Inflated upper radiator hose? M104 - PeachParts Mercedes-Benz Forum

juribe2 · #1 05-16-2007, 08:46 AM

Hi,

I replaced all radiator hoses (upper, lower, bypass) 6 moths ago. A couple of days ago, I noticed that when the engine is hot (90 - 100C), the upper radiatior hose gets inflated. I thougt that the system pressure was supposed to be absorved by the expansion tank and not by the hoses.

Do you think this is normal or should the hoses keep the same diameter when hot?

Almost forgot: I also replaced the expansion tank, the exp. tank cap and the termostat 6 months ago. The exp. tank look good but I think it is not releasing pressure as it is supposed to.

Thank you,

Juan

jlomon · #2 05-16-2007, 08:58 AM

I'll bet you've got air in the system somewhere, and it is finding the high point in the system, which is the upper radiator hose (which sits higher than your expansion tank on that car). I did the exact same thing with my C last summer, I had my indy replace every radiator hose under the hood. Before he sent me away he basically "burped" the system for me to make sure it didn't have air in the lines. You might have to get this done. I didn't pay close enough attention to see what he did, so I can't tell you. Maybe someone else here can offer some advice on that.

juribe2 · #3 05-17-2007, 07:59 AM

It's been 6 months since I replaced all this parts and the coolant. Does the air stay that long traped in the radiator? How can I remove the air from the system?

After filling the system, I did remove something like a drain plug on the thermostat housing thinking that that was the way to remove air from the system. During the first week I did have to add some coolant because of air getting out of the system. Now I don't know how to remove more air. Should I remove the upper hose from the radiator neck to let the air get out or something like that?

Yesterday I also noticed that there is a small leak starting somewhere near the upper neck of the radiatior. Is it possible that the inflated hose is the source of the leak or it is a sign of a radiator failure?

Thanks for you help guys.

Ferdman · #4 05-17-2007, 10:28 AM

Juan, remove the cap from the expansion tank (with the engine cold) and run the engine for 10 - 15 minutes ... that will allow air trapped in the cooling system to escape.

The upper hose connections on the Behr radiators become brittle with age, develop circumferential cracks and break off. You may want to remove the upper radiator hose and closely inspect to see if the hose connection is cracked. Some folks do a crude fix with a piece of copper inserted inside the hose connection ... better to replace the radiator and preclude having the connection break off at the most inopportune time and leaving you stranded.

juribe2 · #5 05-17-2007, 12:15 PM

Thanks Fred. I'll check that and will let you know what I find. I'm ordering a new radiator since it's the only part of the cooling system I haven't replaced recently (I think it's still the one installed at the factory) and the car is running a little hot under high load.

One question: should I also replace that upper hose. It is only 6 months old but I don't know if getting inflated under pressure is a sign of wear.

gmercoleza · #6 05-17-2007, 12:21 PM

Also check out the hose itself. I have seen instances where the clamp was overtightened causing a tear in the inner layer of the hose (most hoses are multilayer separated by fiber mesh). With the inner layer torn, the strength of the hose is compromised and it can expand like a balloon under pressure. The heat and pressure may have softened the hose over the last 6 months.

kiwi_bloke · #7 05-17-2007, 06:36 PM

I've seen a faulty radiator cap cause pipes to "suck in" - could this cause the opposite as well?

Ferdman · #8 05-18-2007, 07:46 AM

Juan, it would be a good idea to replace the upper hose. Buy an OEM hose.

lee polowczuk · #9 05-18-2007, 08:35 AM

[QUOTE=Ferdman;1508527]Juan, remove the cap from the expansion tank (with the engine cold) and run the engine for 10 - 15 minutes ... that will allow air trapped in the cooling system to escape.

I second ferdman on removing the cap and letting the engine run... you may want to squezze to top hose with the cap off, too... to let it burp.

i don't know if if would automatically be getting another radiator howerver...

take off the upper hose carefully...and look inside the plastic neck...in could easily be lined with an aluminum ring... that's the re-inforcer....

i was pleasantly surprised to find it on our w124's.... a sure sign of replacement.

juribe2 · #10 05-18-2007, 12:14 PM

Thank you all for you imputs.

Last night I ordered a new radiator and a new upper hose. Since it takes a couple of weeks to arrive to my country, I'll try what you suggest this weekend and let you know about the results.

Thank you guys. This forum is great. I think if this forum didn't exist, I probably would have sold this car already because MB service is very complicated here.