str8ridin

So the wife calls me at work and says that the car has a CEL light on and is overheating. Apparently it said "Coolant Stop, Engine Off." She also said that the engine temp gauge on the right was maxed out and there were no bars left. So, she pulled over and waited for me to come. By the time I go there (about 45 minutes later), I started up the car to replicate the issue and the CEL was off and the temp gague was right where it needed to be. So, I was able to drive it home.

Was that a sign of a water pump failure? I have the OEM pump. Any help would be appreciated.

jangy

I doubt it. The pump we talk about is the SC cooler, not the one that runs through the radiator. You have a standard water pump on your motor front, so there should be no intermittant issues. Check the pump and see if it is leaking. Next is thermostat sticking, I think. No warranty?

str8ridin

Warranty just ran out. I looked under the car and did not see any leak, nor on the front anywhere. I'm baffled...this has never happened before. Would this malfunction be logged somewhere? Is it worth it to have them run a diagnostic?

Max.H

Are you low on coolant? Check your overflow reservoir and add if needed.

lane_change

Well, I am no MB mechanic, but I would look for a faulty water temp sensor. Normally on cars, if the gauge spikes and nothing is obviously wrong, the sensor is bad/going bad. My E55 did that with the oil level sensor, it had randomly shown an oil level malfunction, but one day everything just went red, and it told me to turn the engine off, and all that...I had it checked and it was the faulty oil level sensor. Yours will not be the coolant level sensor, since that does not control the temp gauge. So I would look into the coolant temp gauge if it were my car. Probably an easy fix.

str8ridin

Just went down in the garage and checked - Nope, not low and topped off and bluish color.

str8ridin

Good point. She said that the car drove just fine too. Then again, if the wheel fell off, she would think the car still drives fine. She has got to be the slowest E55 driver on the planet too.

blackbenzz

Replace the tstat. PTE has some low temp ones

str8ridin

Drove the car tonight for about an hour and it was fine.

But, consensus is that it's the thermostat. So, I'll order a new one.

Anyone know how to replace one?

bobgodd

Someone may have to correct me here but I believe that a thermostat failure is just that, a failure. A thermostat is a mechanical device that reacts to temperature, so either it will open or it won't.

If you don't smell coolant or see a bunch of smoke, it's probably not overheating. Maybe a coolant temp sensor?

Not that a new thermostat would hurt... But this is just my understanding of thermostats.


Also, maybe check for the code that threw that CEL??

str8ridin

The weird thing is she can't remember if it really threw a CEL. I just assumed it did. But she knows for sure that it showed a temperature gauge in the IC and said "Coolant Stop, Engine Off" with the temparture bars maxed out.

So, if a thermostat is broken....it's broken and won't work at all or can intermittently?

Either way, I'll go to autozone to see if they can pull any codes in the morning.


uh, all this time I had a warranty and nothing happend. The month it ends....

CWW

I think you should replace the coolant temp sensor first. The odds of it being the thermostat on a car that's only 6 years old are very slim. But I've replaced temp sensors (and pretty much every other kind of sensor, too...all these "made in china" Bosch electronics are pretty sketchy lately) on 1-year old cars before. So I think, odds are, it's probably the sensor not the t-stat.

But with that said, Patrick at PTE is a great guy and you should give him some business and pick up one of his cooler t-stats anyway. He is one of the few vendors that are just 110% customer-service oriented. He made me a set of custom t-stats for my M120 V12, in 71c and 78c temps, so now I have a summer one and a winter one. He had to machine one of them almost entirely from scratch, using a vernatherm he wound up having to order from germany, and after all of that he still stuck to the original price quote! You can not do business with a better guy.

Also, speaking generally, newer benzes run too hot anyway. They jacked the operating temps up because it's a lazy way to meet emissions specs. But it's not good for the motor, it's bad for performance, and it's bad for all the plastic stuff in your engine bay as well. There's no operational reason a motor should be running much past 78-80c, and when it heats up beyond that it gradually starts pulling back timing (and power). A cooler t-stat is a nice thing to do.

regor60

An overheated car isn't going to return to normal temp in 45 minutes anyway, especially when not moving, so that was a sign a sensor was to blame

str8ridin

P0128 - Coolant Thermostat - Coolant Temp below thermostat regulating temperature.


Dang, it looks like a code for the thermostat, but seems like it eludes to the coolant temp sensor.

From what you guys are saying, I think I will start with the sensor first. Just drove it again today and she stays around 90 C.


CWW - Thanks. What ever i end up buying, I'll go with him.

CWW

It's definitely your temp sensor, dude. Don't waste time with anything else.

First you get a warning saying it's overheating, now you get a code saying it's not warm enough. It's 100% the sensor.

str8ridin

You are right. Let me shoot a note over to Patrick at PTE and see what he has to offer. I guess, while I'm under the hood, I'll get it a little cooler as you suggested.

CWW

You won't regret it, he's a great guy.

As to your temp sensor, you need p/n 0005425118

Cheapest I found it is from autohausaz.com, for $12. Not bad at all. If you need anything else, buy it at the same time because you get free shipping on orders over $50.

http://catalog.autohausaz.com/autoha...uct=0005425118

Max.H

great info CWW! this is how a forum should be.