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1999 C280
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56 Posts
Discussion Starter #1
Hi guys,
I am planning to replace the following in my 99 c280 with 70K miles -
1) Valve Cover gaskets
2) Intake Manifold gaskets
3) Ignition Coils
4) Spark plugs
Is there anything else that I should check for when I do the above or keep any replacement parts handy in case any part that could likely have gone bad or brittle? Not to make the question vague, I was thinking of breather pipes, or any other parts someone may perhaps recommend from experience? I got to know about the breather pipes here -
This is my only car and my aim is to keep the down time to the minimum possible.
Thank you very much in advance!
 

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1999 C280, 2000 C280, 2000 C230K,2011 C300
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668 Posts
Unless 1 and 2 are leaking, I might leave those alone.

If car is running fine then coils are fine. Those are $50 each and you need 6!

Plugs sound great and change the wires because you may mangle some. Get the special offset wrench that helps get the old wires off.
 

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1999 C280
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56 Posts
Discussion Starter #3
Hi glenmore, good to hear from you buddy!

Re 1 and 2 leaks -
Pls see pics 1, 2 and 3 of the cylinder head (valve cover). ds looks dirty but dry. ps is all oily under the MAF duct if you zoom in on the pics and strangely nothing is oily below the valve cover - just up on the valve cover itself and the inner two coils partially under the MAF duct.
What do you think? Should I just wipe the ps and see if it gets oily again?

Also unrelated to leaks in this area pls see pics 4 and 5 of the plastic panel below the oil pan. Hadn't seen it this oily before oil change last year on July 06, 2019. I used all OE for the oil change down to the copper ring washer by Fischer Plath and it was done under my observation. Could any other oil get there besides the engine oil?

Re Coils, Wires and Spark Plugs -
My car is vibrating bad at startup and at stop, takes time to get to speed from stop. Is there a way to find out what is doing it - a coil/s, plug/s or wire/s? Is there a way to test each?
BTW, what wires did you replace with - Bosch OE is 2K ohms and Bremi and others are 1K - any real relevance?
Sounds like you recommend only replace any bad coil rather than the entire set but replace the wire set?

Thanks for any help and stay safe :)
 

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Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG
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4,272 Posts
Both valve covers gasket
All breather hoses
All vacuum lines (do not touch the vacuum line that goes to the intake manifold runner solenoid!!!! That one is not replaceable!)
Both motor mounts
Transmission mount
 

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1999 C280
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56 Posts
Discussion Starter #5
Hi Deplore, good to hear from you too!
So just valve cover gaskets, and not the intake manifold gaskets?
Replaced MMs and TransM last year with help from you and others here - RR Engine Mounts - 99 C280
to be clear - is your response above for solving problem I described with pics or recommending additional work to my OP?
I'll figure out which are the vacuum lines and which one not to touch!
Thanks buddy! Stay safe :)
 

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1999 C280
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56 Posts
Discussion Starter #6
oh glenmore and Deplore,
just remembered about 2 months ago when car started limping and shaking, OBD read error of something like P03...i forget the complete err code but it was bad something on one of the cylinders. That's sloppy on my part, I will test again and post. CEL is still on. So although I decided to replace all the plugs, wires and coils in the first place, I always at least want to know the bad part.
 

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Outstanding Contributor , SDS Guru
1998 MB E300TD, 1997 MB E36 AMG, 2001 MB E55 AMG
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4,272 Posts
My car is vibrating bad at startup and at stop,
That's what I was using as a basis for motor mounts, but seeing that you've already done it last year, then it's likely not that.

takes time to get to speed from stop. Is there a way to find out what is doing it - a coil/s, plug/s or wire/s? Is there a way to test each?
Usually the coils, read the codes, and then unplug the offending coil, unplug a known good coil that's easy to get to (cylinder 1, maybe) and then swap. Put bad coil on cylinder 1, known good coil in the original cylinder with misfire.

Clear code and start the car. If coil is bad, the misfire will follow the cylinder. If the spark plugs or the wires are bad, the misfire will remain at that same cylinder.
 

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1999 C280, 2000 C280, 2000 C230K,2011 C300
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668 Posts
Yes, DS looks good. I would clean PS, and carefully around MAF. Make sure air filter and inside air pathway to MAF sensor and throttle body is clean. Maybe oil is getting in there and fouling MAF? For the meanwhile wipe and monitor.

Does seem like a lot of oil on the splash pan but you might just live with it for the meanwhile. My cars leak and I've done the oil pans maybe twice now but haven't been able to do the job correctly. Not hard, just difficult to execute well. No gasket here, you use the black sealant, and the trick is to hold the pan in place with one hand and start enough screws to hold it in place without squishing the sealant all over the place. (I've thought about this and I think what I'll try next time is to jam some wood dowels into some of the screw holes and use them as locator pins to keep the pan centered while I get some of the screws started.) Again clean the pan area well and try and find out where it is coming from.

A common leak is the rubber washer at the power steering reservoir but you'd notice missing PS fluid.

Rough idle in gear and smooth idle in neutral is typically motor mounts but you have done those. Could be crap parts though and you have to do them again.

A look see at the plugs might tell you something. And they are relatively cheap to replace.

Try and get some codes and you might be able to narrow it down, could be MAF, could be O2 sensors or just a vac leak.
 
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