastic nipple) (MB Part# 003-997-06-89 $7) holding a rubber hose nearby.

Usually, if coolant temperature sensor is faulty, it'll be stuck right at 80 degree Celsius, even when you just started the car and it hasn't warmed up. That said, the computer does keep track of engine start and performance, so it has an idea of what temperature to expect from temperature sensor,... when its off, that could eventually trigger a visit workshop message.

I don't know which engine sensor you're referring to.

 

If coolant temperature sensor is faulty, it will be stuck right at 80 celsius, even when I just started the car and it hasn't warmed up?! This doesn't happen to my car. When I turn the engine on the first time, the gauge starts at 0 but is increasing very fast. The technician also said that the engine temperature is a little bit lower than what the gauge on my display is showing so that's why he thinks it's the temperature sensor but he will make more tests on monday. I think I was reading the gauge wrong then. The bar stays between 80 and 100 celsius so I guess around 90's. I'm confused now. Before I drop my car off on monday I'll get a copy of the diagnosis report so he can take a look at it. Let's say it's the temperature sensor can I delete the malfunction manually with the R-button or do I need a system to do so?

If something was wrong with the computer module wouldn't I have any other problems like engine light on etc.? According to their diagnostic system the module wouldn't response.

I'll implement your advice today checking the front SAM. Where is it exactly? Under the driver seat? The engine needs to be off right? This is probably a stupid question to ya

 

zZz - I would ask the dealer why they didn't check the fan using STAR instead of replacing it ASSUMING it was bad. I would also ask for a substantial refund based on this. Absolutely NO reason they should have replaced the fan if they could have checked it on STAR first.

 

thats why if i get anything fixed i tell them save the old part...y
they say.. ok we need to replace blah blah blah..then i say if this doesnt solve my problem

i want my money back on everything (since u saved the old part) and their gunna do it

 

$1300 for a fan? We F Me! All you need to do to know if a fan is bad is apply power.
Disconnect connector, get some wire, connect to battery through whatever means.
Like how about jumper cables, then put wire from jumper cable to connector.
If it goes on, it's fine. Dumb Dumb Dumb greedy ****'s!!!!
Get the old part and put 12V on it and see if it fires up.
It's funny how little* my car has needed since I stopped going to the dealer.
Amazingly it keeps running, though I do mostly DIY, but at least I know it's being done.

*Little is relative. Aside from normal maint (and thats a fair amount), I've replaced the supercharger, cat, and rebuilt the alternator and starter. Plus flushed the tranny. But still runs great at 187K miles.
All the above is to be expected on a high mileage car.
But DIY alternator is $200 vs. I've seen people pay $1500 at the dealer.
Supercharger cost me about $400 vs. $3K at the dealer.(New one 650, sold old one for 250)
Cat about $300 vs. 1500.

 

Must be honest I was very foolish. Is fan and module ONE part or can you change them separately?
I give it a try to get my old one back on monday. Hopefully they still have it.

 

Yes, Radiator fan and control module is one unit from Mercedes-Benz. Its NOT a high fault item and many have mistakenly changed them out.

Coolant temperature sensor is quite easy to change yourself,.... on my M271, its on top right side of engine with wires sticking out near breather pipe,... just follow the hose from coolant expansion tank.

Front SAM is under hood in front of driver side near firewall,.... under a black plastic splash guard,... you'll find a black plastic box with 2 clips,... it's in there. Car can be on when checking fuse,... checking as in electric probe testing for power at 2 top connector of fuse. If you're pulling out fuse or relays, car should be off,... with key out of ignition.

I don't know what R-button is.

 

Alright thx, I will check them out tomorrow. I was just waiting for your answer
R-button is the reset button on the left side of the dashboard.

 

Checked all relays incl. wires...Warning didn't disappear...Temperature sensor gets replaced today so keep the fingers crossed...

 

Car was 2nd day at the workshop. All tests were done plus changing temperature sensor, checking water pump and relays incl. fuses, replacing fluid etc. and we still have the same warning on our computer. I think he was trying to delete it with his system but it still appears on our computer. I'm getting so tired of it. Do you have another idea what it could be? Maybe it's really a computer module? But wouldn't I have more problems with the car then? I just don't know what to do anymore. It's so frustrating :/ It must be something wrong on the circuit between A/C - electr. coolant - dashboard...

 

I also just started getting the "Coolant - Visit Workshop" message and have scheduled to take it in on Friday. My warning only goes on after the car has been driven for quite a while and when it is warm outside. Drove over 50 miles this morning before it came on and it only did so after sitting in line at a drive through for a few minutes at idle. The temp gauge goes just above 80*c and the warning comes up. Checked the resevouir level and it was fine. I also don't hear the fan running at high speed. Seems like as long as I keep the car in motion the warning does not come on.

One thing I did notice is that when I had the car in park with the engine running, the message would go on and off and each time, I could hear something change, like a slight clicking sound right before the message came back on.

I do notice a high pitched whine when I turn on the A/C but that comes and goes and may or may not be related. The A/C is not puting out very cold air either.

Any ideas as to what is causing this? Oh, and my car has 104k miles and is an '06. Radiator has not been flushed before if that makes any difference.

 

Lengthy update: Decided to experiement a little today and found out that the coolant fan is not running, but it gets weirder. Started the car this morning and the temp gauge is on zero degrees. Have A/C and vent fans turned off. Drove to work approx 12 miles and no sign of the warning message. Noticed that when the temp gauge got slightly over 80*c, it suddenly dropped a few degrees indicating that the thermostat is working. Temp never got more than slightly over the 80* mark but did not sit in any traffic so the car was always moving.

Went out for a couple of appointments and lunch and started off fine. Drove approx. 10 miles on the highway and no warning light. Temp still right at 80*c. Drive another 15 miles to next appt. and all is fine. Still don't have the A/C on as it's only 79* this morning. Get stuck in some construction traffic and bam, warning light comes on and temp goes up to maybe 85*c while sitting in traffic.

After an hour at the appt., leave and message is gone again and stays gone until I get off the highway and have to sit at a stop light. Within 15 sec. the warning comes back on. What's weird is that during the 20 mile drive this time I had the A/C on and it was blowing ice cold, no warning, temp gauge at 80*, etc. etc.

Get off the highway and once again, warning message comes on and the A/C blower picks up in speed by a few hundred RPM and the ice cold air turns to room temp. Is there something in the computer than automatically cuts out the A/C pump when the coolant temp reaches a certain point?

The plan for tonight is to check the fan motor first by applying voltage directly to it. If it runs, then look for a possible bad relay. After that, I'm lost. Anything else I shoud check before taking to the dealer tomorrow?

Things I've ruled out so far:
- Thermostat -temp gauge drops a few degree right after engine gets to operating temps
- Water pump - if this was bad it would likely be making a noise and the temp would be much higher than 85*c
- A/C refrigerant - Blows ice cold when the warning light is off

Oh, and how easy is it to replace the fan and what should a new one cost? I've read where dealers charge as much as $1200 for a new one and that is just not in the budget. Part #'s and source would be very helpfull.

Thanks!

 

As weird as this sounds, I had a 1995 Volvo in which I could connect a jumper to where you read the codes and it would cycle various fans under the hood. I do not know if this is possible with MB vehicles?????
Mike T.

 

An update to everybody who has exactly the same problem... We finally found what it is... It's a damaged wire in a wiring harness going from the coolant module to the a/c control unit inside or from the coolant module to the computer.