I think the head gasket blew on my 350SDL - PeachParts Mercedes-Benz Forum

compu_85 · #1 06-28-2023, 08:59 PM

Going to dinner I had top stop to let the dog go for a walk. Earlier in the week I notice a lifter had started to tick... it had stopped ticking when I left home but now it had turned into 2 or 3 ticking quite badly.

Additionally, the oil pressure gauge was bouncing around with engine rpm. Quite concerning

Cranking the engine with the valve cover off a pulsing "spraying" sound could be heard. A friend suggested, what if the head gasket was blown, and cylinder pressure was going into an oil gallery? Sure enough, when I removed the #1 glow plug the oil pressure gauge acted normally again, and no more pulsing / spraying sound, which I think is cylinder pressure making its way to the oil jet for the timing chain / vacuum pump.

My engine is newer - produced around 1998 - and has a #22 head. Kind of disappointing to have this failure, but at least a gasket and bolts aren't super spendy.

I did take a quick video of the oil pressure gauge: https://twitter.com/i/web/status/1673166619382788096

I'll share more once the head comes off...

Does anyone have a recommendation for the device to split the timing chain?

Thanks,

-Jason

dieselbenz1 · #2 06-29-2023, 08:58 AM

The no.22 head was never in a production car but was introduced later to address some faults. This suggests your engine has had a prior engine work.

It would be easier to zip tie the sprocket to the chain and unbolt it rather than split it.

compu_85 · #3 06-29-2023, 02:27 PM

Yes my car had a replacement engine installed sometime in 2001. The engine itself was made in 1998 based on the casting dates I've seen.

-J

compu_85 · #4 05-26-2024, 07:02 PM

Almost a year later, I'm digging into this.

The guide rail pins really fought coming out. The upper pin was quite stuck. After pulling the threads out and snapping the pin off twice with pliers I ended up drilling a hole in the back side of the head so I could drive it out. Even then it took considerable force.

Adding to this frustration a head bolt stripped as I was taking it out. An Irwn Bolt Out removed it though!!

So anyway, yes the gasket is blown. Just like the TSB on the last page here: https://www.w124performance.com/docs/mb/OM60X/OM603_modifications2.pdf

This despite the #22 head has the updated design meant to prevent this!

I'm debating if I should send the head out to be checked. The "burnt" side of the fire ring faces the block, the head doesn't appear to have any scorch marks in that area.

-J

Sugar Bear · #5 05-26-2024, 08:48 PM

I would absolutely have the head checked for straightness and the valves vacuum leak tested. If the valves leak test good I wouldn't do a valve job I'd just replace the valve seals. If they don't pass a leak test they need grinding.

Sugar Bear · #6 05-26-2024, 08:50 PM

The block should be checked for straightness, small spots can sometimes be corrected with a long file.

compu_85 · #7 05-30-2024, 06:37 PM

One interesting thing I noticed, the flange by the injection pump that I thought had no SN stamped into it does have a stamping: 603

Based on this note from Sixto my car has a complete replacement engine, not just a longblock:

Quote:

Originally Posted by sixto

If you have the numbers 603 010 06 50, you must have found a tag on the passenger side of the block. EPC says that's a replacement 603.970 short block. A replacement 603.970 long block (with head) is 603 010 30 02, a complete replacement engine is 603 010 69 00.

I'm curious to know if it has a #17 head casting.

I'm ordering parts now... well trying to anyway. Seems like no one vender can get all the parts (fuel line clips, both chain guide rail pins, etc)...

-J

JHZR2 · #8 06-01-2024, 07:32 PM

Sorry to hear this. It’s a way of life for the 350 engines.

t walgamuth · #9 06-03-2024, 05:25 AM

I'd look for a good used 300 engine.

Those pins are an excellent design and can be pulled using a 10 mm bolt and washers iirc. Don't touch them with vice grips.

compu_85 · #10 06-03-2024, 11:40 PM

All the threads pulled out as I pulled it with a bolt and washers...

So I measured the head bolts today. None of them were stretched at all. Kinda makes me wonder if they were under torqued?

Check out how the gasket blew right where the prechamber blasts it:

Parts are ordered, hopefully going back together soon!

-J

dieselbenz1 · #11 06-04-2024, 09:48 PM

Which cylinder is it?

compu_85 · #12 06-05-2024, 12:14 AM

#1, the failure was into the oil gallery. You can see the space for the timing chain / gear at the left of the image.

t walgamuth · #13 06-05-2024, 07:08 AM

Quote:

Originally Posted by compu_85

All the threads pulled out as I pulled it with a bolt and washers...

So I measured the head bolts today. None of them were stretched at all. Kinda makes me wonder if they were under torqued?

Check out how the gasket blew right where the prechamber blasts it:

Parts are ordered, hopefully going back together soon!

-J

You have to get a bolt long enough to use a good bit if thread. If a shorter bolt is used the threads will pull out.

compu_85 · #14 07-25-2024, 02:21 PM

Ya, I used a long bolt. I should have chased the threads first, rust in the the threads made the ends of the pins split.

After a long delay, parts are in and the engine is going back together.

I spent a little time polishing the valve cover and intake, big improvement in appearance! I also re-routed the wire harness under the intake instead of through the #5 and #6 runners. I moved a small bracket from the intake to the bellcrank rod pivot and cable tied the harness to it, this keeps it well clear of the accelerator linkage. That and some other tidying really reduced the "pile of spaghetti" look my engine bay originally had. I removed the fuel heater thermostat... I bypassed it 8 years ago when it started leaking.

Yes, I know the boost control and transmission modulator lines aren't hooked up properly. Getting all of that back to factory is a later project. Though I'm not sure I want to get the overboost system back to 100% factory since on the 350s the overboost system is activated with the cruise control. Might make the car too slow...

I need to do some rust remediation on the radiator support and false firewall before continuing. Hopefully I'll have time this weekend.

I'm also really eyeing up the euro/603.971 manifold without the stupid right angle DPF bypass pipe. Ahh... scope creep...

-J

JHZR2 · #15 07-25-2024, 02:38 PM

Quote:

Originally Posted by compu_85

All the threads pulled out as I pulled it with a bolt and washers...

So I measured the head bolts today. None of them were stretched at all. Kinda makes me wonder if they were under torqued?

Check out how the gasket blew right where the prechamber blasts it:

Parts are ordered, hopefully going back together soon!

-J

I know it’s obe but bolt and washers for that is scary. At minimum I’d want a thrust bearing in the washer sandwich. They make small ones for this sort of thing.