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Old 10-04-2019, 05:01 PM   #1
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coolant leak? normal?

My 2017 4x4 sprinter seems to consume coolant. Maybe a liter or more over 20K miles. I was told by a random mechanic that this should not happen - if coolant is reducing, it means there's a leak somewhere. Mercedes dealer tells me they did a pressure test and found no leak. Yet the shrinkage continues.

Is this normal?

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Old 10-04-2019, 09:42 PM   #2
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Isn't a pressure test normally done by removing the "radiator" cap and installing a pressurizable cap in it's place? If that's the case, you existing cap isn't part of the pressure test and may be the problem.


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Old 10-05-2019, 12:43 PM   #3
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The mechanic who said a reduction in coolant is not normal is 100% correct.

Anyone who owns and/or uses a cooling system tester typically knows and has the adapters to check both the system and the cap as well. Even as a drive way DIY my Stant set-up can test any E-Series cap.
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Old 10-06-2019, 12:37 AM   #4
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Yup, nothing normal about coolant consumption. It's possible it only leaks when hot,so pressure testing after cooling off may not be totally accurate, but you should't be losing coolant.
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Old 10-06-2019, 09:45 AM   #5
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A liter in a full size van is only very small percentage of the total volume. I'd top it off with some distilled water, mark the reservoir, and see if it drops any further. If this was the first 20k miles, it might be normal. Every new car I've had seemed to "lose" a pint or two in the first 30,000 miles. I suspect it's a combination of trapped bubbles eventually working out of the system, and possibly some expansion in the all the rubber and plastic components.

If it continues... that's not normal. But in a diesel it can be VERY hard to track down the leak, because it may only happen at high operating temps, which is something you can't replicate in a shop. Sometimes you have to just let it get worse to have any chance of tracking it down.
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Old 10-14-2019, 04:32 PM   #6
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Thanks all.

Good to know that some early reduction is normal, but also that more is not. I refilled to the line on the tank at 18K or so, and it's continued to go down visibly.

Any thoughts on how best to press Mercedes on this? They were willing to look, but as I noted were also dismissive.
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Old 10-14-2019, 06:59 PM   #7
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I'd annoy them enough to have it recorded and documented in their records that you brought it in with said problem just in case it really manifests itself in some way outside of warranty.
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Old 10-15-2019, 07:25 AM   #8
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X2 on documentation. Mark lines and dates on the bottle, and when you drop it off, make it clear you aren't leaving without paperwork at last. Once you hit 3 visits, you can send MBUSA a last-chance letter, and initiate a lemon claim.

I had to do the last-chance letter on a Ford Fiesta for a nuisance check-engine light (no other symptoms). Root cause was dealer incompetence, as they tried throwing part after part at it to no avail. Finally Ford sent out an engineer from Detroit, and found the PVC hose had been kinked at some point slightly restricting flow. Just enough for the computer to detect it. If the dealer had followed Ford's diagnostics procedure, they would have found it the first visit. Ford ended up sending us a very nice check for the hassle.
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Old 10-15-2019, 09:42 AM   #9
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If your Sprinter has an EGR cooler with coolant lines going into it,I would have that cooler checked. possibly with inspection camera. I have seen issue with leaking EGR cooler on "other" German made vehicles. Just my 2 cents.
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Old 10-16-2019, 01:10 PM   #10
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A quick search on sprinter forum turned this up. Different model but interesting way to diagnose a leak...

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