Assessing Hydraulic Lifters

[JHZR2]

My 91 300D has a tap at fast idle. It runs beautifully smooth and strong. When I bought it the PO said that a diesel shop said it may need a lifter. I don’t know that it’s true, but they are known to go bad on these engines after high mileage.

I pulled injectors for refurbishment, and needed to replace a glow plug and VC gasket, so now is the time to check them.

Engine looks clean and cam looks great. Not sure if the brown coloration in some of the photos is because of my brown garage roof, or something else.

So, what’s best practice for checking out lifters? My understanding for these is to turn the engine by hand until the cam is facing directly away from the lifter, and then use a plastic pressing tool of some sort (non-marking). If the lifters move, they’re bad and leaky… if they stay solid and firm then they’re good.

Is it as simple as that??

Thanks!

 

[Trav]

These use a spring and ball valve to prevent bleed down, ideally pressing it down should tell you if it is holding oil, but if more than one has bled down which can happen if the lobe stopped in the compressed state it may be difficult to isolate the individual. I use a mechanics stethascope on the cover with the engine at operating temp to at least isolate the cylinder then remove them. I usually just replace them.

 

[JHZR2]

These use a spring and ball valve to prevent bleed down, ideally pressing it down should tell you if it is holding oil, but if more than one has bled down which can happen if the lobe stopped in the compressed state it may be difficult to isolate the individual. I use a mechanics stethascope on the cover with the engine at operating temp to at least isolate the cylinder then remove them. I usually just replace them.

Ok so I’m thinking then that I need to note position of each, and any that have the lifter compressed, if they don’t test as functional, I’ll mark as suspect but need to retest.

A good test is a good test, but a suspect unit with a lobe that was downward is not guaranteed to be failed.

Thanks for the insight!

 

[Chris142]

Look at the width of that timing chain!

 

[spasm3]

The cam lobes look perfect!

Beware the sand/dirt that fell onto the cam lobes from taking the cover off. I see it in a few pics.

 

[Cdn17Sport6MT]

Look at the width of that timing chain!

My '85 Moto Guzzi 850 cc motorcycle uses a duplex chain, too... In fact the '86-'91 Mercedes V8 4.2, 5.6 litre V8 chains are direct fits. Gotta hand it to engine designers who fit duplex chains .

 

[JHZR2]

The cam lobes look perfect!

Beware the sand/dirt that fell onto the cam lobes from taking the cover off. I see it in a few pics.

Yeah I’m not sure what it is. It isn’t sand. It’s not hard. Regardless I don’t like it!!

 

[JHZR2]

Look at the width of that timing chain!

The cam lobes look perfect!

That’s why this car is ready for another 228k… or when rust consumes it.

 

[JHZR2]

Finally found time to mess around some more. Turned the engine over by hand, checked all lifters, most twice. I used a soft plastic tool as there was a YouTube video where the tech used that sort of trim removal tool.

None of the lifters budged with this tool or a wood handle from a small brass brush. So I think I’m good. Injectors will go in tonight or tomorrow, I suspect that some of the tapping is from that.

I did notice some strange wear/color patterns on the cam lobes - only visible, nothing to feel. Cam overall seems great.

Got a new valve cover gasket installed, new idler pulley, cleaned the pullies, now just need a new working water pump.

 

[JHZR2]

So I wanted to follow up on this again.

This was the car that I had the prechamber replacement on. Since then, I rebuilt, pop tested and balanced the injectors, fixed the prechamber, drove it to high performance lubricants (IL) and back, then parked it a while as I rotate my vehicles. I’ve been driving it recently, and yesterday and today it seemed like the tap was more pronounced.

It hasn’t used a drop of oil since I did the oil change 3000 miles ago. That was mostly high speed driving to IL and k.

I checked the timing chain stretch, it’s only 2 degrees.

I checked the lifters per earlier in this thread.

The car drives smooth and nice. It’s great on the highway. A little stinky in town (I think there may be a slight exhaust leak somewhere).

But that tap.

Last night:



Today after I drove home from work I listened with a stethescope. It seems like it might be at cylinder 1/2, or injector 1/2. This is just from listening to each one, each line, the valve cover, etc.

But I did the test on them, just like shown at 3:00 on this video:



And mine didn’t move at all. Any one. Certainly not with the kind of motion like is shown in that video.

Sounds almost exactly like this at 15 seconds. Granted it’s a Mercedes gas engine, but same era and perhaps similar cams and lifters:



I’m kind of tempted to see if I can try a chemical fix just to get the proof of concept. If I can get a temporary relief, then I’ll know it’s the lifter. I do have HPL cleaner, I don’t think a thinner oil or ATF is the right move. I do also have Schaefer’s 132 which is super thick.

Or I can do something else. I just can’t pinpoint it wel enough by listening with a stethoscope to make heads and tails of the situation. And every injector is kind of noisy anyway.

Any thoughts on how to proceed?

 

[Majsmith]

So I wanted to follow up on this again.

This was the car that I had the prechamber replacement on. Since then, I rebuilt, pop tested and balanced the injectors, fixed the prechamber, drove it to high performance lubricants (IL) and back, then parked it a while as I rotate my vehicles. I’ve been driving it recently, and yesterday and today it seemed like the tap was more pronounced.

It hasn’t used a drop of oil since I did the oil change 3000 miles ago. That was mostly high speed driving to IL and k.

I checked the timing chain stretch, it’s only 2 degrees.

I checked the lifters per earlier in this thread.

The car drives smooth and nice. It’s great on the highway. A little stinky in town (I think there may be a slight exhaust leak somewhere).

But that tap.

Last night:



Today after I drove home from work I listened with a stethescope. It seems like it might be at cylinder 1/2, or injector 1/2. This is just from listening to each one, each line, the valve cover, etc.

But I did the test on them, just like shown at 3:00 on this video:



And mine didn’t move at all. Any one. Certainly not with the kind of motion like is shown in that video.

Sounds almost exactly like this at 15 seconds. Granted it’s a Mercedes gas engine, but same era and perhaps similar cams and lifters:



I’m kind of tempted to see if I can try a chemical fix just to get the proof of concept. If I can get a temporary relief, then I’ll know it’s the lifter. I do have HPL cleaner, I don’t think a thinner oil or ATF is the right move. I do also have Schaefer’s 132 which is super thick.

Or I can do something else. I just can’t pinpoint it wel enough by listening with a stethoscope to make heads and tails of the situation. And every injector is kind of noisy anyway.

Any thoughts on how to proceed?

Turn up the radio !

 

[JHZR2]

Turn up the radio !

It goes away completely when on the highway.

Cam seems no worse for wear. Just don’t like the sound.