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kayble

450 CDI oil leak diagnosis

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Hi all,

I'm a UK 2001 Fortwo CDI owner and am trying to trace an oil leak that's appearing around my intercooler and then appears to be dripping down on to the left hand side (looking from the rear of the car) transmission casing from the left/bottom intercooler body corner.

To try to find the leak, I have renewed all the jubilee clips on my turbo / intercooler hoses and made sure they are tight and used carb cleaner to make sure the area is clean for me to find the leak. I also eliminated the engine breather hose by unhooking it from the TIK and blocking the hole.

I *think* I have found the cause of the leak but would like to confirm with other owners if they have also found this leak previously. I think the leak is coming from the air temperature sensor that is inserted in to the bottom of the intercooler body that sits just above the transmission casing / driveshafts. I have a picture of the offending part:

Posted Image

That picture is actually much cleaner than the offending part of the car usually is. Typically, the sensor is caked in oil and traces of it can be seen coming down on to the transmission casing. There is a small 'O' gasket on the sensor as it is inserted in to the intercooler and I think this may have failed, allowing what oil there is in the intercooler from the engine breather to blow past the sensor and out of the intercooler.

Has anyone else seen this? I hope I'm not barking up the wrong tree - and really hoping it's not a fractured intercooler!

Thanks,

John

Edited by kayble

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That could well be - my car has the same leak (which comes and goes). Please let us know if you find a replacement O-ring that suits, as I wouldn't mind trying that out as well.Your photo is excellent and that does appear to be a low point in the system so maybe it can be used as a natural oil drain cock for the intercooler! A regular bleeding might take care of things!As far as the intercooler being fractured, even with the leak, my Scan Gauge reports manifold absolute pressures of 2.17 bar under full load (which is to say, turbo boost in the manifold of 1.17 bar, compared to 1.15 original spec), so it is not leaking any compression produced by the turbocharger. The way I look at it, if you can live with the mess from the oil leak (it shouldn't be all that bad, as the source is only re aspirated oil fumes as you know) and the intake system holds turbo compression, the intercooler ought not to need to be replaced.One thing you can to do try and minimise the leak is to maintain the oil level in the sump around 1/2 way up the dipstick - no higher - but maybe you know this already. Or is your detachment of the oil fume hole permanent? I would hesitate from blocking that hose off, as crankcase pressure could built up from compression bypassing the piston rings, which would eventually blow oil out of the engine's seals. Better then to let the oil fumes escape to the atmosphere....

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hey mike,thanks for the quick reply. Yes, I'm aware that the oil level should be on the lower side to keep residual oil vapour loss to a minimum - learned that from this forum aaages ago!When i said I had blocked a hole, I meant the TIK hose hole where the engine breather hose should be. The breather is presently free to vent to atmosphere while I diagnoses the leak, but the TIK is plumbed up.As we sppeak, I'm working up a process (with pictures) for removing the CDI intercooler - with a view to checking for perforation damage to the intercooler itself that might actually cause the leak, which is fooling me to think it's the gasket on that air temp sensor.I'll check back soon :)

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Aha, you have it all under control then. Keep up the good work!

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Thanks Bill,I had a read through - the post makes it clear that there's a wear/tear issue with the intercooler and it's plastic housing. I'll get a clearer look tomorrow but I guess I'm looking for some evident holes/ damage caused by interference between the intercooler and some plastic shrowd somewhere. I just took the car for a run and oil has once again appeared towards the lower corner of the intercooler - but above the air temp sensor which is still dry so I think that's a red herring.We shall see tomorrow (weather pending)! :)

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Ok guys,

I had good weather so I took the intercooler our for inspection today:

Step 1 Remove the back panel - detailed here. You will be left with:

Posted Image

Step 2 Remove the rear crash bar. There are six T45 bolts holding the rear crash bar and rear valance mount holes. You will be left with:

Posted Image

Step 3 Remove the TIK hose. There's a jubilee clip at the airbox and another at the turbo. Don't forget to recover the seal that goes round the turbo inlet. with the TIK removed, you'll see this:

Posted Image

Step 4 Remove the exhaust. This helps a mile with accessing the intercooler hoses. Sorry didn't remember to take a picture of the car with the exhaust off.

Step 5 Working from the top of the engine, remove the upper EGR valve intake hose:

Posted Image

Step 6 Unplug the electric intercooler fan. Next, unclip the the wiring loom section that attaches to the fan. Next, using a pair of pliers or something suitable, pinch together the two tabs in the top middle of the cooling fan assy to pull the top of the fan assy away from the intercooler. Rock the entire fan assy forward and away from the top of the intercooler and the bottom fan clips will unclip - but be gentle with it. You will be left with:

Posted Image

Step 7 Unclip the intercooler air temperature sensor connector from the bottom of the intercooler housing. Next, unclip the sensor from the connector coming from the wiring loom and set the sensor aside somewhere safe - it's fragile. The sensor is located to the lower left of the intercooler when looking from the rear of the car and looks like:

Posted Image

Step 8 Remove the lower intercooler / EGR hose. First, unclip the circlip from the bottom of the EGR valve:

Posted Image

This picture wasn't taken in series, which explains why the cooling fan is still there! Next, undo the jubilee clip on the hose at the intercooler end. Finally, manipulate the hose out of the EGR valve then off the intercooler. The part looks like this:

Posted Image

Step 9 Remove the lower intercooler / turbo inlet hose. Undo the jubilee clips at both ends and manipulate those out. This one is a royal PITA to get out by the way! It looks like this:

Posted Image

Step 10 Phew - finally we get to remove the intercooler. It is secured by four plastic clips on the top and bottom of each side of the intercooler. You need get a thin flat bladed screw driver and carefully press it in to the centre of each clip to disengage it from the plastic housing. You'll see what I mean when you get there. Disengage each clip from the sides of the intercooler and *gently* pull it forward. As with the cooling fan, pull the top of the intercooler forward and away from the rear housing first. You can then manipulate the intercooler up and out of the engine bay. Be careful not to damage the semi rigid diesel fuel return line or any of the wiring loom parts as you remove the intercooler. With intercooler out, you will see the air scoop housing as shown below - with the plastic clips that engage with the intercooler also shown:

Posted Image

That's it for the moment as I have to dash out. I've got more pictures and information concerning the nature of the oil leak from the intercooler and the vibration damage / play issues relating to the air scoop housing against the intercooler and also what I've done to hopefully stop both the leak on the current intercooler (hopefully) and prevent the air scoop assy from fouling this and any other intercooler I put in the car!

Edited by kayble

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Hope it all fits back together. Great pictures. Looking forward to more.Ian

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Fantastic series of pictures; having something like this on hand really helps to "picture" the text of this, and other, DIY threads.Can't wait to see the outcome of your intercooler inspection and the remaining pictures!MZ

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Ok guys,

More information as promised. The last post showed the method for getting the intercooler out - but what of the intercooler now that it has been removed? We'll the purpose of the exercise was to diagnose an oil leak apparently coming from the intercooler body and dripping down to the tranmission casing and driveshafts.

Other posts have detailed that the intercoolers in our cars are prone to vibration/play damage issues against the air scoop housing that the intercooler sits in. With this in mind I looked at my car intercooler a bit closer. Here's what I found, after a bit of carb cleaner was sprayed over it to clear off the oil vapour muck:

Intercooler front end (facing you as you look at it from the engine bay):

Posted Image

All looks ok on this side of the intercooler - but flip it over:

Posted Image

This is the lower left corner of the intercooler. You can see some light indentations towards the bottom of the metal assembly where the intercooler has been rubbing against the lower lip of of the intercooler/air scoop housing. There are also some more indentations slightly up the intercooler by the plastic clip that holds the intercooler on the housing.

These indentations had not yet perforated the intercooler fins - so where is the leak coming from? Ah ha! Here's a closer look of the edge of the intercooler from where the leak was emanating:

Posted Image

If you look at the intercooler, you can see that it has a top and bottom plastic piece with a metal finned assembly in the middle. The top and bottom pieces are 'crimped' tight in to the metal piece however you can see that in the above shot, the crimps are giving way and, I believe are allowing oil to seep out. Here's another close up pic:

Posted Image

The dips in the metal part of the intercooler should be tight against the relevant dips in the plastic piece to form a tight seal. This was the case for each crimp on the short edge of the intercooler at the leaking end and also half way down the long edge that was rubbing against the air scoop housing. To try and resolve this without having to buy a new intercooler I knocked the bottom lip of the intercooler on to the plastic piece and then took a large pair of pliers and pressed the metal dips back on to the plastic piece. Afterwards, the above pictured part of the intercooler looked like this:

Posted Image

You can see that metal crimps are now tightly down on the plastic lower piece of the intercooler. Also, on the longer edge of the intercooler:

Posted Image

Now - what did I do to ensure that the rubbing/ play issues wouldn't be a problem? I 'modified' the air scoop lip - by removing it! Take a look:

Posted Image

Basically, I removed the entire bottom lip of the air scoop housing to stop it from rubbing against the intercooler. I did this very simply with a pair of pliers and snapped the plastic the length of the scoop then cleaned it up with a stanley knife. I also removed the two indentations by the plastic clip that holds the intercooler in place on the air scoop.

And that's about it - I reassembled the car which is the reverse of taking it apart. I shall monitor the situation in the next few weeks and see if the leak is stopped or greatly reduced. If not, I'm probably looking at a new intercooler, or some more work to try and seal it up. For reference, the part number I took of the intercooler is: 000 2400 V005 as shown in:

Posted Image

I'll report back in a few days :)

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Brilliant stuff, kayble!Would a dose of silicone sealant once the intercooler is apart and clean have made up for any defects in the crimp seal? It would seem that actual perforation of the intercooler is not the usual failure mode, but rather a loose crimp, which would probably be impossible to prevent with a new intercooler, given enough time.I am wondering if we should see if an aftermarket intercooler firm could make up an all aluminium one for us for - perhaps - no more than the disposable piece that is OE.

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Well done, Kayble! :bowdown:

I am not much concerned with oil leaking out, so much as very bothered that the intercooler is not a sealed unit. If it leaks like this under boost, we are losing boost pressure out the holes. And with no boost, I suspect that unfiltered, very dirty air can be sucked into the manifold!

How many km on your engine, Kayble?

And do you think it would be possible to squeeze a silicone bead around the offending gaps from beneath the car, with the intercooler in situ?

Much impressed.

Bil :sun:

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Here's the thing - mine leaks and the boost is 100% normal in the manifold, in fact a little better than stock, as it always has been. Also, since this is a pressurised system, I doubt dirt would be leaking into it. That's the least of the concerns!I'm in no hurry to change my intercooler, based upon this excellent work! Thanks!

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I think you guys have all missed the whole point though:There should be NO oil passing through the intercooler!Kayble; brilliant documentation, the problem you have is the exact problem that has plagued my car for it's entire 230 000+ km life. The left half of the transmission casing gets soaked in oil, dripping down from the air sensor... all caused by the oil which is leaking out of the turbocharger's compressor side hydrofluidic bearing seal... clogging the intercooler and EGR."Sealing" the leak will only hide the problem, not solve it. :(-Iain

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In my case I would be inclined to think that even if some oil is getting past the turbo bearing seal, it's typically a minute amount and the only reason for concern is if the intercooler were to become totally clogged with oil (which, as we see, is unlikely, as it tends to leak out before it can fill). My car "uses about 0.2 L of oil over 10,000 km service intervals and probably more than half of that is combusted in the cylinders.So the real question is: in a typical cdi, what is the proportion of oil in the intercooler attributable to a leaking turbo seal, and what is the proportion attributable to the CCV system? Hard to say. If your car - like mine - is FAR under 0.05 L/1000 km of oil loss and never needs an oil top-up, my bet would be it's CCV that is contributing most of the oil to the intercooler.By the time the oil is in the intercooler, it's not going to affect the turbo at all so it is probably an aesthetic issue only (drips, messy transaxle casing), in cases where the oil loss from the engine is so minimal as to not require oil top-ups.I'm going to sit on my leak for a while yet. No point changing it, as the new intercooler will do the same thing, and so on, and so on.......

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So the real question is: in a typical cdi, what is the proportion of oil in the intercooler attributable to a leaking turbo seal, and what is the proportion attributable to the CCV system? Hard to say. If your car - like mine - is FAR under 0.05 L/1000 km of oil loss and never needs an oil top-up, my bet would be it's CCV that is contributing most of the oil to the intercooler.By the time the oil is in the intercooler, it's not going to affect the turbo at all so it is probably an aesthetic issue only (drips, messy transaxle casing), in cases where the oil loss from the engine is so minimal as to not require oil top-ups.

I agree - it's not the case that there should be absolutely NO oil in the intercooler. I think that in regularly maintained engines, the CCV system is wayyy more responsible for putting oil in to the intercooler than any wear on the turbo bearing. That is, after all, the CCV system's 'raison d'etre'. Also, the quantity of oil you typically find WITHIN the intercooler is minute and is IMHO the product of having allowed the engine to cool and the vapourised oil to condense at the bottom of the intercooler since we tend to take our cars apart when the engine is cold. Of course, what you find splattered over the transmission casing, or round your CCV breather hose as it connects to the TIK, or round the turbo inlet / outlet makes the problem look much worse than it is. but don't forget - it only takes a very small amount of oil to make an engine look like it has a bigger problem.To answer q's about silicon sealant. I think that would have been a good idea - but perhaps if you intended to take the plastic bottom of the intercooler off entirely. I think the longer term solution would definitely be to replace the intercooler with a one piece aluminium item. As for adding silicone with the intercooler in situ - I don't think you'd have the necessary access - removing it would be the best idea.By the way, if anyone fancies doing a group purchase for an intercooler, just let me know - I'm good for one :) Edited by kayble

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More information for you:The latest number for the diesel intercooler, as provided by a friendly Mercedes Smart dealer is: Q0002409V007000000.Don't quote me on this but it would seem the that the 'V007' bit of the number implies that the part has changed since my 'V005' part. It would be interesting to compare the two...

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Thanks for the great pictures and info :thumbsup_anim: That explains the damage on this intercooler......

post-35-1239711095_thumb.jpg

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yeeeeouuuch!That's obviously perforation damage caused by the lip on the intercooler air scoop housing. Mine hadn't gotten so far - which was lucky!

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Great post and excellent pictures.I can't help but wonder whether these "loose crimps" aren't a design flaw or quality control issue......I would have been tempted to take the failing intercooler to the local MB dealer for an opinion; it really shouldn't loosen up like that on its own - after all it was engineered to go into a diesel!

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ok guys,The leak is virtually eliminated. There's a slight wisp of oil on the intercooler casing but its 95% less than previously. I think if I had used silicone sealant it would have done the trick. Next time I get chance, I'll take the intercooler out and try it again. That said, if I can get a nice aluminium intercooler, that would be wayyyyyyyyyyyyy better!

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Super, thanks for the tips!We ought to get someone with a spare intercooler to get a group buy price from a manufacturer of proper intercoolers....

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Super, thanks for the tips!We ought to get someone with a spare intercooler to get a group buy price from a manufacturer of proper intercoolers....

Oh yeah - I'd be very much up for that. Not sure who to approach etc. Don't suppose anyone has a technical diagram for the intercooler with measurements etc? I can find a bunch of intercooler places on web that are based in the UK. In the absence of having a spare intercooler, I could always send over a diagram etc.

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Or maybe even have them make a metal version of the lower plenum and weld it to the core...?

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I bet that core is wafer-thin and unweldable.

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