1994 C280 Expansion Tank Leak

[stargazer474]

Hi all ,

I was just wondering if anyone here has ever had there expansion tank leak on there car? and cause it to over heat?, i have had this overheating problem for some time now and alot of people were telling me it is a blown head gasket but i truely do not think that is what the problem is , because i do not have any oil mixed with my coolant or vise versa. and the engine runs excelent , the problems i am having are the car runs outta coolant quickly and or wont hold coolant which is making the car over heat extreamlyyyyyyy BAD.. well this morning we went out and started the car after letting it set for a while and dry and as soon as we started it up it shot some coolant out from around the expansion tank lid and then about 5 minutes later i see a stream of coolant commin from under the car and we look under it and it is leaking very badly a steady stream of coolant is comming from under where the expansion tank sets. so we are thinkin we will have to replace the Expansion tank and lid. hopfully this will solve my problem with the car over heating , it has a small oil leak but the oil leak looks as if it is comming from the oil pan (im thinking a Gasket)... anywas let me know if anyone else has had a simmular problem like this and if they changed there expansion tanks and lid and if it solved the over heating problem , thanks a bunch!!!!

Stargazer

[irieite]

If you take the cap off of the expansion tank to relieve the pressure and then reinstall the cap, start the car and pressure builds immediately in the cooling system, (evident by squeezing the hoses) you have a head gasket that is leaking combustion chamber gasses into the cooling system.

If this is not the case, a new expansion tank can be had for less than fiddy buck.

[stargazer474]

thanks for the reply,

earlier when we were checking for water leaks it seemd that the expansion tank was not even lettin it build the right pressure. so if a blown head gasket makes it build pressure from get go then theres another reason why i dont think its a head gasket .. and yea i have been pricing the Expansion tanks and theyy range from 30 to 50 bucks... im just keeping my fingers crossed that the expansion tank is the reason for my over heating probs

Stargazer

[martattack]

That could very well be the problem. It makes sense because pressure is needed to raise the boiling point of the coolant mixture. Leak cap = low pressure which lets the car get much hotter.

[Monster]

hey i got a 2000 c230k. over heated about 2 weeks ago. sent it in cuz it turned it self off and wouldn't start a few days after the over heating. they found a bad head gasket. like leaks in cylinders 2 & 4 i think, i dono. but they replaced that and my thermostat. and i must say with the new gasket the car runs 100% better. the super charger kicks in sooner and it seems to have a better low end to it. but any ways thats what just happened to me so i wouldn't be surprised.

John

[stargazer474]

Well the expansion tank has been replaced , when we took it off and got it out of the car we filled it up with water to see if we could find exactly where the leak was comming from we tracked it down to the tank itself finally , well low and behold the tank had a hairline crack in the bottom of it, it wasnt leaking from the tank at this time because well it had no pressure built up for it to leak from but it did have a few drops comming from the crack , soooo , we installed the new tank and hooked the hoses up and NO LEAKS!!!!!!!!!! WOOOHOOOO... now the next question is one of the small hoses on the top of the expansion tank torge the back of it is very brittle and needs replaced also does anyone know the right name for this hose. its not the one that goes to the radiator from the front of the tank its the hose that torge the back on the tank.. if anyone knows the name of this hose pleaseeeeee let me know fast thanks!!!!!!! .... oh yea the real test to see if it stopped the over heating problem will be tommorrow!!!! WISH ME LUCK!!!!!!!!!!

stargazer474

[martattack]

It's the hose that goes from the expansion tank to the overflow reservoir. You can really use any rubber coolant hose of the same diameter for it. It is 83cm long. If you really want the MB part number, it is 114 997 18 82.

[stargazer474]

In the process of Fixing the hose and running it up threw the fender well and back to the expansion tank i bumped what looks to be a bunch of vacuum lines and snapped one of them , i believe it is the intake manifold vacuum or something of that sort that has to do with the intake manifold, is this an important vacuum line and what does it effect if it is broken? i have the little tip that is broken and has to be replaced and snapped back into place i just cannot find on any website the little nipple tip thing i need for the vaccum line.

stargazer