Loud Hissing

[togles]

Was driving on the freeway last Sunday, started up an incline and noticed the truck was moving all of the sudden slowly. I hit the gas and downshifted the transmission and the rpms went up as expected but then the truck died and wouldnt start thereafter. I had it towed home and later found that the coil wire was missing from the distributer. I hooked it back up and was back in business or so I thought. Now when i drive it there is a really loud hissing noise and the truck has like no power. No leaks anywhere but there is a faint hint of coolant smell. Temp gauge looks ok too. I have 263k miles, purchased with 262k. A friend suggested I do a compression test on it which i plan on doing. I did a test earlier with soapy water and a blower in the tail pipe and I definitely have a leaky downpipe off the manifold and on a couple of weld points on the cats. I dont think this exhaust leak is causing this extreme hissing and loss of power though. Other than a compression test does anyone have any suggestions?

 

[robnicko]

maybe the Cat is collapsed and blocked? does it start at all?

 

[togles]

It starts right up and drives. Just hisses and has no power.

 

[G-Cat]

Hissing with the smell of coolant could be a pinhole. Check the hoses running through the firewall to the heater core.

 

[togles]

Hissing with the smell of coolant could be a pinhole. Check the hoses running through the firewall to the heater core.

Both front and rear heater cores are bypassed.

 

[togles]

I figured out the hissing issue. The vacuum hose that comes out of the bottom of the EGR valve and connects to the bottom port of the EGR vacuum modulator was disconnected from the EGR output. I slide the hose on and took it for a drive, it shot it right off. This btw, was not a hose that I replaced when I initially repaired my EGR system when purchasing the truck recently, I should have I suppose but it seemed unblocked and secured, albeit with no clamps of any kind. I just replaced it and used clamps, and took it for a drive. The hissing issue is resolved now but the truck is still running like crap, it has NO power whatsoever. I cannot get it to go above 30 mph up a hill with the gas pedal on the floor. It seems like its really struggling.

 

[togles]

Found this, and think its helpful. Maybe my cats are bad?

P

Thread 'EGR hose blows off - plugged catalytic convertors?'

Jan 10, 2013

While running some errands on the weeked, while getting on the off ramp getting off the freeway, heard a hissing sound startup under the hood near the firewall accompanied by slight loss in power. Pulled over and found the vac hose that connect to the lower port of the EGR to the EGR Vacuum Modulator had come off and was venting exhaust gas!

After cooling down, put it back on to get home and it did it again on the offramp nr home. No CEL codes thrown during either time.

I started ging thru the OEM manual and my notes on the last time i replaced the EGR, Modulator and VSV -- was...

• Phil H
• Replies: 25
• Forum: 80-Series Tech

 

[robnicko]

stand behind it at the tailpipe & have someone give it a rev it in neutral, if not much exhaust is felt coming out the tailpipe then theres a blockage.
remember engines are just a big pump and if they cant exhaust then it wont make power and the pressure will try & exit elsewhere.......HG.

 

[LongDuck]

Might also try tapping the Cats with a rubber mallet (*tapping, not hammering) to see if you hear excessive rattling. On most cars, when they go out, they disintegrate from the front, allowing the ceramic grid dust to clog the grid further downstream. That ceramic dust can be heard inside the car canister rattling around.

Or, disconnect the exhaust manifold pipe leading into the Cats and jam a wrench handle in there to create a gap, which would allow the engine to exhale better as a test at idle. Wear gloves removing the wrench!

 

[togles]

stand behind it at the tailpipe & have someone give it a rev it in neutral, if not much exhaust is felt coming out the tailpipe then theres a blockage.
remember engines are just a big pump and if they cant exhaust then it wont make power and the pressure will try & exit elsewhere.......HG.

Good flow coming out of the tailpipe at idle and with revs.

 

[togles]

Might also try tapping the Cats with a rubber mallet (*tapping, not hammering) to see if you hear excessive rattling. On most cars, when they go out, they disintegrate from the front, allowing the ceramic grid dust to clog the grid further downstream. That ceramic dust can be heard inside the car canister rattling around.

Or, disconnect the exhaust manifold pipe leading into the Cats and jam a wrench handle in there to create a gap, which would allow the engine to exhale better as a test at idle. Wear gloves removing the wrench!

Definitely some rattling happening, more on the primary cat than the secondary one.

Can you please explain more about what you mean by jamming a wrench handle in the cat to create a gap?

 

[LongDuck]

Sorry, I should have been more descriptive; basically, unbolt the forward Cat from the exhaust manifold Y-connection, and when you remove the nuts holding them together, use a screwdriver as a shim to create a gap between the manifold and the first Cat. Get th gap wider by sliding the handle of a socket wrench into that gap, with the idea that you're creating an exhaust path to atmosphere BEFORE the Cats to test if the Cats are the restriction.

This is a field expedient method just as a test for short idle and maybe a few quick revs to see if the power improves. DO NOT drive around with it like this - just use it to test where the restriction may be coming from.

It's going to be LOUD so get some ear muffs and warn the wife-unit,

 

[efjayatee]

Sounds like a clogged cats.

 

[togles]

I spent all day yesterday removing the system end to end. With the cats making a noise when hitting with the rubber hammer, as much as I did not want to go down this path I ripped everything out. I just didnt believe that it could be the cats considering my truck passed a CA smog a month ago(After and extensive EGR repair, consisting of Modulator, VSV and all Vacuum lines - First and Second Day of Ownership - P0401 - https://forum.ih8mud.com/threads/first-and-second-day-of-ownership-p0401.1381187/). I new the cats were welded in s***ily and had leaks at all the weld points, and I had leaks at the manifolds and downpipe connectors as well, so I wanted to fix all that anyways and ordered all the gaskets, bolts and nuts for that job yesterday morning from Toyota.

Anyways, check it out. The primary cat was completely open, with a few pieces of debris in there which shook right out. The secondary cat was completely clogged, it was like concrete and I am not exaggerating, I could not chisel it out with a big screwdriver, not that I put a whole lot of effort into it, but it was HARD packed like concrete.

New Magnaflow downpipe / cat on order. Cleaning up broken studs on the manifold downpipe connectors, hoping to reuse those. Still perplexed as to how this thing passed smog a month ago. I am seriously considering only running the 1 cat moving forward and not 2. I think this way it might be less likely to clog a second one when it fails the next time.

Primary Cat off the downpipe -

Secondary Cat -

Primary Cat - Shook the garbage out

Secondary Cat - Out to Muffler

 

[efjayatee]

I replaced mine with non CA-CARB Walker and passed smog visually and state on our 96 LX450.

 

[togles]

I replaced mine with non CA-CARB Walker and passed smog visually and state on our 96 LX450.

How did you acquire the Walker unit? All the sites wont ship to CA?

 

[efjayatee]

Shipped it to NV

 

[togles]

Nice to have that option

 

[efjayatee]

If you want it bad, you will find a way......hence my 93 obd1 Turbo

 

[togles]

Anything else that I should do, "while im in there" with all of this access? I know thats the oil cooler right there but is there anything I should do with it or anything else on this side?