Strange Noise/Smell

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TOME

TOME

Joined
Oct 20, 2008
Threads
50
Messages
304
Location
USA
Ocasionly when i start up my 60 i hear this po/hissing noise that sounds like it coming from under the passenger seat. After the noise the most terrible smell of my life fills the truck. it sux hard. There is nothing consistant about when it does it, only that it does it randomly.

All i can figure is that it could be something to do with the rear a/c.

Advice?
 
You have rear AC?!? Wow. But that's probably not it. There is a vent for the distributor cap that connects to a filter in the firewall behind the glove box. Check that the distributor cap ventilation system is working properly.
 
That's what it is...vacuum via the manifold and dizzy side vcv should be pulling that vapor out I believe, and it isn't. It is then igniting in the dizzy and expelling the spent exhaust through the breather vent below the glove box as it is currently doing in mine.
 
ok. what can i do to fix and is this a sign of bad things to come?
 
It seems mildy degenerative....did you desmog recently? I can't remember. I'm going through the same thing, mostly because I did my desmog incorrectly. ( I had routed the vacuum line in charge of clearing the vapor to atmosphere instead of vacuum) Once I routed it to the vacuum port on the manifold it lessened but did not cease so I am going to replace all my vacuum lines and my dizzy side vcv. I think the biggest danger is a detonation big enough to crack the dizzy cap and to a lesser degree, building up carbon where the cap and rotor meet.

Your situation may just be bad vacuum (for whatever reason) or a funky vcv.
 
No desmog at all. the noise is not a detonation or anything of that nature but more like a rapid release of a LOT of pressure
 
I have the same event happening. I thought it was coming from under the passenger seat also. Mine smells like a struck match. It happens at random. Sometimes I see a white puff of smoke. It happens at the exact moment I turn the key to the on position. I thought I had a short with the rear heater, checked all wiring..no issues.
 
TOME said:
No desmog at all. the noise is not a detonation or anything of that nature but more like a rapid release of a LOT of pressure
Click to expand...

Maybe detonation isn't the right word, more like ignition...it makes a WHOOOOFFFF sound under the glovebox (where the air vent for the dizzy is apparently) then a matchstrike smell like was said.
 
alpendubber said:
I have the same event happening. I thought it was coming from under the passenger seat also. Mine smells like a struck match. It happens at random. Sometimes I see a white puff of smoke. It happens at the exact moment I turn the key to the on position. I thought I had a short with the rear heater, checked all wiring..no issues.
Click to expand...

That is EXACTLY what it is!
 
Disconnect the hose from dissy cap to VCV. Leave dissy cap open. See if symptom goes away.
If explosion is gone, then problem is in VCV system.
If explosion persists, then there is another source of flammable gas in dissy.
 
FJ40Jim said:
Disconnect the hose from dissy cap to VCV. Leave dissy cap open. See if symptom goes away.
If explosion is gone, then problem is in VCV system.
If explosion persists, then there is another source of flammable gas in dissy.
Click to expand...

The noise is i random and occurs only on startup, so i dont thing this would work (i may b wrong tho)

2mbb said:
You have rear AC?!? Wow. But that's probably not it. There is a vent for the distributor cap that connects to a filter in the firewall behind the glove box. Check that the distributor cap ventilation system is working properly.
Click to expand...

is this the filter you were talking about? either way, its dirty and needs to be cleaned/replaced. any idea on how to get to it?
photo.webp
 
heater

What about burning coolant w/in rear heater circuit? Probably would not be burning at startup though, since nothing is hot enough to burn it....
 
I dont think thats it. Like alpendubber said, it only happens when the truck is started, and only then
 
TOME said:
The noise is i random and occurs only on startup, so i dont thing this would work (i may b wrong tho)
Click to expand...
Yes indeed, you would b wrong.

is this the filter you were talking about? either way, its dirty and needs to be cleaned/replaced. any idea on how to get to it?
Click to expand...
No, that is not a filter. It is just the foam covered recirc door for the HVAC.

The filter is a small round can that is screwed right to the firewall. Look underhood to see where the dissy vent hose attaches to the filter, then find the filter on the other side of the firewall.
 
well its just a wrong day then.

I have looked and didnt see anything like that. any chance of pics?
 
The filter is a small metal can w/ a wad of fiberglass stuffed in it. It is at the end of the large breather hose off the dissy cap.

It doesn't matter whether you can see the filter inside (it is behind the glove box, very difficult to see.)

The important thing is to diagnose the breather system to see if it is ventilating the cap properly.
The other thing to check is the vacuum advance canister to see if it is leaking.
 
alright. the problem is becoming more consistent so I will disconnect the hose and see if that fixes the problem. Is there any danger in leaving the hose to the VCV disconnected?
 
then ill give this a shot
 
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