Pressurized coolant system = stick a fork in the head and/or head gasket. Look no further. All the signs are there and you have recent history with a severe overheat situation. R.I.P. If the head is coming off for a gasket, don't waste your time putting the 14 head back on. Find a 17 or later casting and use it as an opportunity to make the car reliable.

Don't waste your time with the leak stop snake oil. All it's going to do is contaminate your entire cooling system. You take a bad problem and make it much, much worse.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

As the coolant falls to cold temperatures. The coolant reduces volume I suspect. Relieving the system of pressure normally.

Test for pressurized hose to make pretty certain. Is probably at least six hours after the engine was last up to operating temperature.

Then the hose should be about as easy to compress as it would be with the rad cap off. The white smoke should smell a little like coolant I suspect.

I don't know why I even look at that stuff. Like throwing sand in your engine.

It's a tough call. This car is in rough overall shape with 360K+. Front end needs major attention and the tranny leaks. In addition some parking lot nimrod caved in the rear right passenger door. And the interior is dog eared.

__________________
1986 300SDL, 362K
1984 300D, 138K

Why not just replace the idler pulley, fan clutch, etc, and eliminate all that? People complain about it here a lot, but it's easy with the right tools and I am not even that good at working on cars lol. I just put the cheapest OM606 fan and fan clutch from amazon on mine and they work fine.

If you need a new head, I have a couple (#18 and #22) I could sell, or if you want a cheaper one there is a wrecked 87 w124 in the Richmond Pick-n-Pull with a #14 head There are actually two the other one isn't wrecked and has like 360k miles on it so I probably wouldn't take that one. I pulled the injection pump last weekend so it's already half taken apart, you would just need the bit for the head bolts, a way to pull the timing chain pins and a chain (to use to lift the head) to remove it.

I think mine probably has a leaking head gasket too, it pressurizes the cooling system enough to soak half the engine bay when taking the radiator cap off even if it sits for days, but I can't get any results on any of the tests for a blown head gasket/cracked head. I don't really drive it that much anymore, but I will eventually put one of the extra #22 heads I have on it.

I would definitely try the bars head gasket repair if you think that is your issue.
I recently either blew head gasket or cracked the head on my 85 TD. Last Fall I was towing something too heavy up a mountain and was superstoked to be running 70 with the ac on towing a no till seed drill that was probably 1000 pounds. Then the golf ball sized hole blew in my expansion tank. Car ran very hot and after that I could smell coolant in exhaust. It would start on 4 cylinders but eventually smooth out.
The car has 460K on it and is a rust bucket. Its not worth much effort, but I went to parts place and bought the $40 bottle of Bars. It has a double your money back warranty even!
I poured it in and left it for a couple hundred miles. Exhaust quit smelling but I had high pressure in my cooling system still. After a month my thermostat quit closing and the heat quit working. Car would still run hot when towing. (We tow a lot with this car)
I got into it again 3 weeks ago and drained out the bars and replaced the thermostat.
Now it runs just like it always did, no excess pressure in cooling system and I pulled Monteagle mountain with a Honda ATV on a trailer with no overheating issues. I am a believer. Its been now 3000 miles since the overheat so I don't know how long it will last.
In summary, I would try it, but be prepared to remove it once its done its job. The $40 bottle says you don't have to, but though it fixed the head problem, the cooling system did not otherwise like having all those solids in it.

__________________
1985 300 TD 448K
1984 300 TD 278K

1983 240D euro 240k
1994 f-250 idi turbo 330K
1986 f-350 IDI
1987 F-350 IDI

1985 JD 1050 4wd
1965 IH 3660

It's not good, either a head gasket or head. I'm a fool for this car, it runs pretty sweet in spite of the problems. I might take a look at that 14 head. But first I'd pull my own head and have it tested. If it was just a gasket I'd think I'd stick to that. Seems the 17+ heads are $1500 and up. I'd rather put that money into my 300D with 138K. I like the SDL better but that 300D has a lot more life left in it.

I just don't want to dump thousands into the SDL. Too old, too worn. I've seen some outstanding SDLs on Craigslist in the last several months in the $5 to $9 K range, cars with under 200k and looking really good.

__________________
1986 300SDL, 362K
1984 300D, 138K

Interesting, thanks for that. This car is almost at that point. It's a tough call.

__________________
1986 300SDL, 362K
1984 300D, 138K

It's not a tough call if you like the car enough .

You're in the Bay Area and there are plenty of OM603 powered cars running through the LKQ yards, the cylinder head complete is under $200 the last time I bought one, remove it your self or have the yard guy do it for you, under $50 usually .

Don't waste a penny on any # 14 head .

You simply have to begin beating the bushes a little bit or move on from this car .

Those head gasket repair snake oils -do- work but only if you take the time to fully clean the cooling system first and follow the instructions to the letter ~ almost no one ever does the correct step by step and then complains later when they fail .

My son does these and they work .

I don't, I'd rather drop $1,500 on the used head, touching up the valves and installing new stem seals, new gaskets and so on .

IF you like the car .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I like it, I've had some good times in it, even though I've only had it for about 60K miles. It was in pretty good shpae so I bought it with 303303 on the odo.

Some think me a fool but my family lives in OlyWA, I used to do these all day Craigslist rideshare trips back and forth. Usually costs me nothing but wear and tear on the car (not insignificant) but I don't need to rent a car while I'M visiting family. Last time I went it was $225 for the flight and $500 for a week's car rental.

Plus the rides can be a real kick. A good old fashioned road trip. Have met some outstanding people. Of course you never see them again but oh well.

The rear legroom is big for those trips. Plus the trunk. I'd usually have at least one volunteer driver, it was a kick to seat in the right rear spot. I could see all the gauges from there. It was wild to sit in the back. I could see what a large cabin that car has.

But metal fatigue is a reality. This car might have been slightly abused before me - long story. It gets to the point where needed repairs get ahead of me. And I'm not sure I can fix the steering (it's a bit daunting, never done it except in small bits) and pulling the tranny to put in new seals, well, not sure I'm strong enough for that anymore (68).

For example, this SDL has 248K, pretty clean - no way I'll get this one (Virginia) but I think I'd be better off buying something like this than put $3K into my car.

https://www.hemmings.com/classifieds/cars-for-sale/mercedes-benz/300sdl/2448855.html

__________________
1986 300SDL, 362K
1984 300D, 138K

Do you think it would cost $3k to fix? I have a #18 head I could sell for $375, then you would need the tools to remove the prechambers (~$400 if I remember right), have the head resurfaced (~$200 or so?), new lifters (~$150), head bolts and gaskets. You could probably do it for closer to $1500. Suspension would be another $1500 but they will all need it at this point, it really needs to be done every 200k so a different one will need the same work most likely. Other than removing the springs the suspension work is not too difficult, I have done it all a couple times.

Including fixing the front end and tranny seals, easily. And w/o those, putting in another $1500 you refer to is perhaps not the best investment. I experienced the W126 steering on an '81 SD I owned. Very sweet.

I just have to wonder if it has the life left to warrant the investment. The interior was pretty badly worn when I got it. Not just the seats. I have to check the tranny fluid every two or three days. I feel half criminal spilling that much tranny oil on public streets. But I gather that is a hard job and if you don't do it yourself not cheap at all.

If it's just a gasket, could be worth fixing that, putting it all back together again and having another look at it. Luckily I have good off street parking, I can ponder the next step.

But I get the distinct impression that the 603, while smoother and more powerful than the 617, doesn't match it in expected lifespan. I just put some good hours and $ into it, fixed some stuff (including one new caliper, normally I'd go in pairs) and that work could get next to no wear and tear. Odd feeling.

__________________
1986 300SDL, 362K
1984 300D, 138K

It's probably a matter of putting $3k into this car and driving it another 75-100k miles, or selling it for $1500 and buying another better one for $6k and putting another $2k into it. Depends on what seems like it will work out better I suppose. I intentionally bought the cheapest one I could find when I got mine ($880) because I knew I would need to put a lot of money into fixing the suspension, and the nasty interior was easily fixed by collecting good parts from Pick-n-pull. I do still need to swap the dash, but I have a good one waiting to go in.

Here we're back to the TRANS-X solution ~ I put it in my weepy 240D's slushbox when it began to drip too much ATF and it stopped the dripping cold for 40,000 miles and made the shifts better too .

The E-Bay one is nice, you could buy it and drive it home.....

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

TRANS-X? First I've heard of it. Worked with no ill side effects?

This tranny shifts just fine.

It's weird, today at Pick N Pull I saw an excellent looking rear passenger door to replace mine, this on an '87 420SEL. I'll bet it takes two men and a boy to muscle one of those doors around. My only other experience with that was a front door with my Bimmer E30 and that sucker was heavy.

__________________
1986 300SDL, 362K
1984 300D, 138K

That is a point. Driving a quality car for that distance is going to cost you something.

This car was a one owner car before me, they still had the window info sticker from the dealer. Purchase price $47K. Inflation calculator came out to about $98K.

__________________
1986 300SDL, 362K
1984 300D, 138K