I've been doing some interior rehab work on my '92 300SE. Unexpectedly, my consulting work ramped up considerably, eating up all my spare time, so the car was relegated to my storage shed.

I've been fighting with a few ticking hydraulic valve actuators. They tick rather loudly at first startup, most are quiet by the time the oil pressure gets to 3 on the gauge (1-2 seconds tops). A few reluctant souls continue to tick until the oil warms up a bit.

Anyway - I thought about doing that work myself, but reading all of the cautions on AllDataDIY about the timing chain tensioner and proper reinstallation of the intake cam adjuster, I was reluctant.

Dawned on me one day that I could just pay my mechanic to do the work and not have the worries noted above, plus I'd get a warranty on the work. $ are more plentiful with the extra consulting work.

Went to the shed to get the car out to take it to the mechanic. It starts just fine - but not a SINGLE TICKING NOISE is to be heard. How frustrating... maybe I said "repair shop" within it's hearing range? Anyway - starts right up, but there's a bit of a miss at idle. Clears up after a few seconds. I chalk it up to sitting for 6 weeks without being run.

Drive it to the mechanic, and I'm sitting at a stoplight. Windows are down and the wind is coming from the rear of the car. I smell antifreeze... I look in the driver's door mirror and see steam coming from MY CAR... uh-oh.

Now I know what's causing that pesky coolant loss...

Get it to the mechanic. He's a detail-oriented individual. Won't do work on cars if the customer tries to nickle-and-dime the process. I trust him and his group completely. Labor rates $90/hr - maybe a tad more than some shops, but way less than the dealer. He works only on German cars. Shop is immaculate - has all of the right diagnostic tools.

They agree that the headgasket is leaking. The cold start miss is from the moisture in the cylinder where the coolant is seeping in. Oil is still right color, so no fears of further damage due to coolant contamination there.

I purchased this car from my inlaws who own a repair shop. (Nothing more expensive than a cheap Mercedes...) They bought it from the previous owner when it was brought in for a blown headgasket. The owner popped the serpentine belt and ran it until it overheated so badly the gasket blew. Father-in-law's work ethic is one of "fix it and get it gone so I can get paid" - (which explains why noone ever comes back to his shop for further work). I've spent 100's of $ re-repairing things he "fixed" on this car. I always wondered how long his headgasket work was going to hold. Now I know - about 30,000 miles. When I got the car, it leaked coolant. Every coolant-related item that was removed from the engine during his rebuild was reinstalled, not with a new o-ring, but with the original o-ring and orange hi-temp silicone. The total cost of o-rings for the cooling system is probably less than $10. Worst was the connector at the back of the head against the firewall. A 10-cent o-ring, the R&R of which took me 6 hours...

To continue my rant...

Get a call a few days after dropping the car off. "Do you want the bad news, or the bad news?" The head is below spec. It's already .005 under. Apparently, it was warped badly with the first failure, or the machine shop just butchered it. This explains why I was never able to get the eyebrow oil seal on the front of the motor to seal right. It was getting crushed and distorted when I would tighten everything back up.

He continues - and here's where it gets worse (if you can imagine). Even if the head was millable, it's still scrap. Why? Because whomever reinstalled the head neglected to put the stress washers back under the head bolts!!!! All of the "bolt towers" were mushroomed. Had to use an impact wrench to get some of the bolts to come loose, they were so galled into the aluminum.

My FIL's group was probably wondering where all the extra washers came from after they finished the installation...

The failure to use the washers is probably what lead to the failure of the headgasket. Once the structure of the bolt/head mating surfaces in the head was compromised, they continued to deform in service, releasing the tension on the bolts, and hence on the gasket.

I authorized the mechanic to also replace any items that are easy to get at now, hard to deal with later.

So - add a new oil cooler and housing, plus the bypass pipe that feeds it to the list of parts which include:
Timing Chain Tensioner
Gasket set
Plugs
Wires (they were original!)
Oil
Filter
24 lifters (just to be sure we don't put one of the tappers back from the original head)
used cylinder head

20 hours labor - higher than standard book hours, but extra work for the oil cooler, and the additional labor to get the head out in the first place.

$550 machine shop costs - mill head and replace everything that needs it.

I'm looking at a $5000 repair bill.

For a car that isn't worth $5000....

I love the car, and since it's paid for, assuming I don't get stung with some other high-dollar repair in the next year or so, it's still cheaper than a car payment.

But daaaammmmm!

And it still needs a paint job...

And the interior rehab is still in-progress, which means a gutted interior...

I'll be lucky to be back in the car by fall...