OM603 #14 head finally let go I think. Wish I would’ve made a build thread for all the cool stuff leading up to the catastrophic failure but oh well.

Long story short, replaced original head gasket around 7k ago due to cold pressure and eventual radiator bursting. Put the car back together with new head gasket, head bolts, radiator, and the old #14 head which surprisingly didn’t show any cracks. Even ported the head too. The car was already turned up at this point: stock injection pump maxed, 18lbs of boost, and water/meth for cooling + extra fuel. She really moved out nicely but then came the dieselmeken pump. Managed to blow the stock turbo out of the water THAT NIGHT hitting 27lbs with the baby stock Garrett.

The very next day managed to fab an HX35 Holset turbo onto the car even with crazy ass USA manifold. Involved notching frame rail and chopping oil drain plus some intake crossover pipe welding. Man the hx35 is a slow spooler but once it’s lit... wow.

Even with the 7.5mm pump turned waaaay down, rolling second gear burnouts with a welded diff 32lbs of boost was wild and I can’t believe the trans was holding even with the mods. After romping on it for a couple weeks like this, I was cruising then BAM, it just spit all the coolant out the tailpipe IMMEDIATELY. Pegged temp off the gauge. Managed to drive it onto the trailer the next day but it was partially hydro locked and maybe running on 4... I’ve totally signed off on this head + bottom end I think.

So ironically a day or so before it let go, I’m browsing car part and find a 606 somewhat locally but stupid high miles. I kinda laughed it off at the time but I think now it’s my only option LOL. In all honesty I had planned on swapping in a Chevy v8 if this happened but after experiencing how good the diesel pulled and having a pretty penny tied up in a superpump, I’ve gotta keep rollin coal for the diesel gang

So.... checklist for swapping into a 300SDL? I’ve heard the main concerns are oil filter housing and oil pan + pickup? (Pan and pickup potentially only other chassis concern I hear; aka non issue in w126 with no toll bar)


I’ll get you guys a couple vids uploaded of how this thing pulled... the 40-120 was mental. Hung with an S4, S6, and a tuned 335i twin turbo. Total grandpa-mobile sleeper til they hear the spool

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{2010 Mazda 3 266,000mi} - daily since new, Airlift suspension + some chunky sway-bars: fastest pass 17.7@77MPH
{1987 300SDL 256,000mi} - stock turbo @ 22lbs straight piped + a whole bunch of pre-turbo water/meth injection, 722.3 with increased line pressure, special sauce, and shift kit: fastest pass 16.5@82
{1992 964 Carrera 4 Frankenstein ??,???mi} - 993 forward dated, Speedster conversion, GT45 + E85: fastest pass 12.5@113

Your pan, oil filter housing as well as engine mount arms from the om603 will swap into the 606 no problems. Good luck with the build, looking forward to updates

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97 e300d, 78 300Dt, 95 E300d, 94 E320 estate

Here’s just rolling into it in 4th gear... just slingshots off the torque converter at peak torque. Thing just packs up and moves for a 4000lb freight train...

https://youtu.be/Idy5UMKqVD0


And here’s my best attempt at a 0-100, the car moves out slow AF in 1st then violently hits boost end of first and slams 2nd gear spinning.

https://youtu.be/g3FtEewP14w


0-60 in 6 sec range spinning badly lol.

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{2010 Mazda 3 266,000mi} - daily since new, Airlift suspension + some chunky sway-bars: fastest pass 17.7@77MPH
{1987 300SDL 256,000mi} - stock turbo @ 22lbs straight piped + a whole bunch of pre-turbo water/meth injection, 722.3 with increased line pressure, special sauce, and shift kit: fastest pass 16.5@82
{1992 964 Carrera 4 Frankenstein ??,???mi} - 993 forward dated, Speedster conversion, GT45 + E85: fastest pass 12.5@113

Check out diesel pump UK for info on a 606 swap.

Not a "plug and play" swap, will cost you way more in time and money than the car is worth but if you're mechanically very advanced and patient it is very rewarding.

I think room for an intercooler and a strong enough transmission will be an issue too. It seems like mounting a VW 1.8t intercooler on the passenger side similar to how the oil cooler is mounted might work, the transmission I'm not sure. I haven't seen enough evidence that the 722.6 standalone controllers work well enough to take the risk, maybe a built 722.3 or a manual swap would work. I'm probably selling my SDL anyway but I had thought about swapping in an OM606 until I started thinking about all the details involved to get it running.

If you aren't afraid of a bit of fabrication, it isn't so bad. I've been slowly putting mine together (I'm worn out and crippled most days), working on wrapping up the wiring and final bits here in the next few weeks. It is definitely not cost effective or easy if done right, but hopefully it'll be worth it.

Here is my thread on a 91 350sd 606 build:

W126 short body OM606


If you are already running a 7.5mm pump, get a 722.6 or beef up the 722.3 if you are set on keeping that original. It'll cost way more to build up a 722.3 over a 722.6 since there are so many performance applications already running the .6. If the SDL didn't have the bigger flanges on the diff, swap a V8 flange over and use V8 flex disks from a w220. You may have to shorten the shaft a little, however mine barley fits with the 3 piece driveshaft found on the 350sd. We'll see how those flex disks hold, I may swap over to the w220 AMG 4 finger disks if they start shredding, but I'm going to keep this one under 500hp as it'll be a daily and I want it to last awhile. CVs will probably go, CVJ in Denver can beef up a set for you if they are still around, they were the only ones who could build a set that would hold up in my 83 better than stock. Intercooler is easy with US bumpers, I went way oversize on mine (sized for 700hp) as my daily drive involves a very long uphill pull and I want this one to run as cool as a cucumber, even thought it'll cost me some off the line. Check out the setup awsrock put under his bumper later on in that post, that is likely sufficient for most setups.

It would be easier and likely cheaper to buy a E/S55 or S600 if you are after speed and reliability, but if you are as twisted as some of us I'd say go for it.

Interesting turn of events... the OM603 might be going back together. Even weirder yet, there’s a chance even the #14 head casting has survived a second gasket failure and overheat... which is nice I guess as I just did head porting, lifters, valve stem seals + lapping. The last head gasket failure was more gradual starting with cold coolant pressure and oil leak but never an overheat. This was how I purchased the car.

This time after 2.1bar/32lbs of boost and how rapid the whole cooling system exited out the tailpipe, I figured the head was cracked for sure. Temp gauge was off the map after pulling to safety. Looks like the head lifted though and the fire ring between 5 and 6 couldn’t hang... (Victor Reinz gasket for what it’s worth, I know people talk badly about them but I think the power was the culprit here).

The reason I ended up tearing into the engine even after signing off on it was because I figured the 380,000 mile OM606 probably didn’t have enough life left in it to rationalize just dropping it in and beating on it racecar style. Another motor that was listed nearby for a fair price and low mileage turned out to be an incorrectly listed E320 gas V6 So I figured I better see what’s up with this motor. With the (at least currently) lack of carnage, it looks like I’m a monkey test pilot meant to take this #14 casting to the moon and back Time to stuff an OM606 MLS gasket in there and see if I can find some head studs for some clamping power. The “upgraded” head bolts seem not enough.

Attached Thumbnails

 

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{2010 Mazda 3 266,000mi} - daily since new, Airlift suspension + some chunky sway-bars: fastest pass 17.7@77MPH
{1987 300SDL 256,000mi} - stock turbo @ 22lbs straight piped + a whole bunch of pre-turbo water/meth injection, 722.3 with increased line pressure, special sauce, and shift kit: fastest pass 16.5@82
{1992 964 Carrera 4 Frankenstein ??,???mi} - 993 forward dated, Speedster conversion, GT45 + E85: fastest pass 12.5@113

I’d bet an elring klinger om603 gasket would hold up better than vr.
MLS are even better, but much less forgiving of any surface imperfections in block/head.
If properly maintained: 380kmiles may last quite a bit longer
Good luck with the build either way

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97 e300d, 78 300Dt, 95 E300d, 94 E320 estate

Does anybody install ss o-rings in these? All the race motors I built, we cut in grooves in the block and set stainless o-rings on copper gaskets. Just a thought.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

That is awesome. I like vstech's idea for fire rings, lot of the high HP cummins are running those if you can find somebody who can machine in the groves.

Hope this round lasts a bit longer!

After a whole night of researching the topic, I came to the following conclusion about OM606 MLS gasket on a 603; will it work? Maybe... and for how long. It seems the surface finish of the head casting is fantastic but the block is a very high RA better suited for composite or copper gasket. The water jackets inbetween the cylinder bores seem to be problematic for the 603 using a 606 gasket. For me and my current situation not wanting to dump money into the 603, the prep work required to make the MLS gasket makes it not an option.

Furthermore, I don't think gasket quality caused the failure in this instance; it's pretty clear the head was lifting from cylinder pressure and moving around. The block side of the gasket looked like it stayed put and the head side had some light abrasions around the fire rings even on the cylinders that didn't let go. All the *uprated/new* headbolts I bought before the last head gasket install all measured out to spec; no stretch. It's clear they can't hang though...


I've been busy planning and missed these last few posts but it's funny you mention that because...

STATUS UPDATE! bought that OM606 turbo with crazy high mileage after they sent a video of it running in the car still. The game plan is go through the 606 slowly and clean, re-seal, and fortify it for BIG power while I rock the OM603 once it's all back together.

Speaking of putting it back together, just purchased a block o-ringing tool from Isky Cams, some 0.041 stainless steel wire, and a custom set of studs from ARP (don't ask on price... I'm still spinning and need to take a seat).

Looks like we're going on a journey folks; follow me to see the farthest a #14 head casting has ever been pushed. Some real clamp loads and fire-rings ought to show what a 603 is really made of. Here we go!

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{2010 Mazda 3 266,000mi} - daily since new, Airlift suspension + some chunky sway-bars: fastest pass 17.7@77MPH
{1987 300SDL 256,000mi} - stock turbo @ 22lbs straight piped + a whole bunch of pre-turbo water/meth injection, 722.3 with increased line pressure, special sauce, and shift kit: fastest pass 16.5@82
{1992 964 Carrera 4 Frankenstein ??,???mi} - 993 forward dated, Speedster conversion, GT45 + E85: fastest pass 12.5@113

I’ve got a 1997 300d with great om606na in it. It needs a good home. Good for parts or fix the things wrong with the body. Needs bumper some interior stuff and motor mount.