1320pilot

I have a 2003 SL55 well taken car with only 58000 miles on it.
On several occasions I have opened it up to see what it has only to be disappointed at what feels like a limiter stopping me at 110 mph. The car pulls very hard right up to that point the just stops . I am impressed with the power and torque it has up till that but I know it should go at least 150's mph and plan to get it to over the 200 mark, but first this hurdle. Thought and or fixes?. I have no intentions of going to the Stealership at all.

carguyshu

afterwards if you slow down then get right back on it does it still have power? If it doesn't, then I would look toward the intercooler pump. If that is weak then the air intake charge will get hot and the supercharger will get turned off resulting in almost no power.

I've never heard of an SL55 not being either 155 or 186 limited. Cars are suppose to be limited to whatever the original tire max speed rating was on the car.

cnterline

Intercooler pump is a common failure on this car,and will cause that symptom,start there

sound 8

Sorry to disagree but it wouldn't just stop at 110 mph with a mechanical
problem, it has got to be electrical. Can you set the ecu to a max speed,
maybe someone has at 110.
S8

1320pilot

Thank you carguyshu and centerline.
I will try your suggestion about slowing down then right back into it to see if there is still power. Lots of rain here so will be next week before I can try it.


Is the pump difficult to replace? I pretty good with a wrench as my name might imply. Is there another diagnostic procedure I should look at? I do not have a star program as of yet and as of my first and last fleecing at the stealership I wont go back there. I just replaced the supercharger bearing two weeks ago and thought that might correct it. Anyone have a DIY on the pump replacement?

1320pilot

Sound 8 where would I look for an electrical issue?

shardul

iTrader: (1)

pump is located behind the passenger side fog light. remove the 2 clamp and the bracket and swap the pump. The system will self bleed so you may have to keep adding water / coolant over a day or two.

sound 8

Check with MB if there is a facility to set your top speed, I am sure cars
have it.
S8.

1320pilot

Thanks Shardul you sound pretty knowledgeable. would you know of any electrical issue like the above person Sound 8 suggested? it feels like I hit a rev limiter when I get there?

sound 8

You say it gets to 110 and just stops, believe me it is not the intercooler
pump. I don't know of anything mechanical ( apart from an iron bar through
the wheels ) that will suddenly stop you at 110. If it was rev limiter the car
engine would be screaming in third gear, is it stuck in gear ?
To stop you at 110 it must be a limiter of some kind, and there are plenty
of them.

sound 8

You say the car pulls very hard with lots of torque then stops at 110, with
that power the pump is working well.

cnterline

To the OP , if your intercooler pump is bad ,your intercooler will heat up real quick and cause your intake air temp to go up real quick ,at a certain intake air temp the ECU will in turn shut off your supercharger ,now you have an sl500,which would make your car feel like it does,no power at that speed.,like I said start there,these stock pumps were notorious for going bad .this is why you should test it ,if you get on it and it pulls good once and lays down,immediately try again if not the same pull this will confirm it's not working,if you unplugged a good pump and made a pass it would pull hard till ECU turns off supercharger,
If you do replace it.,see if you can get two hose clamps ,the pliers type that squeeze the hose so no mess

sound 8

Hi I agree a intercooler pump affects the performance, I also know that
you need to get temperature high enough for it to start having an affect.
The op says it cuts at 110, well he would have to drive it hard first before
it would have an affect. He say the problem is it stops at 110, if he drives
off his drive before the engine reaches any sort of temperature he says
it pulls hard but still stops at 110. I have had the I/C pump replaced on every car I have owned, some of them felt like the supercharger/turbo
stopped working, but they still kept accelerating, just down on power.
With it stopping at 110 it must be electrical.
S8.

sound 8

Please read..it feels like a limiter....the car pulls very hard ..right up to 110.
I am impressed with the power and the torque it has..
Come on, does that sound like an I/c pump, why would the pump stop it
exactly at 110 every time.

cnterline

200 hundred deg iat,reduced timing ,0 boost might hold a car back a tad
Just sayin,is that definitely the problem ,who knows,that's what I feel it is ,from my own experience of my car falling flat on its face at the track at 113 mph

Nosmo SL55

OK, long shot here, but worth checking anyway.

On your cruise control lever/stalk make sure that the green led light half way down the stalk isn't on (when the car is running).

A speed limiting function is activated by pushing this stalk in towards the steering column (green light on). Push it in again to reset (green light off).

It could possibly have been pushed in on a previous occasion at 110mph and is set at that speed.

I say long shot because I would have thought that it resets itself automatically when the car is turned off?

cal1

Put me in the I/C pump camp. It would be a good idea to replace it anyway with the newer bosch pump. WOT at 110, you should be at the "hoooollllllyyyy ssssshhhh-t" point, not "hey where did the power go?"

fxrs1955

While it's a good idea to replace the pump and I would replace it I'm in the electrical camp. In any case I'll be curious as to the cause.

CHADisBAD

like cnterline and others said... most likely the IC pump. start there, wouldn't hurt to replace that either way.

sound 8

OK change the I/c pump, and when you find it still stops at 110 you will need
to look at something electrical, perhaps your cruise control is faulty.
S8.

blackbenzz

Pop in an IC pump and see what happens. It's a worthwhile upgrade regradless. Relatively inexpensive too.

cnterline

I have a trunk tank,and my ic pumps have manual switches to operate on off for when I have key forward for scanning or other things so I don't drain the battery ,so at Atco raceway I accidentally left them off on first run ,car ran an 11:07@113 falling on its face crossing the line ,for a comparison next run after it cooled down from an over 200 deg F IAT 10.80@130 plus almost 3 tenths plus 17 mph ,so IMO and firsthand experience of NO intercooler pump ,I feel that is your problem ,or part of it .

sound 8

You may feel a difference in power, but did your car stop accelerating,
I don't think so !

cnterline

Ingenere

If the car accelerated hard and then hits a brick wall, its not the IC. It is a limiter in the ECU. If I remember right, there may be a limiter that one can program in the car. It is either an alarm or a limiter. I'll have to check my car.

We've been doing ECU tuning on these cars since '03, and I've never seen a bad IC pump cause it to hit a wall. Of course, I could be wrong.

As far as the IC pumps go, the originals were a weak link. The latest versions are reliable, at least in my car, as well as customer cars. They are an easy change. Someone said behind the fog light, which is true. However, the easiest way to get to it is through the passenger side wheel well.