Slow leak at radiator drain valve / petcock
Thread Starter
Super Member
Joined: Feb 2008
Posts: 699
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From: PA
09 CLK550
Slow leak at radiator drain valve / petcock
I had not driven my car in 2-3 days when I came out to see about 1/2 cup of coolant pooled under the radiator drain valve.
I made sure the red plastic drain valve was snug but I'm still seeing a small leak after every drive.
I replaced the red drain valve but its still occurring.
Behr Part Number: W0133-1640574
I did notice when I drained the system there was a small metal 'o-ring' in the pan I collected the coolant in, looks like the silver 'notched' ring here.
I put that back on the new drain valve but the leak continues.
I cannot find a part number for this ring anywhere, the one I have looks beat up.
It's only about 2oz every drive but its getting annoying.
I made sure the red plastic drain valve was snug but I'm still seeing a small leak after every drive.
I replaced the red drain valve but its still occurring.
Behr Part Number: W0133-1640574
I did notice when I drained the system there was a small metal 'o-ring' in the pan I collected the coolant in, looks like the silver 'notched' ring here.
I put that back on the new drain valve but the leak continues.
I cannot find a part number for this ring anywhere, the one I have looks beat up.
It's only about 2oz every drive but its getting annoying.
Thread Starter
Super Member
Joined: Feb 2008
Posts: 699
Likes: 44
From: PA
09 CLK550
Haven't confirmed that yet 
I plan on taking a closer look tonight. The coolant is pooling/dripping off the end of the drain valve which might just be because that's the lowest point.
I plan on taking a closer look tonight. The coolant is pooling/dripping off the end of the drain valve which might just be because that's the lowest point.
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Well, the good news is that swapping the radiator is not a major ordeal. Here's the WIS doc:
http://benzbits.com/w203/Radiator.pdf
http://benzbits.com/w203/Radiator.pdf
Thread Starter
Super Member
Joined: Feb 2008
Posts: 699
Likes: 44
From: PA
09 CLK550
Ugh that looks like a pain.
I ordered a new radiator, BEHR 203 500 39 03
In the mean while, I threw some 'Bar’s liquid aluminum cooling system / radiator stop leak' in yesterday and haven't seen another drop in about 200 miles so far.
I ordered a new radiator, BEHR 203 500 39 03
In the mean while, I threw some 'Bar’s liquid aluminum cooling system / radiator stop leak' in yesterday and haven't seen another drop in about 200 miles so far.
Last edited by ambit; Jul 12, 2018 at 09:57 PM. Reason: spel gud
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Thread Starter
Super Member
Joined: Feb 2008
Posts: 699
Likes: 44
From: PA
09 CLK550
Radiator is replaced. It sucked, I'm bleeding.
Took the bumper to get resprayed while I had it off. This is what 142,000miles looks like. Poor thing
New rad is about 1/4" thinner than the old one.
No obvious damage in the area that was leaking
Back together
And I'm pretty sure I found the leak from my windshield washer fluid!
Took the bumper to get resprayed while I had it off. This is what 142,000miles looks like. Poor thing
New rad is about 1/4" thinner than the old one.
No obvious damage in the area that was leaking
Back together
And I'm pretty sure I found the leak from my windshield washer fluid!
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Good job! But you should not have needed to remove the bumper - that step was only indicated for the C32 AMG (203.065). Of course if you needed it painted, and that made the job easier, I understand that. I have the one on the CLK550 totally taken down and primed, painted and clear-coated. The rock chips were starting to shatter the clear coat and it was peeling. Looked like it had leprosy!
Thread Starter
Super Member
Joined: Feb 2008
Posts: 699
Likes: 44
From: PA
09 CLK550
Ehh removing the bumper isn't a big deal 
I think I've had about enough of this car. I'm going to look at a 2009 CLK550 on Friday, 1/3 the miles of mine. So respraying the bumper just incase I decide to sell it.
Removing the bumper did make the passenger-side lower coolant and trans line much more accessible, and I was able to loosen and pull the hood latches/headlight mounting out of the way pretty easy.
And with the bumper gone I was able to get to the bottom of the washer fluid container and find the leak. It was on the backside of the reservoir in pic #2. Looks like the pump for the headlight washers (that I've never ever used) went through some freeze cycles and exploded. New one on the way for $20.
I think I've had about enough of this car. I'm going to look at a 2009 CLK550 on Friday, 1/3 the miles of mine. So respraying the bumper just incase I decide to sell it.
Removing the bumper did make the passenger-side lower coolant and trans line much more accessible, and I was able to loosen and pull the hood latches/headlight mounting out of the way pretty easy.
And with the bumper gone I was able to get to the bottom of the washer fluid container and find the leak. It was on the backside of the reservoir in pic #2. Looks like the pump for the headlight washers (that I've never ever used) went through some freeze cycles and exploded. New one on the way for $20.
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I really loved my MY2007 CLK550. I did endure a bunch of problems, but overall, the car was a lot of fun. Mine experienced the "balance shaft" failure (actually just an idler sprocket on the V8), but the repair was covered under warranty. Unfortunately, the dealer did a poor job and damaged the flywheel when re-installing the engine. I think you will like it. The interior will be the same as your CLK55, but the engine has more power and the 7-speed transmission helps with perofrmance and economy.
Last edited by Rudeney; Jul 19, 2018 at 10:50 AM. Reason: Correct info
MBworld Guru
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The real problem is not with balance shaft itself, but the timing chain idler sprocket forged onto the front end of it. It does double duty by rotating the balance shaft and acting as an idler for the timing chain in the "V" of the engine. The V8 doesn't have a balance shaft (no need - it's inherently balanced), but it still needs the idler sprocket. So, it;s a simple "gear" bolted to the front of the block. And the same manufacturing defect that makes the V' balance shaft sprocket wear prematurely can make the V8's idler sprocket wear. Here's the TSB which included the range of potentially affected engine serial numbers:
http://benzbits.com/BalanceShaftTSB.pdf
But if you;re looking at a MY2009, there's no worries. The balance shaft and idler sprocket problem was discovered and corrected about halfway through the MY20007 build. So, any MY2008's or later are fine.
http://benzbits.com/BalanceShaftTSB.pdf
But if you;re looking at a MY2009, there's no worries. The balance shaft and idler sprocket problem was discovered and corrected about halfway through the MY20007 build. So, any MY2008's or later are fine.
