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Discussion Starter · #1 · (Edited)
Hello..my first post here!

I have a 1998 slk 230. 62,000 miles. 60k service was done around 58k..and there were no problems at that time (fuel pump was replaced, spark plugs, etc). I now have a few problems all happening more or less simultaneously.

First, I got a P0401 error (secondary air injection malfunction). Looking on the forums here, I see the most likely cause is faulty air injection valve. Symptons are rough start when it's cold - and also occasionaly will idle roughly. Usually it will run fine after 10-15 seconds. If I turn it off and start it again right away, usually it will run perfectly the second time.

I was going to replace that, but also notice I've been losing coolant. I couldn't see where it was leaking - so I had a mechanic check the coolant system under pressure. There is no pressure loss (no leaks detected) yet I've had to add some water every few days lately.

I put 2+2 together and was looking at my exhaust. It's blowing white smoke, smells of coolant and is dripping water!

So..that tells me: blown head gasket, right?

Hold on..one more sympton: I notice oil leaking around the camshaft position sensor (magnetic sensor). This could also explain the rough starts and rough idle I believe, right? Could this also be the cause of coolant getting into exhaust? Or does that necessarily mean a blown head gasket?

The other day after I started up the car..the usual rough idle that normally goes away in a few seconds, lasted a little longer than normal so I gave it some gas (pressed gas pedal) and it backfired...and then immediately registered a misfire in cylinders 1 and 4 (if i remember the number correctly).

So..I ordered the air injection check valve before I realized the whole coolant issue..so it's on its way...any help in putting all this together?

thanks
 

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1998 SLK 230, 2016 Tesla Model S P90D, 1984 Alfa Spider Veloce, 2008 E320 Bluetec (former)
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Either way, it can't hurt to replace the valve, as it will eventually go. Replace the valve, clean the maf and the throttle body, and then go from there. You also might have a small crack in the coolant hose that runs in that area near the duo valve (thing with the two 1-inch diameter cylinders near battery). Mine wore out there and lost all coolant.
 

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Golf R32 / Prev R170 SLK
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Sadly this series of engines, esp in other markets, do get head gasket failures. A write up in in one of the links in my sig.
No water probs near front cam electro magnet.
If it leaking oil it will either be where it seats, (remove clean, wipe sealnt sparingly on face and refit)
or thru the magnetic coil and out the plug (new electro mag needed. (check for oil ingress up loom. It can get to main ECM and cause probs. If that is the case, discon neg bat, remove ecm, wash clean with cct board cleaner, try to wash out loom, normally needs replacing but)
 

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Discussion Starter · #4 ·
Thanks guys..I was also wondering if there is any way that if the cam sensor is not working - if that could affect the timing in somewhat that coolant could be getting into the exhaust that way - as opposed to because of a head gasket leak. I can't think of how - but was just doing wishful thinking.

If there really is coolant in the exhaust, must it be either because of cracked head or leaky head gasket?

One other question: a mechanic I know suggested that it seems like a small leak in the head gasket and that maybe putting a head gasket sealant in the coolant might fix it and avoid having the cost of replacing head gasket. Any thoughts about that?

thanks again
 

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Thanks guys..I was also wondering if there is any way that if the cam sensor is not working - if that could affect the timing in somewhat that coolant could be getting into the exhaust that way - as opposed to because of a head gasket leak. I can't think of how - but was just doing wishful thinking.

If there really is coolant in the exhaust, must it be either because of cracked head or leaky head gasket?

One other question: a mechanic I know suggested that it seems like a small leak in the head gasket and that maybe putting a head gasket sealant in the coolant might fix it and avoid having the cost of replacing head gasket. Any thoughts about that?

thanks again

Wishful thinking sadly.

Some sealers seems to work. Dont use a rad type sealer use one esp designed to react with engine gasses IF you want to try it.
 

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Leaky head gasket

Just found this post since i now have a similar issue with my 98 slk 230 about 82k on it and the low coolant light pops on once a month. No signs of leaks anywhere and pressure test showed nothing. I don't think it to bad yet but the mechanic i bring the car to said he finally saw some evaporation coming from the first head when changing the plugs and coils and is certain now that's where I'm losing coolant. I wanted to have this taken care of before the leak gets worse but the mechanic says to wait it out and didn't even want to give me a price but said it would be pricey. He also mentioned to use a Head Gasket Repair as suggested above. Is there a brand that anyone has had success with and am i at the stage that i should now try and use it? Also what would a proper repair cost to fix this issue be since i really would like to know what I'm dealing with. Thanks for the help :)
 
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