vacuum leak ???

[Gitzit2]

i have read Turdle's VERY informative post about locating the vacuum canister on the gen 2 vehicles.
i have not been able to locate it in my 2007 XLT.
checked under the fenderwells and all around under the hood but can not locate it.

i believe that i am havng a similar problem with the canister since all works fine except when accelerating under a load i loose my vent air and it goes to defrost.
i am getting no hissing sounds and the a/c control work fine under all other conditions.

thanks in advance for your help!


Mark

 

[mace_b]

Same problem

I have the same problem you described. Is the canister the problem. Or should I look at a valve sticking because i hear hissing under the dash, there was mention of this in another post. Any one have any ideas?

 

[Gitzit2]

i do not get the hissing sound that i believe would indicte a straight vacuum leak...probably in the passenger compartment.

my issue is that i appear to loose vacuum when engine operating conditions are such that it does not produce as much vacuum....ie under load up a long hill when towing, etc.
i believe that my problem is with my vacuum resivour (sp) but i can not find it under the hood.

 

[mace_b]

The hissing wasn't all the time. so i went to the check valve took it off and blew throught it a few times put it back on havn't the vent problem for a couple of days. hopefully that fixed it.

 

[Gitzit2]

mace....
hope it solves your problem

 

[Gitzit2]

btt

any help woould be much appreciate!

 

[mr2fix2it]

you have to look for a leak in vacuum system it could be supply or it could be in the dash check all functions to make sure they work correctly max a/c, a/c,vent ,floor/defrost,defrost a common thing is max a/c door gets knocked off under pass side of dash the storage bottle is there also look for hoses off

 

[mace_b]

It started up again My next step is to replace the check valve as soon as i can get to the dealer and pick one up. Gitzit2 my canister is under the dash right by the passengers feet. (2008 explorer XLT) Have you replaced that check valve yet?

 

[Gitzit2]

thanks for the replies!!!!

i have not been able to find any obvious leaks so i was thinking that it was a vacuum capacity issue and targeted the vacuum reservior ball...but couldn't find it
i was looking under the hood

i'll look for and check the ball under the dash to see if it has water in it but the check valve would certainly seem like a possible cause, too.

is the check valve near the canister under the dash, too?

thanks again...you've been a big help

 

[mace_b]

The check valve on my vehicle is under the hood passanger side up high right up against the firewall about 1 1/2 inch long white and black. I pulled mine off again it was sticking open so i sprayed a little spray silicone in it working good now. ordered a new one at the dealer 13.00 dollars.

 

[Gitzit2]

i located and pulled the "ball" from under the dash and found it to be empty with all connections apparently tight

thanks for the tip on finding the check valve

i pulled it, too, blew air in one end and it flowed freely.

when i blew in the other end i expected it to seal completely but it did not.....some air still went through....not as much as the first direction but it certainly did not seal

i sprayed silicone as you did and now it seals nicely.

we'll test drive it this weekend and give a report

many thanks, mace_b!!!!!

 

[Gitzit2]

found the leak to be on the temp knob on the hvac controls
very small leak in cooling but when weather changed and needed heat the leak was very obvious
ended up taking to dealer
the fix was a new HVAC console

thanks for all the replies

 

[HoustonTexan]

I have a 2010 with the air conditioning going off under load. I hear the hiss then a thump that sounds like it is from the passenger side. Where is this check valve? I dont see it under the dash. Any pics? I am sure it is a vacuum leak but dont know where!

 

[GB1977]

Houston,
I'm having the same problem. Hoping someone chimes in with more information.