W124 cooling system pressure - PeachParts Mercedes-Benz Forum

cele_997 · #1 10-20-2011, 08:04 PM

the vehicle: 1995 Merc E320. 159 000 miles.
issue: I am suspecting that my w124 is developing too much pressure in the cooling system. I have owned for four months and I have spent about $1000 on replacement parts for the cooling system.
1) when I bought car, it was mixing cold AC air in center vent with hot air on outer vents. Peachparts forum helped to figure out duo-valve issue. fixed
2) about a week after that it started mixing windshield washer fluid with coolant - i suppose the duo-valve was now actually working so coolant was now going thru the heater element in the windshield washer reservoir tank (maybe that's why the prev owner didn't change the duo valve..). I noticed the coolant level had shot up one morning - and then noticed that the windshield reservoir was empty - that and the fact that the coolant in the coolant overflow tank was now orangish-purplish - strange color. I replaced the heater element in the windshield reservior tank and that worked for all of two months and then same problem. I don't need heated windshield fluid in texas so I am planning on doing a by-pass job.
3) my overflow tank developed a crack and started leaking about two weeks after I had replaced the initial heating element in the windshield reservoir. I replaced the tank - suspected the high pressure issue back then and got a new reservoir cap. I fit rather tightly but then i thought that all new caps should fit tight - right???
4) the elbow joint that goes into the radio from the overflow line to the reservoir tank snapped - i just found it leaking during my morning fluid check. thanks the peachparts, i didn't have to buy the whole radiator - i replaced the elbow joint and that was that...or so i thought.
5) in a seemingly unrelated incident, my fan clutch bearing seized, the shaft heated up and snapped of and the fan went partying and met the main crankshaft pully - no radiator damage - or so i thought. I replaced fan clutch bearing housing, fan clutch, fan, fan belt
6) this week, i found a pool under my car in the morning, it was coolant. after a short drive, i pulled over and saw the leak coming from the radiator side - the same side on which the elbow joint goes - just a crack in the radiator side - so I am now looking at a radiator job.

my question to the forum is: is it possible that my cooling system is building up too much pressure and thus various components are now taking turns in failing. the engine never overheats, its starts right up, idles well so i don't think i have a blown head gasket pushing pressure into the cooling system. I have not replaced the water pump and from the slight wear on the bearing, I doubt that the waterpump has been replaced lately so I dont think its the case of a new water pump suddenly pushing pushing too much pressure on old components.
HELP! - what else can i check for? before i replace that radiator, I must find whatever is causing cooling system components to break. if i don't, the next thing to go will probably be the heater elements.
Any ideas will be appreciated

gmercoleza · #2 10-20-2011, 11:06 PM

Number one cause of severely elevated cooling system pressures is a blown headgasket. Check your coolant and oil to see if they are mixing.

cele_997 · #3 10-20-2011, 11:37 PM

Quote:

Originally Posted by gmercoleza

Number one cause of severely elevated cooling system pressures is a blown headgasket. Check your coolant and oil to see if they are mixing.

no mixing. i just did the fan clutch job 3 weeks ago and i drained all the coolant - no oil in coolant. I check my oil level every week - no coolant in oil.

i am thinking maybe there is a crack in the cylinder head. also, why wouldn't this pressure get relieved via the expansion tank cap - i thought that the cap valve would open once the pressure went over a given value.

all the same, are there any tests (other than checking for oil in coolant) that i can conduct - maybe i just happened to replace a defective reservoir cap with another defective reservoir cap.

I read in another thread that once one component of a system fails, it maybe an indicator that the other components of that same system are waiting in line to fail also - so i just happened to buy a car that had reached end of life for the cooling system component. At 159 000 miles - is this more or less expected behavior?

shiny star · #4 10-28-2011, 05:33 PM

Six months ago i had almost the same problem (water pump leaks): i have tested the caps (2, new)

Boths opens at the correct pressure of 1,4 bar (indicated on the cap).

For testing the cap with few tools (!):

With a cold engine disconnect the small tube from the radiator at the small input reservoir tank.

Connect one pump for tires with pressure gauge (such stanley) at the reservoir tank small input

Tight the small tube from radiator

Start pumping air in to the tank until the pressure gauge does not increase more.

The reading is the opening pressure of the cap.

Listening to the breathing tube of the reservoir cap, you feel the air out.

JohnM. · #5 10-28-2011, 05:58 PM

Quote:

Originally Posted by cele_997

I read in another thread that once one component of a system fails, it maybe an indicator that the other components of that same system are waiting in line to fail also - so i just happened to buy a car that had reached end of life for the cooling system component. At 159 000 miles - is this more or less expected behavior?

Most people have some combination of water pump / radiator / head gasket (because of radiator) issues by 100,000 miles. So the fact that you made it to 160,000 is above average. I bought my car with a bad radiator, bad headgasket, and replaced the water pump when I was in there @ 125,000.