|
|
|
#1
|
|||
|
|||
How to tell tank vent tube is blocked?
It seems that every time I open the 'diesel' cap to the tank I hear an inrush of air. What is causing that, a blocked vent tube? If I do nothing, would the tank collapse due to vacuum when I run the tank dry/very low?
Your advice is appreciated.
__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed. W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html 1 X 2006 CDI 1 x 87 300SDL 1 x 87 300D 1 x 87 300TDT wagon 1 x 83 300D 1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry. Last edited by ah-kay; 12-01-2009 at 08:24 PM. Reason: typo |
#2
|
||||
|
||||
Quote:
I've actually seen a picture on here of a guy who had his tank collapse in on itself with the vacuum. I'm not sure who it was, but it looked crazy. Definitely get it unblocked.
__________________
-Typos courtesy of my mobile phone. |
#3
|
||||
|
||||
The vent valve on the 124 is designed to hold a certain amount of Vacuum or pressure, i have looked it up before for a similar question,dont have the cd at hand right now.At least for that model the vent is not open to atmosphere,yours may be the same or not. Found it,normal operation pressure up to 50mb or vacuum of 1 to 16mb.the pressure relief control is in the fuel cap,the vacuum control is accomplished by the vent valve.Don
__________________
Red Green "This is only temporary,Unless it works!" 97 E300D 157000 miles 87 300TD ?141k? miles Last edited by oldiesel; 12-01-2009 at 08:56 PM. Reason: more info |
#4
|
|||
|
|||
It is not possible to draw that conclusion on the basis on the information presented.
|
#5
|
||||
|
||||
I have the same symptoms, even though I recently cleaned the tank very thoroughly. I believe I blew into the vent tube and I verified that the air was passing thorugh although slowly - I thought that was because of the small tube diameter. Anyway, even though the air could pass through it I still get some rush as I open the fuel cap... hmmm - I'll be watching this thread as well...
__________________
1987 Mercedes 300SDL; SOLD 1985 Mercedes 300D; SOLD 2006 Honda Pilot - wife's ride; 122K; 1995 Toyota Land Cruiser - 3X locked; 182K |
#6
|
||||
|
||||
Are you sure it is vacuum pulling air in, or is it pressure pushing air out? The only reason I ask is because my '95 does the same thing, for a long time I thought it was sucking air in, that is, until it got worse and I could feel it blowing the fuel cap off when I twisted it to remove it. Also, the pressure began pushing fuel past the cap. Anyway, it could be either and sometimes it is difficult to tell.
__________________
'95 E300D ("Tank") - 231,000 miles '79 240D ("Biscuit") - 197,250 miles (Sold) '83 240D ("Ding-Ding") - 217,000 miles (Death by deer) ______________________________________ "Back off, man. I’m a scientist” ~ Peter Venkman |
#7
|
|||
|
|||
I really do not know whether it is sucking air in or pushing warm air out but it seems to be happening in the SDLs and 300D. If the vent tube is OK then the tank should be at atmospheric pressure, there should be no hissing sound. Am I correct?
There are 2 ways I can try: 1) Connect compressed air into the tank from the fuel line and see it stays pressurized - It would not pressurize if the vent tube is OK. 2) Get spare cap, drill a hole, hook it up a MityVac and drive the car around. If it shows a vacuum then the tube is blocked. Would any of these 2 methods work?
__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed. W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html 1 X 2006 CDI 1 x 87 300SDL 1 x 87 300D 1 x 87 300TDT wagon 1 x 83 300D 1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry. Last edited by ah-kay; 12-02-2009 at 02:14 AM. Reason: typo |
#8
|
||||
|
||||
On the '83 anyway, run a stiff wire up through the vent cap, see if there is any obstruction.
__________________
83 SD 84 CD |
#9
|
||||
|
||||
Quote:
What other suggestions do you feel can help?
__________________
-Typos courtesy of my mobile phone. |
#10
|
|||
|
|||
Quote:
Quote:
|
#11
|
||||
|
||||
Quote:
I waited until the next time and let the car sit an hour. Still a hiss so I did the wire method and I guess I pushed the sludge back into the tank since I don't have any suction when I remove the fuel cap.
__________________
-Typos courtesy of my mobile phone. |
Bookmarks |
|
|