1. IC pump was replaced recently; all is well
2. Learned here, that the pump continues to spin after engine shut-down
3. Checked front right; humming pump for about 5 seconds
4. did not hear the pump - after driving hard
5. Test as follows:
a) engine running from cold-start for about 2 min. - pump is spinning
b) I repeated this about 5 times until engine temp. reached about 90 degrees; the pump was spinning ok - but, the hotter the engine got between the tests, the shorter the time it took, until the pump would shut down (not enough time to rush from the door to the front, less than 2 seconds!). Car is running great.

Does anyone know, where the thermo-switch for the IC pump is located? The 5 seconds or less is determined by coolant temp. There is nothing inside the pump to shut it off after the 5 sec. spin while it's emptying the IC.

Any thoughts?

 

IC pump does not fail at once. Before it is completely dead, it come on and off intermittently. There is no thermal switch, DME turns it on.

Just get it replaced, do not waste your time.

 

Thanks Vadim; here is a follow up, actually 2.

TESTS I just conducted: (the SC is not engaged at idle)

Engine ON Engine Temp. IC Pump runtime after Engine shut-off
(idle)
30 seconds cold start 35 seconds
1 min. 50 25
1 55 20
1 65 18
3 80 10
3 85 5
3 about 88 2 or less!!

Question: What triggers the pump duration? I doubt it has anything to do with the condition of the pump (assuming it's functional/mine is).

Vadime; What is the DME you mention? (Distributed Management Environment)?

If it is, it still needs a "physical" trigger to control the spin duration of the IC pump (see my test numbers above, dependent on coolant temp? IC temp? or what). If I am right with my assumption.... IC pumps may have been replaced because one doesn't here them?? (the less tech. folks?). Bummer.

How does the temp. reading get to the DME (from where?) - via the IC temp. sensor? In reality - everything is running fine in my case (the pump is less then 500 miles young, car has no mods; 60K miles). But I've monitored this spinning thing now very closely (thanks to the Forum) - the pump is fine (absolutely no SC cutouts starting in 1st to redline/shift into 2nd - runs to redline; shift into 3rd.../runs supurb! - tried it over and over - very consistent = ok).

Actually it doesn't matter (to me), how long the pump keeps spinning after shutdown; but I don't understand this one (reversed logic). I would expect the pump to keep RUNNING/spinning when the coolant is HOTTEST = circulating fluid through the IC, while it's cooling off.

Please tell me where I'm heading down the wrong path.

 

DME is German for ECU.

On later C32s the pump will come on only when kompressor clutch is engaged.

I would recommend to simply run a wire from any "ignition on" accessory to the pump, so it runs whenever the key is turned on. This is what I have on my C32.

 

Thanks Vadim;
Yes, that will take away the 2002 uncertainty - "what turns the pump on/off" when...; since there seems to be no error code for a "nonfunctioning" pump, apparently the ECU is blind to notice this radical but practical solution. Good suggestion, thanks.

Just one follow up. Any idea what the possible temperature BUILDUP will be, when the car is shut down; therefore the pump shuts down momentarily, coolant is stagnent in the IC and quickly starts heating up above 255F... is it going above 312 and may become a superheated steam situation - can there be a BOILING POINT/pressure buildup (?) which may harm the IC? Is there a checkvalve in the cooling system (engine water pump area >>>> coolant is trapped in one direction?). Just thinking "Why did Vadim do this....?"; answer if you feel like it. Thanks

 

There is nor check valve in the system. I doubt the temps will go above 300F, unless you are in Death Valley.

Like I said before, just separate the system from the engine cooling system and wire up the pump on key-on fuse and you will not have any more worries.

 

Thanks Vadim

 

Uweb, I had my pump replaced by the dealer under warranty about 1,000 miles ago and notice the same thing. Go to pull the car out on the driveway to wash it and the pump runs for a minute when the car is cold??

When its warm, it does not run as much, sometimes you can't even tell if it is running? It doesn't seem right as one would think when the car is at its hottest that you would want more circulation of the coolant. I wonder if the dealer had done something with it to reduce the "on" time since these pumps just don't seem to last that long?

Vadim, how many hours do you have on your pump with your hard wiring and what accessory did you tap into in order to run the pump all the time?

EDIT:
After reading back through this post and Vadim's reply is it possible that if you had you pump replaced by the dealer, that they reflashed the ECU to only engage the recharge pump in conjunction with the supercharger engaged????

 

I have an original pump in my early 2002 C32, and the car has never been to a dealer in it's life. My pump does exactly the same, runs longer when cold.

 

I would also like to wire up my IC pump to run wiring it throught the fuse box as Vadim sugested. Would a relay be required, or just a wire with a 15amp ? fuse inline with it ?

 

Thanks guys;
The Vadim solution makes sense, but I also belief, he has the pump coolant "re-routed"; this is painting a slightly different picture.

Two thoughts:
1. The C32 Firmware/SW engineer ("I is one") goofed (he applied reversed logic... is easily possible/"outsourcing...." haha/ example: my Sony laptop tells me, "your Battery needs re-charging" when it's at 100% and it says "Battery is full/when it's near empty"....). As a result of such a reversed SW switch, the pump may run as described above.

2. The need to run the pump after engine shutdown may have more sinificance then we "guess" - the 312 F actually could become an issue, releasing pressure through an IC crack - if it gets that high. The safety valve/cap goes off at 1.4 Bar (?) what does that translate to?

Vadim, Death Valley? Almost right. It's AZ for US - but DV for about 200 a year sneaking in..different subject.

 

I doubt that there is anywhere in the I/C loop that gets that hot. The "hot" spot is the actual intercooler and even that has to be relatively cool compared to a portion of the engine block.

 

Fifth Ring;

That's the point; when the IC temp.gets to 255F the SC cutoff sets in; but the temp. keeps RISING to engine/coolant temp. level!! The question is, how much will it rise - remember, this is an ABNORMAL condition, it NEVER should reach 255F in the first place. Mercedes KNOWS, but may not want to release the data.

We know, the electric FAN will continue to run in 100F plus outside temperatures - but only for a short time; suggesting, that the IC coolant will/should benefit from that - while the fan spins - and the IC pump is on. May be one could fabricate a tie-in to the fan (IC pump shutoff only; but the IC pump ON control preferably via the SC/electric. clutch). I think that would be my first choice - w/o having to add a totally separate coolant system JUST FOR THE IC).

CONCLUSION:

It would be risky to "hot-wire" the IC pump (in older C32s); Vadim indicates, the new models apparently sync the IC pump ON/OFF with SC = ON/OFF - that makes sense. This may be a better "rewire". How the ECU update will help/mess things up - dunno. Any thoughts?

Anyone replace their IC with a different more solid unit? At what cost/parts and labor.

 

What do you mean hot wire it in older C32s? The 2002s already run the IC pump the whole time the car is on. If you have an 03-04, you should add a relay to always have the pump running while the car is on. I did this mod and there was a noticeable difference in heat soak. The only disadvantage to this is that the flakey pump will wear out even quicker, but that's not really a problem.

Having the IC pump running the whole time helps regardless of whether the IC coolant is isolated.

 

No, once the kompressor is turned off, IAT goes down to 170F fairly quickly and kompressor gets turned on again, only to shut-off at 255F again.

Short of going with SLR style IC, there is no easy solution.