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) then US-58 to Bakersfield (3800 ft), 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).

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Mine blew on my 83 300D after only 3 laps of a track, then I drove it like that for like 3000 miles including a giant roadtrip, before replacing it with the new style with the wonderful baffles and the level sensor blockoff

Welcome to the 400K mile club!! Your 300 D looks awesome!

My ‘78 300 CD (C123) has 415K miles. It was my daily driver for many years, but is now driven on nice days when I can put the sunroof back and windows down and enjoy pillarless driving!

Jim
‘78 300 CD

My 1985 CA 300D has 380K miles, but the original engine failed at 330K, then found a pristine used engine (>400 psig compression all cyl). The original paint has failed clearcoat from the evil CA sun but about to repaint it. Daughter crashed it (totaled USPS Transit van which hit her side front) so I bent the front rails back and got new fender and hood from a 1983 (given whole car less engine, doors, & glass). Since the 1983 had been recently painted in a modern grey-blue, I also took other fender, trunk, and sunroof, so now only need to paint half the car. If your 1978 is non-turbo, the engine will likely last much longer. I suspect those were the 1M-mile engines.

__________________
1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

Bill:

First engine died in 1997 when the timing chain broke and lifted cam tower off of the head. That was 8k miles after the chain was checked and cleared. Got another engine and had it rebuilt at Metric Motors as I planned to keep the car. Still going strong. Over the years, I have rebuilt the car twice due to living in areas with winter road salt and then areas with desert heat (military). The last refurbishment was performed while I was in Japan for seven years. It currently looks very nice for such an old gal (Dick Clark/Christie Brinkley genes!). The only original parts left are the trunk lid, roof, hood, and a few interior pieces.

Jim
‘78 300 CD

Attached Thumbnails

 

Kent has some good ideas and some goofy ones. This copper sleeve in the radiator neck idea certainly is one of the latter as he doesn't consider the reduction of coolant flow, albeit minimal . An acceptable idea, however, if you happen to have a piece of copper tubing during an emergency, but just as a bandaid to get you home.

__________________

Don't Chrome them; polish them

My 90 w124 diesel had the radiator neck slightly weep , took me a long while to figure out what was going on as coolant loss was minimal and it ran down side of rad hidden from view and the small amount evaporated away before it could even hit the floor.
A combination of old rad and worn engine mounts and a very old stiff top hose tugging at the rad when engine moved was the cause.

We have read here that the upper plastic nipple on the radiator cracked at the base of the neck and another person said it cracked further out. I suspect unless Kent's idea of a copper sleeve/epoxy reinforcement would help if for no other reason than it spreads the stress out all over and around the hose nipple. I decided to do my own version using the MS method. I used powdered copper as an epoxy thickener which gives astounding strength probably better than the powdered aluminum of JB weld. I also cut pieces of graphite cloth/epoxy around the base and up to the flange for the hose, carrying the load almost an inch on to the radiator cap housing all around to a thickness of 3/16-1/4". This gives what amounts to an epoxy gusset. Curious that nobody mentioned failure of the lower radiator hose nipple, perhaps because it probably runs a little cooler?

This is my take. You can reinforce it all you want but it doesn't resolve the fundamental problem of plastic fatigue. The breakage can be at the neck, at the neck base or thereabouts. You may end up with no neck to speak of. This is what happens to me at the most inopportune time. If the car is a keeper then just replace it for not so much money. I have a #14 head on the 87 300D so any overheating is a death nail. If you want to do any preventative maintenance then this is it.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

I always wondered what the failure mechanism was. On my car I think I overtightened the hose clamp for starters. I really got over enthusiastic about squeezing that hose on tight for a good seal. When it broke there was a nice dent all around the nipple where I’d crushed it. Second, my engine had a lot of shake. It was a rocker. Like somebody else said above the rocking may fatigue the hose. I’ve since solved my engine shake so my new radiator will hopefully last.

JB weld is filled with steel or iron powder incidentally. I glue magnets to items with it and it makes for some really interesting fluid effects as the magnet pulls the epoxy to all the wrong places.

Maybe the pipe insert is useless. I don’t think it hurts. On my car it broke right under where I had the hose clamp. I want to put a tube in but I stopped when I saw the price of 1” copper tube. Dang has that stuff gone up in price or what!

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

Problem with this car again. May be the head was weaken during the climb and overheating. Car is old and high mileage so don't want to spend the effort and money to change out the head. I have a spare #14 head from a forum member.

Anyway, I put the money where my mouth is. I just use Blue Devil sealant on my 1987 300D. It has 410k miles. The radiator bursted at 400k while climbing Los Angeles national mountain on I-5. Very steep and long grade. Car overheated but I think I stopped in time. Changed out the radiator and car did another 10k without issues until 2 weeks ago. It overheated and I did the radiator overfill test and found the head is done for. Coolant overflowed whenever car is run. Long story short, use Blue Devil sealant and the cracked head is sealed. It passes the overfill test and did about 300 miles so far. Radiator hose is soft to touch every morning so no build up of pressure. Jury is still out but I will update at 5k, 10k etc.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Wow ah-kay, I am surprised that the red devil sealant did not clog smaller cooling ports inside of engine.

Good luck !!

__________________
1979 300D 220 K miles
1995 C280 109 K miles
1992 Cadillac Eldorado Touring Coupe 57K miles SOLD
********************
1979 240D 140Kmiles (bought for parents) *SOLD.
SAN FRANCISCO/(*San Diego)
1989 300SE 148 K miles *SOLD

I am surprised that you are so misguided. Blue devil will be out of business if it clogs anything.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Well, it clogs the leak in the head gasket.

__________________
Te futueo et caballum tuum

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

I have bought 2 in the last month . Same here with the neck . I’m considering a new hose first if the ones look fairly old . It might be the rubber hose is so old it won’t seal , then you go to seal it off with tightening the hose and it’s over pressure on the plastic . Servicing the rest of them with the new hoses and come back with any problems if found .