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Old 05-09-2003, 11:17 AM
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Join Date: May 2002
Location: Central Oregon
Posts: 1,004
Blown radiator hose nipple...

Okay, I had the radiator nipple where the upper hose connects blow off on me while traveling through the mountains in the wine country of sonoma county two days ago. It wasn't so bad except that I was smoking a Lexus when it decided to let go and I had to let him pass me. Really pissed him off too.

So I whip the car off the road (turns out right next to a water faucet) and lift the hood (car is indicating 95 on the temp guage) thinking I had blown the upper hose as it has been looking bad for a while now. And find that the hose is off the radiator. Inside it, of course, I find half the nipple that the hose connects to. So here i am in the middle of nowhere with no cell service but I did bring my toolbox. 22 year old car = travel with tools...
Anyway to make a long story short. I was able to "just" reattach the hose to the 3/4 of an inch that was left in place but of course when I put the rad cap on and gain any heat at all the hose blows off. Stop, fill wth fluids, and try it again...
Same thing. BTW - Also carry a gallon of anifreeze with me, go figure.
So I'm getting a little desperate as I am in the middle of nowhere so I screw the radiator cap on to the first click only (pressure relief position) and drive. Staring at the temp guage to ensure no overheat. Hand near the temp wheel on the ACC to dissapate additional heat if needed. Damn thing ran great for 500 miles never getting above 85 degrees on the guage even climbing the mountains north of Lake Shasta with the hammer down. Got home yesterday afternoon with a new radiator in the trunk and going to do the install this weekend however these cars amaze me.

Anyway, just a word on running these old diesels without pressure in the cooling system. It worked fine for me. Now luckily it was only in the upper 60's to lower 70's but still blew me away that it performed like this. You coudl probably hot wire the aux fan too to add additinal cooling if needed but I didn't think of that until I figured out I didnt need it
'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique
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Old 05-09-2003, 11:50 AM
Fredmburgess's Avatar
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Join Date: Apr 2002
Posts: 358
Hey Fisherman,

Mine (84300Dt) did the same thing about a month ago. Just gettin it down the highway when I notice a bit of smoke (steam...) behind me. Pull over and, yep, the top hose connection broke off under the clamp. I did pretty much the same thing as you to get home..also had 50/50 water/AF mix in the trunk (hey, you never know..!).

Only difference is that I cleaned everything off with carb cleaner, used some JB weld and a clamp overnight, and stuck that sucker back together. 3,000 miles and so far, so good!

I'm like you, I guess. I've got some tools, a Haynes manual, filters, quart of oil, gallon of AF, mighty vac, and some handcleaner all in a nice black bag in one well in the trunk. Out of sight but...makes all the difference and lets me drive this sucker every day, everywhere, on business. I can always sort limp it to my hotel, lose the suit, and sort it out with a beer...

New cars (and bikes) are boring!

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Old 05-09-2003, 12:04 PM
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Join Date: Mar 2001
Location: Alpine, AZ / Green Valley, AZ
Posts: 733
Sounds good to me....
Being a belt and suspenders kind of guy, I always carry spare belts, tools, etc. The difference here is that I only carry water rather than an anti-freeze mix. I can always drain and add anti-freeze later, and you never know when you might have to drink the water you are carrying just to stay alive here in the southwest.

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Old 05-09-2003, 12:11 PM
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Join Date: Jan 2000
Location: PA
Posts: 5,440

Why wouldn't it cool OK with the pressure relieved. All the pressure does (besides blow out hoses, cores, water pumps,radiator nipples, etc) is to increase the boiling point of the coolant because its less costly for the manufacturer to make a pressurized cooling system than to make an adequate no pressure cooling system.

I run my 300SD and 300SDL with the pressure cap loose all the time. BUT, I use Evans waterless coolant with a boiling point of 375F, yes three seven five. It saves a lot of wear and tear on all the cooling components because it relieves the stress of pressure on them.

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Old 05-09-2003, 12:14 PM
edge's Avatar
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Location: CT
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Yeah, it happened to me. I wrapped a copper flashing material and JB Welded it overnight, so far so good. I don't want to spring for the radiator just yet. I'd rather have the eurolights first.Carrying a gallon of water and tools in the triunk well is a good idea.
85 300CD Signal Red/Tan sold
83 300D Manganese Brown 109K
97 E420 Midnight Blue 197K sold
98 BMW 328i Vert White 100K, sold
95 BMW 525i White 125K, sold
93 BMW 525iT Red 193K, sold
95 E320 Green Wagon 125K, sold
94 E320 White 127K, sold
85 300SD 156K Grey (Annie), sold
84 300D Lapis Blue 170K (Judy), sold
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Old 05-09-2003, 12:25 PM
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Location: PA
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What does "lease fin" mean

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Old 05-09-2003, 12:30 PM
Old Deis
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Must be the week for radiators to blow. I had the nipple break off on my SD Saturday. Fortunately the thing broke in my driveway.
I used some JB Weld to fill the hole and put a big screw in there to plug it. Then plugged the line to the small tank and drove it until my new radiator came in yesterday.
Seemed to work. The temp held steady at 85. I had noticed the old radiator was leaking occasionally around the seams, so just as well to replace it now.
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Old 05-09-2003, 12:35 PM
edge's Avatar
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Location: CT
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P E H, it means that the lease was finished and I turned the car back to the manufacturer or sometimes I would sell it above what the turn value was and pocketed a few bucks, edge

Last edited by edge; 05-09-2003 at 01:37 PM.
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Old 05-09-2003, 02:36 PM
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Location: Coarsegold Ca
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I forgot who makes a kit for the plastic radiator, but it has a metal part that slips inside the plastic neck, so that when you tighten the clamp it won't break. Of every part on the 123 that I have looked at, the plastic radiator was the only thing that I said... wheres the metal?

1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it
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Old 05-09-2003, 02:57 PM
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Join Date: Mar 2002
Location: SF Bay Area
Posts: 131
Last year when I changed the coolant, I put few coats of JB Weld on the upper radiator hose nipple.
That is my preventive measure.


1985 300D Turbo
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Old 05-09-2003, 04:55 PM
R Leo's Avatar
Join Date: Mar 2003
Location: En te l'eau Rant
Posts: 5,373
Coolant Surge Tanks Give Me the Willies!

I've had the willies since the first time I saw those coolant surge tanks under the hoods of my 123s. I thought, "Ohmygawd, these things are plastic, 20 years old and UNDER PRESSURE!!! Gads!!!"

But, after running these cars for a while, I realize that at 85 to 90C they aren't under all that much (if any pressure) in a system that is in good condition.

It doesn't stop the concern of a potential failure so it's good to know about Evans coolants.

PEH, can you tell us more about your experience with their product(s)? How long have you been using it? Pros/cons. etc.

Enquiring minds want to know...
Never a dull moment at Berry Hill Farm.
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Old 05-09-2003, 09:44 PM
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Location: PA
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R Leo,

I've been using Evans coolant for about a year now in my '80 300SD and '87300SDL. In normal operation I haven't detected any difference from reqular antifreeze/water coolant. On a trip thru the rocky mountains with Evans coolant, the engine temperature going up a long hill appeared to go a little higher, maybe 25F, than on previous trips with water/antifreeze coolant. However, as soon as I go over the top and start downhill the engine temperature returnes to normal. This was all done with the radiator cap loose and no coolant was lost.

I also use Evans in a Ford Diesel tractor/mower. The radiator screen gets plugged with chaff and with water/antifreeze coolant by the time the overheat light came on, the coolant was boiling and leaking out. With Evans coolant when the over temp light comes on there is no boiling even with pressure cap loose. When the overheating occurs, I stop the engine and remove and clean the radiator screen and replace it. When the engine is restarted it cools quickly.

The advantages are higher boiling point, non pressurized system, less corrosion than water system and less cavitation.

Only con is the higher cost, about $25 per gallon but this is reduced by the extra long life.

Go to for more information. You may get referred to another site where you can get more information and order Evans coolant.

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Old 05-09-2003, 11:16 PM
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Join Date: Nov 2002
Location: Wakefield, RI
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Hey PEH,
I have looked at the Evans website a few times. They get pretty technical about having air-bleeds in the system to prevent air pockets, etc. from occuring with their coolant. Since MB's are notorious for having air pockets in the cooling system what did you do, if anything to avoid the problems? Any other issues with conversion? How did you purge all the water-based coolant? Did you run the RV antifreeze/propylene glycol through it first? Inquiring minds want to know. Thanks, RT
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Old 05-10-2003, 03:25 AM
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Location: PA
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To get the old water/antifreeze out I flushed with water and a cleaner, filling and emptying twice. I hooked up a hair dryer to the heater core hoses an let it run for 24 hours. I also hooked the dryer to the filler neck and let the warm air circulate thru the engine and radiator and out the 2 drain holes

I had no trouble filling the 300SD but the 300SDL 6 cylinder engine was more difficult as they are known to be. I just kept running it and adding a little at a time until it was full.

No, I didn't circulate propylene glycol thru the systems first. Evans coolant NPG+ is 85% proylene glycol.

No other issues but is did take me days to do the conversion because of the slow drying process I used. A quicker way would be to fill with Evans after the flushing and run the engine above 212F, the boiling point of water by partially blocking the radiator with a piece of cardboard. This will boil the water out of the system.

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