Coolant leaks and general weirdness. - PeachParts Mercedes-Benz Forum

rwthomas1 · #1 05-26-2003, 01:22 PM

I had chased coolant leaks and finally fixed them all but I now have issues again. '84 300D, fine around town and short 1/2hr to 45 minutes everything appears normal, no coolant leaks anywhere. I drove to Washington DC last weekend and I noticed the overflow tube puked some coolant into the fenderwell. It did the same thing on the way home. Not enough coolant to see a visible drop in the plastic tank but puking some nonetheless. As an experiment I loosened the radiator cap one click so the cooling system would not pressurize and drove the car out to western MA on business this week. Ran fine, no puking coolant, no overheating just the coolant level rising about twice as high as it normally does in the plastic tank, due I suppose to expansion? I tightened the cap again and drove home. Now I have coolant leaking from somewhere under the waterpump. Not a large amount, maybe 6oz max. So here is what I am thinking:

1. I have a small headgasket leak. My coolant hoses are firm even when the engine is dead cold. Not as firm as when hot running but definitely there is pressure in the system at all times. Could the combustion gasses be "burping" out of the system during extended high-speed cruising causing the puking of some coolant out the overflow tube? I know that headgasket issues are almost unheard of in 617 engines but its possible.

2. My "new" leak under the waterpump is either coincidence, the waterpump just decided to start to die after the two long drives or maybe the seals need time to "seat" again after pressurizing/depressurizing the system a few times.

3. Where is the coolant level supposed to be on the plastic tank? I fill it to the little line/arrow mark when cold. The coolant level rises about a 1/2" above that when fully warm, due I guess to expansion? Sound normal? Should the coolant level be at that line when hot not cold? Is there a "minimum" mark on the tank? Should I drain it to that point instead?

4. I am sick and tired of dealing with this issue and I will be contacting Evans Cooling this week to consider the possibility of using their NPG+ coolant and going the a non-pressurized cooling system. I realize this may just mask another problem but if it runs well, doesn't leak anything and doesn't overheat I will be happy.

5. Is there any harm in running standard coolant with the radiator cap loose? When I did it there was no sign of overheating, no leaks, no issues? Maybe hotter weather would give me trouble but then again maybe not... As long as I keep a close eye on the temp gauge I don't see how it would hurt anything.

Oh yeah, at no time has the temp ever exceeded 95*C so its not overheating. Any ideas on this problem would be great. Sorry for the long post, just trying to put it all down. RT

engatwork · #2 05-26-2003, 01:29 PM

My first thought is maybe your radiator cap ain't right. I'm wondering too if your water pump may be suspect. Can you tell if the leak is coming from it? Tomorrow morning, before you start the car remove the radiator cap and see if the cooling system is "pressurized". If it is then you have a head/head gasket issue.

rwthomas1 · #3 05-28-2003, 12:35 PM

Evans will cost me $90 to convert. Not bad for "lifetime" coolant but the car just pi$$ed me off so I took action, for better or worse.... Yesterday I turned the ac on and the "EC" button on the ACC unit flew off as it popped out, over my shoulder into the back seat. Thankfully the ACC unit still functions fine, I can still push the stalk the button mounts on to activate it, and I should be able to just dab a little Goop on the button and stick it back on. Since I have just started to smell a slight whiff of coolant coming from the heater vents I now know I have a heater core leak too. This has pushed me over the edge with this car and here is what I did: Removed stealership-purchased 1.4bar $26 radiator cap and threw it into the woods. Went to Autozone and purchased a 7lbs usa-made radiator cap for $3.99 and a bottle of Bar's Leaks. Drained the radiator and poured Bar's into the upper hose, refilled, installed 7lb cap and when for a drive with heat on full for 45minutes. (drove to Krispy Kreme to soothe my temper) Rerouted vent hose from plastic expansion tank to hole in fender with a plastic 90* aquarium fitting. Now vents to fenderwell so I don't have to look at the little coolant dribbles. 7lbs cap, less pressure in the system=good, Bar's Leak in the system=questionable, but if it fixes the leaks......, Vent line to fender hole=good, outa sight-outa mind. So far so good. Watch the gauge, keep and eye on the coolant level and not worrying about it anymore. Happy motoring! RT

Stevo · #4 05-28-2003, 11:00 PM

I would put a clean piece of cardboard or whatever on the floor under the water pump and if I found coolant in the morning

the water pump would be highly suspect, ...just a thought
Good luck

P.E.Haiges · #5 05-29-2003, 10:11 AM

RWThomas,

I run both my one 300SDs with the radiator cap loose most of the time. The one has regular antifreeze/water and the other one has Evans coolant in it. They are both old and I figure why put strain on the system by pressurizing them. The only difference I have found is in very cold weather, the heater doesn't put out as much heat.

The no pressure antifreeze/water coolant may not work in extrenly hot weather or high altitudes, but it works for me here in PA most of the time. The Evans works all the time, hot or high altitude.

P E H

dabenz · #6 05-29-2003, 01:20 PM

ditto P.E.H. The pressure is there to give the engineers (and you) a margin of temperature safety on the hot side. More pressure means more heat can be absorbed by the coolant before it boils. It also means all the seals have to work harder. In the end it's a matter of your particular driving environment and your experience with the car.

#7 05-29-2003, 05:05 PM

Greetings Rob,

Ew missed you at the Hartford gtg. It was an enjoyable time for all.

Anyway, first I'll comment as to your windshield sealing experience. \Nice write up. One day I intend to tackle the rear winshield in the Black Bomber,,,,,,,,the rust IS under there and WILL require a CORRECT repair.

Next, I HAVE used Barrs Leak previously.....NOT IN THE 300d mind you.........only in my previous P.O.S. ford taurus (the 3.0 litre, NOT the 3.8 that tends to overheat. Note: the LIQUID Barrs Leak was what I used.

The taurus P.O.S. heater core is a badly designed piece of crap. However, the LIQUID remedy noted above enabled me to POSTPONE the heater core replacement on 2 occasions! Each application worked for aprox. one year of daily HARD use. On ANOTHER note, last winter, my fiance had the same steaming defroster vents in her FORD (ie; lincoln 3.8) and AGAIN the stuff seems to continue to hold back the steam leak. Remember that I am NOT speaking about my baby, The Black Bomber. The replacement of the heater core in the taurus cost me $500 by a ford tech that performed the "surgury"........the ENTIRE dash assy MUST be removed for this damn mess!.........never buy another ford again.............and I will NOT even mention their transmissions!!!!!!!!!!!!!!!!!!

The 3.0 motor NEVER had any headgasket trouble whatsoever. With luck the lincoln 3.8 will stay alive until we can find a NICE 300d for the lovely.

The 300d radiator cap came with a factory marking of "100"...later, Mercedes uprated the cap to one with a marking of "120".........more PRESSURE........Ihave used Both on my car and they EACH function properly. I keep the "120" cap on the car as a matter of general practice........with the older one as a spare

..

Best wishes always and keep those diesels humming!
Spo out!

Fisherman · #8 05-29-2003, 05:25 PM

I blew my upper radiator hose mount off the radiator last month and drove back through the northern california moutnaitns with the cap inthe first indent and never even got warm. in fact, I'd swear it ran cooler than it di before but anyway. No problems at all.
I think I'd pop the cap to the first indent and watch the guage. It's gonna have to get pretty hot to cause you to have to tighten it down.
Unless you get the pedal to the metal and stay that way for a while like I did... I still say I was blowing away that Lexuas with my old non-turbo 300 when she blew!

rwthomas1 · #9 05-29-2003, 11:20 PM

Well after adding the (liquid) BarsLeaks and installing the 7psi cap and an uneventfull test drive to Krispy Kreme the morning after there was a nice large puddle o' coolant under the motor. Weep hole had coolant coming out of it so out came the waterpump. Replaced with a japanese pump that has a stamped steel impeller. I would like to have been choosey but I need the car and the price was right. The whole replacement was easy as waterpumps go except for those little 10mm bolts that hold the fan/clutch on. What son-of-an-unmarried-woman designed that setup? Just a little more room and you'd be able to use the box end of the wrench but no, you get to use the open end and round the little buggers off! Nothing a mini-sledge and cold chisel couldn't fix. Anyhoo, the new pump is in, no leaks so far. Still using the 7psi cap as I see no reason not to. Poured the old coolant back in so the BarsLeaks is still in there. Regarding running pressurized or not. I ran 260 miles with the cap loose and had no problems. Then I made one short 15minute trip and it blew some coolant out the tank. Wierd. The MB/617 uses a standard-size cap so you can get them at any parts store and in many different pressures. 7psi seems very reasonable considering that MB's new superceded cap is a 1.4bar and that is 20psi!!! 7psi is about 0.4bar. SPO, sorry I missed the gtg. See ya at the next one! Thanks for all the input guys! It helps to know someone else is thinking this stuff through with ya! RT

Thomaspin · #10 05-30-2003, 04:26 PM

Like this and you will be able to get at those fan bolts without rounding them.

rwthomas1 · #11 05-30-2003, 05:49 PM

Thomas,
Where the heck were you 2 days ago? Jeez, I tell ya some guys just like to rub it in! Seriously though, good idea. I started to round the heads off on two of 'em and then I got the mini-sledge and a cold chisel and gave 'em a good pop to loosen them up. They came out after that. RT