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Topic: DIY - Intercooler Pump Replacement Reply to Thread
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  Topic Review (Newest First)
07-23-2012 06:52 PM
randomwalk101 I'm in search of the OEM electrical connector that connects to the stock intercooler pump. For those who did this mod and cut it off do you still have it or do you know where I can get one? Thanks.
02-03-2012 12:08 PM
jjkwak FYI very important update to intercooler pump issue on c32. I have changed my pump, but it was still not working. I drove the car without pump for about 3 to 4 years now and everything was fine, no break downs. Many years back, I took the car in to the dealer for another issue and apparently, at that time, the tech pulled my fuse and relay switch out and pushed it back into wrong slots. Thus, even with the new pump, still no go. It took 3 days to look through fuse box and diagram as well as another post and pics of other people's rear fuse box to figure out how to complete the intercooler issue on c32 models up to 2003 models. 2004 c32 apparently uses fuse in #18 instead of #5...

Open the fuse box in trunk and look for rear ebox in driver side. open up the panel and foam and on fuse #5, should be a 7.5amp fuse. check to make sure this is still good. then need to check to make sure relay next to it which is in 3rd from top position at bay C is still in the fuse box. (a correct relay switch should be black in color and have 4 prongs, in 2 + 2 perpendicular position.) Mine were empty as the MB dealer tech plugged mine back from fuse #5 into #7, and simple relay C to relay D(a white relay, not a relay switch). Relay D should be the only empty relay socket in terms of relays. If this is fully done with new pump installation, then Everything will work like magic. Remember, before doing any intercooler repair, check this step first. Even with new pump, no fuse, no relay, no go. Also, I was told by dealer that these 2 fuse/relay would normally be replaced when intercooler pump is repaired at their shop. So, maybe pick up new relay C and fuse #5. relay is about 25 bucks and fuse cheap. FYI, no one sells the relay on the internet, need to hit the dealer for this one unfortunately, so no part number is required. Oh, I called the dealer and they say that bay C is in their system as brake off switch or something like that, not intercooler relay switch. Hope this post will save a dude like me a whole lotta time and headache. Bosch SVT lightning pump works like a champ and also, no need to switch pump pipe housing either. Just get some new hose metal bolt clamps and the original hoses fit right into the new pump and no leaks. Use a large wrench and pry off old pressure clamps, and use new bolt clamps. Takes like a minute to do the pump swap.
05-10-2011 07:00 AM
No problems

Thank you for all the valuable information. My car has done 63457km and there is absolutely no problems at all. This car goes like a dream and the consumption just gets better in time.
10-11-2010 07:34 PM
2002c230 Going on 106k without pump failure. Would rather have a pump failure than my radiator failure though. My Valeo gave out and coolant started to mix with transmission. Around $600 dollars later, and a week or so of DIY work it should be good as new with a BEHR radiator installed. Full coolant, and transmission flush... Thinking about finally upgrading my heat exchanger at the same time. Along with replacement of water pump. Do both of those I'm looking around $1000 spent on the C32 in the span of several days... Not to mention around 15 hours of work.
09-14-2010 10:39 PM
2002c230 Your power loss is likely due to a bad charge air pump as you suspect.
08-31-2010 01:46 PM
Kibim Ah, good write up. I see I'll be doing this on my SLK in the near future. Had full power loss on Saturday with the car, so I'm guessing this is the issue. Also had a fairly dismal dyno test, running around 100hp short. Only 223whp. Possibly something else, or is the pump the issue here too?
08-16-2010 12:00 PM
DaytonaJae Very nice write up. This helps me out greatly, even though it is almost a year old!
I plan on replacing my defective BOSCH OE unit with a Johnson CM30. I'm sure it won't be as easy as your procedure due to the physical size difference between the Johnson and the OE pumps, but I'm sure it won't be too difficult to secure it to the OE clamp. Thanks for the info and the pics of your procedure.
09-12-2009 03:35 AM
2002c230 I'm sure the johnson pump has electrical brushes also, and eventually fails over time. Guessing it's a more reliable build though, and doesn't have nearly as high early failure rate. Not to mention it flows slightly more fluid with the cm30... There are some differences between the lightning pump, and OE c32 pump too, so the lightning might not be defective as often as the OE c32 is. By the way, after fixing the wiring harness I have not had any problems with the pump. Everything is running good!
08-29-2009 07:30 PM
Originally Posted by bokeo_2005 View Post
Nice work. I hope that wont happen to me...
if you have a bosch pump you will have a failure. its simply a matter of time
08-29-2009 07:28 PM
bokeo_2005 Nice work. I hope that wont happen to me...
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