Change out your radiator if you think it is old or Original. - PeachParts Mercedes-Benz Forum

ah-kay · #1 06-11-2022, 01:35 PM

My car 1987 300D had a near death experience last week. It was turning 400k miles on the way back from San Francisco. A milestone reached so to speak. However, when it was climbing Los Angeles National Forest the radiator neck snapped and lost most, if not all, coolant. It overheat big time. Luckily we were near the top of the climb and limped to

Fort Tejon State Historic Park

https://g.co/kgs/TjZDaU

The break wasn't a clean break and I couldn't attach the upper hose back on. I had it tow home. Ordered a new radiator and car is now back on the road. So check your radiator and change it out if necessary, plastic radiator is prone to breakage.

Alec300SD · #2 06-11-2022, 03:14 PM

Yes, plastic end tanks on radiators (and intercoolers) don't make sense for parts longevity.

My new DD, 'Kjetteri', developed a mystery coolant leak with a tiny bit of foam in the coolant expansion tank.
Turned out to be a cracked plastic radiator nipple, and not a head gasket failure.

On Monday morning I bought a 3/4' X 1/2" PVC coupling and 2 oz of epoxy putty to repair the nipple in the afternoon after the car was cold.

On the way to work, steam started wisping out of the left front of the hood, so I did an emergency roadside repair.

The plastic end tank still leaks a tiny bit of steam from a crack between the top overflow nipple and the top hose nipple.
A replacement radiator will be installed...if I end up keeping this 'Heresy'.

speednjay · #3 06-11-2022, 05:26 PM

If you need a hand with anything I’m not too far away. I can grab a radiator from my 94 and bring it to you.

Jarod · #4 06-11-2022, 06:18 PM

I just had a coolant bottle explode.
No excessive pressure, possible prior trauma from an overheat long before I got the car, but has been fine for years now.
I went ahead and replaced the overflow tank and cap just in case, car is running a-ok again, incredibly it blew out in my driveway right as I got home one day.

unkl300d · #5 06-11-2022, 06:20 PM

It happened to me when I used to own the w126 1989 300SE.
Luckily right before entering the freeway bridge entrance on Turkey day!
I stopped immediately.
Fetched some water from a near by store.
was able to keep the neck closed with the 'mechanical' hose pressure,long enough to drive back home. (maybe 6 miles).
Did not overheat.
I think I saw the steam just before entering the freeway... long ago....

replaced the thermostat cover with an aluminum one, the original was plastic, and also replaced the radiator because the neck edges were deteriorating.

dieselbenz1 · #6 06-11-2022, 07:37 PM

It happened to me and about a year latter it needed a head gasket and the head flatted. That's one pattern I've seen several times before.

jdulle · #7 06-11-2022, 07:44 PM

Glad you have it running again, and it wasn't too catastrophic.

BillGrissom · #8 06-11-2022, 09:48 PM

For those with W123 300D, new radiators are now affordable. I got one for $130 vs used to be $350. That solved the overheating in my 1985 300D after trying many other things over years, even another used radiator first left sitting with citric acid for a week. That climb on I-5 N out of the L.A. Basin, on a >100 F day, is where I have heard new car coolant designs are verified. If you go up the grade slower, that will reduce the horsepower output of the engine, if fighting an overheating issue.

Shern · #9 06-12-2022, 12:45 AM

Quote:

Originally Posted by BillGrissom

That climb on I-5 N out of the L.A. Basin, on a >100 F day, is where I have heard new car coolant designs are verified.

This.

When needing to verify work I’d done to my cooling system, this was the proving ground.

Screwdriva · #10 06-12-2022, 05:51 AM

Uncle Kent sells a reinforcement kit which is quite effective at preventing this exact issue.

HughO · #11 06-12-2022, 09:50 AM

Quote:

Originally Posted by ah-kay

My car 1987 300D had a near death experience last week. It was turning 400k miles on the way back from San Francisco. A milestone reached so to speak. However, when it was climbing Los Angeles National Forest the radiator neck snapped and lost most, if not all, coolant. It overheat big time. Luckily we were near the top of the climb and limped to

Fort Tejon State Historic Park

https://g.co/kgs/TjZDaU

The break wasn't a clean break and I couldn't attach the upper hose back on. I had it tow home. Ordered a new radiator and car is now back on the road. So check your radiator and change it out if necessary, plastic radiator is prone to breakage.

MS in Bellingham has issued a warning on this and recommends a copper sleeve inserted inside with epoxy to reinforce it. He sells the components. it is a known problem and why these car companies think that plastic radiators caps are acceptable is beyond me.

ah-kay · #12 06-12-2022, 12:04 PM

You can reinforce it all you want but the breakage is at the base of the neck and took out a bit of the body itself. Basically no 'neck' left. The kit would not help. The breakage is a crapshoot thing so you take your own risk.

ykobayashi · #13 06-12-2022, 12:38 PM

Yah. I can remember all my breakdowns on Tejon pass. living between the Bay Area and Socal we drive this all the time. I think we’ve had four coolant system failures there over fifty years. Most were in my childhood because my dad was an optimist driving his dodgy cars over the hill during summer. My MBs never failed there but they did get hot on occasion and required turning on the heat. My wife and kids hate that part. Sweltering day “we are turning on the heater full blast!”

My rad neck popped a decade ago in SoCal I was taking my FIL out to lunch and it just popped. Luckily there was 1/4” left on the neck and I managed to slip the hose and clamp back on and I wired it with safety wire to the bolts on the oil cooler and possibly elsewhere to secure it temporarily. I recall walking into a restaurant and getting some water out of their sink with a milk jug and refilling. Got back on the road in half an hour.

When I got home I watched the uncle Kent videos. He has a funny one where he tells what a great guy he is for grabbing somebody’s rad neck and giving it a shake and then breaking it off. “See I saved you a breakdown.” Interesting how he convinces himself how wonderful he is. I’m sure the person with the snapped radiator is speechless. He does have a point though. Just an interesting psychological response on his part. Reminds me of some friend “hey man you should be thanking me!”

His kit is basically a piece of copper plumbing and some JB weld. There is a size at Home Depot that fits right in there. On prior cars I bought one and glued it in. Maybe I should do it again. I’m sure there’s a thread here about which pipe exactly to use. If you cannot find it, measure it and go to Home Depot and find the tube.

Let me check my notes. I bet I wrote it down. Huh…my notes are here. Brought back some bad memories. Maybe I should reinforce my cars…both have new radiators since I wrote this.

Plastic radiator neck cracks

dieselbenz1 · #14 06-12-2022, 03:58 PM

A constant tension band should be used rather than hose clamp just like the newer models with the same plastic neck and no issues with them snapping.

BillGrissom · #15 06-12-2022, 05:57 PM

Quote:

Originally Posted by ykobayashi

Yah. I can remember all my breakdowns on Tejon pass. living between the Bay Area and Socal we drive this all the time. ...

On both high passes climbing north out of the L.A. Basin I-5 N over Tejon Pass (4100 ft) and I-15 N over Cajon Pass (3800 ft), you see cars on the side with hoods up every 1/4 mile on a hot afternoon. Seems most common in late Spring after owners didn't check coolant level all winter. Even with proper coolant and pristine parts, new factory designs can barely handle the power output of those steep climbs at the 70+ mph many drivers attempt. There are a few emergency water stops.

A less challenging route to the Central Valley follows the rail lines: CA-14 to Palmdale (3300 ft pass) then US-58 to Bakersfield (3800 ft pass), and is less often snowed-in. Drivers going to SF Bay can take U.S. 101, also a rail-line with just an 840 ft pass to Ventura. Last time I-5 closed for snow, the Tesla Supercharger in San Luis Obispo was overwhelmed, with 6 hour waits to charge. Leaving the L.A. Basin going east only climbs to 2600 ft (I-10).