what is that clicking sound during start-up - PeachParts Mercedes-Benz Forum

blau · #1 11-22-2016, 06:16 PM

I get this clicking sound from the engine during start-up on all my Mercedes especially if I have not driven it in a while.

I don't think it is the lifters (at least I hope not.). What is the chance of having lifter problems on all 4 well maintain low mileage Mercedes. But at any rate it goes away when the engine warms up and the intensity seem to goes down as the car warms up and I don't see this problem if the car is driven a few days ago.

First if it is the lifter how can you tell it is the lifter. And if it is not the lifter is this normal and what else could this be causing the click. Many years ago from another car I was told that the ticking sound can be coming from the injectors.

Diseasel300 · #2 11-22-2016, 06:31 PM

If the car has hydraulic lifters, it's entirely possible you can get some clicking for the first few seconds after the engine starts. My SL does this as does a couple of Fords I'm forced to maintain (against my will, I assure you). The magic time seems to be >1W since last start, I'll get clicking for maybe 3-5 seconds after the engine starts. Seems to be somewhat normal for hydraulic lifters if they've sat for a while and leaked down. The lifter that "taps" is usually the one that was compressed (pushing down a valve) when the engine stopped last. It will "tap" until oil pressure builds sufficiently to pump it back up.

Lifter "tap" will make a very distinct "click" every time the valve is operated on the affected cylinder, the noise will sound like it's coming from just under the valve cover if you listen to the engine (because it *IS* just under the valve cover). If the engine is healthy, the tapping should go away after a few seconds when the engine is running.

blau · #3 11-22-2016, 06:57 PM

I agree with you that it seem to be the > 1 week magic time frame (don't have this problem when driven less than a week ago).

However, mine last more than a few seconds. The click seem to die down when the automatic idle rpm start to get lower (after a 1.5 minutes at which time the car is not at normal operating temp nor full idel rpm yet).

Also if I have not driven the car in >1 week. I usually crank the engine for 10 sec and stop and crank the engine for another 10 sec stop, another 10 sec to insure oil gets flowing before starting.

The reason I brought this up is because one of the merks the clk is particular bad. The clicking does not go away until it reach full operating temp 80 dec C. Just want to know the cause.

Here is a link from youtube (not mine) but this is what mine sound like except for me I don't need the funnel to amplify the sound. Mine sound like the funnel amplify sound the minute I open my hood !

https://www.youtube.com/watch?v=znQIiP4GCAA

Diseasel300 · #4 11-22-2016, 07:02 PM

Injectors can definitely make a ticking noise, but they shouldn't be so loud you can hear it with the hood closed. You have a Honda Accord in your signature line - Hondas have LOUD injectors, you can use that as a reference.

It's possible you have an exhaust leak on the CLK if it takes it until it reaches operating temp to quieten down. Depending on the type and location of the leak, they can manifest themselves as a "click"

97 SL320 · #5 11-23-2016, 04:07 PM

Valve tap on a seldom driven car / one that gets started - run for a few min then shut off, is common.

A lifter will bleed down if it is up against a open valve with the engine off. If you have thick oil it will take longer for the lifter to pump up.

A tap under these conditions won't cause much / any harm if you keep engine speeds below say 3,000 RPM unil the tap goes away.