Carbon Monoxide in Cab

['68OrangeSunshine]

I think I'm getting some kind of exhaust leak in the cabin of my '71 Jimmy with double wall top. I'm pretty sure the headers and collectors are tight. Could the fumes be coming in from the tailgate or under the truck?
On cold days when it's all buttoned up, I get groggy. On long drives this is bad.

[cparman]

Where do the tailpipes exit? Yes it is possible to get fumes inside the cab from the rear of the truck. I have seen somewhere a rubber seal the sits inside of the cab, and seals the base of the tailgate. Do you have the side seals for the tailgate inplace? Maybe move the location of the tailpipes. Crawl under the truck and run your hands around each pipe with the engine running and double check for a leak.

Originally Posted by '68OrangeSunshine

I think I'm getting some kind of exhaust leak in the cabin of my '71 Jimmy with double wall top. I'm pretty sure the headers and collectors are tight. Could the fumes be coming in from the tailgate or under the truck?
On cold days when it's all buttoned up, I get groggy. On long drives this is bad.

[special-K]

Are your pipes straight out the back,by chance?If the tailgate and hatch aren`t sealed (were they ever?) fumes will roll up from the draft area behind the vehicle.I never had a Blazer that didn`t have pipes out the sides.Even then,fumes can find their way into the back of the Blazer.Mostly when it`s cold out because it`s warmer inside.This is why I like the soft tops.They seem better...ventilated.

[lakeroadster]

To expand on Special K's comments.. To help minimize exhaust in the truck run the tail pipes out the sides of the truck behind the rear tires, not straight out the back. This helps to get the fumes "into the wind" and away from the low pressure area right behind the truck.

[vtblazer]

Originally Posted by special-K

If the tailgate and hatch aren`t sealed (were they ever?) fumes will roll up from the draft area behind the vehicle.

Yes, they were more or less sealed up.

GM had weather stripping sealing up the bottom of the tail-gate (carpet strip), there was rubber up the sides (typically missing) and then there is the hatch seal that 'must have' the metal strip attached to the top of the tail-gate in order to function correctly.

Even with all these components in place and in good shape, some exhaust fumes will still weep in but at a managable level.

Tip: Opening a window only makes it worse, keep em closed so the air (exhaust) can't circulate.

[Firebirdjones]

I haven't noticed it with our current blazer, but our previous one did. It had the exhaust routed out the sides behind the back tires as well, and it didn't help.
Just have to seal the tailgate area as mentioned above.

Our current blazer has the factory small rubber strips around the tailgate, but I found that really wasn't enough, and after years of use they compress to the point that they don't conform anymore. It's such a skinny strip anyway that I don't think it serves much purpose
I went accross the bottom of our tailgate with sticky sided foam just below the factory rubber strip as an added precaution.
It must have done a better job of sealing because my wife and I noticed right away the truck was much quieter inside, without the exhuast rumble and road noise coming through the back.

If It's sealing out the noise then it must be keeping out the fumes as well. Doesn't put much faith in the factory skinny rubber strips (for me anyway) I'd like to see those rubber strips stick out about an inch or so,,,,and tailgates just aren't the tightest hinge design anyway, and have some play in them.
Just a thought.

[mr48chev]

You do need to have the exhaust exit out the sides behind the rear tires on these as others mentioned above. Make sure that the tip of the pipe gets out in the air stream too.

Just as the air flow sucks dirt, muck and road debris onto the tailgate and back window it can suck the exhaust right back up into the rig through leaking or missing gaskets.

The local muffler shops as a group won't install tailpipes going straight out the back of pickups with camper shells or any style of suv. Even if you don't run a shell on a pickup you have to request pipes straight out the back with the understanding you do not intend to run a shell.

[vtblazer]

Originally Posted by mr48chev

You do need to have the exhaust exit out the sides behind the rear tires on these as others mentioned above. Make sure that the tip of the pipe gets out in the air stream too.

This worked pretty well on mine:

[Firebirdjones]

Originally Posted by mr48chev

The local muffler shops as a group won't install tailpipes going straight out the back of pickups with camper shells or any style of suv. Even if you don't run a shell on a pickup you have to request pipes straight out the back with the understanding you do not intend to run a shell.

I've never heard that before. Sounds like the muffler shops are starting to get a bit extreme. I've always had my tailpipes out the sides, but it's never made a difference in getting fumes away from the cab.
I can drive with the back window popped open and the fumes are still overwhelming even with the tailpipes pointed out the side.

I honestly don't think there is much that can be done about it as far as tailpipe routing. There either has to be alot of ventalation or sealed up tighter than a drum.

[bouncytruck]

I've never had a problem with mine. You cannot see the exits looking at the truck from the side. I do have all the seals in place on the tail gate and hatch but I haven't had any issues running the soft top.

[snowblind]

ANY holes/cracks in your floor, doors, etc will let in fumes and having anything open (other than thee kick panel vents) will make it worse. Opening the rear hatch will make it MUCH worse.

I cut out out a bunch of the rear floors in my Jimmy and drove it a few days will plastic sheeting laid down. With all the windows closed the plastic lay flat but as soon as I cracked the window or even the vent window the plastic floated up two feet off the floor. The air outside the truck is rushing by so fast that when you crack a window it sucks the interior air out and replaces it with the turbulent air underneath and behind the vehicle.

[Dusty71blazer]

I have this issue too and I am working to fix it. One other thing to consider- How is it running? If your engine is running rich & making a stronger than normal exhaust smell that will make it even harder to resolve the problem..

['68OrangeSunshine]

Sorry I didn't mention that I have dual exhaust pipes exiting aft of the rear tires at an angle. There is no weatherstripping on the tailgate. I put new weatherstrip on the hatch when I replaced it with a new one from Brothers. A section on the right has come loose from the hatch, buit not enough to matter. I've always had this MOX problem. There is no seal berween the tailgate and the bed but the metel blazer strip is attached. An un- related problem is that the heater controls are unattached.
I did have a blowout in Mesa 3 years ago on the right rear tire. The steel belt flapped around and bent the right tailpipe. Could be related.
Thanks for the interest.

[special-K]

Originally Posted by vtblazer

Yes, they were more or less sealed up.

GM had weather stripping sealing up the ...

That`s what I was getting at,"more or less".When all is in order the wesatherstrip does a pretty good job.Even my`90 with pipes out behind the wheels had fumes roll in if the window wash open at all...worse with door window open.

['68OrangeSunshine]

I'm going to try a run of duct tape or similar on the tailgate hinge seal. And some foam wx strip on the tailgate sides.
I might as well have the windows open since the wx seals at the door window/top are shot too and blow in a lot.

['68OrangeSunshine]

I found a solution to the MOX problem. A strip of duct tape across the tailgate gap and some foam insulation left over from a window air conditioner clipped under the brackets on the sides of the tailgate. Not 100%, but tolerable.