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Exhaust Leak


Well-Known Member
November 11, 2013
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City, State
Year, Model & Trim Level
1993 Explorer Sport-4WD
My 93 Ex has an exhaust leak. I can smell it after stopping (engine off) , and hear something coming from the pass side of the engine (at higher speeds or accelerating). I took it to an exhaust shop and the owner said it sounds like it is coming from the pass exh manifold. He used a piece of hose. He could also smell it. He recommended tightening the exh manifold bolts, so I did - moved them maybe 30-60 deg. However, no change in smell (when I stopped) or noise at high speed or accelerating. Brief background, I did a head gasket job this past summer and when I put the exh manifolds back on, I used the exh manifold gaskets that came with the engine gasket kit. Also, when the heads were machined they only machined the head to engine surface, not the mating surface to the exh manifold.

I understand there is a exhaust test you can do using Sea Foam. Is there a thread that shows a step by step how to or can somebody explain it ? Please identify the how and where please - I am somewhat a newbie here. The exh manifold maybe cracked - I don't know. Need help. Thanks !

Ok - After reviewing the internet - I have found a simple way to test vehicles for leaking exhaust without having to use SeaFoam. I have read that it is possible to create engine seal leaks using SeaFoam that were not found before. So, this alternative method may be safer. I would appreciate any comments or suggestions if the method below is harmful to the engine.

So here is what I found by just using your shop vac or household vacuum cleaner as a blower and hooking it up to your exhaust - PLEASE NOTE IT IS BETTER TO DO THIS WITH A HELPER SO AS NOT TO BURN UP YOUR VAC MOTOR:

1. Move the vac hose on the vacuum to the port where air blows out
2. Duct tape the other end of the vac hose to your tail pipe. Make sure of a tight seal.
3. Jack up the front end of the vehicle and remove the tires and fender liners
4. Using a spray bottle with very soapy water, spray around exh pipe section and only do a small part of your exhaust system at a time, ie the pipe in sections, the Y pipe connections and then the exhaust manifold. Your helper will only turn on the vac when you have finished spraying a section and watching for bubbles (believe me you will see them). Or if you are by yourself, you can do this also - but it can be more difficult running back and forth. You can also use your hand to feel for rushing air. Again, you will definitely feel it.

5. After locating the areas of bubbling or feeling for air you can then do the necessary repairs.

Last summer I replaced the head gaskets and had the heads machined. I replaced top part of the engine gaskets including the exhaust manifold gaskets from a set I bought from the shop that machined the heads. They were Victor Reinz. I also replaced the 10 mm head exh manifold bolts with 13 mm head bolts. What I should have done was after carefully torqueing the bolts in a cross sequence was to warm the engine up and re-torqueing. Well, it developed a leak and took it to the shop machined in my first post. He recommended re-torqueing them with a warm engine, but that did not work. So, I replaced the exh manifold gaskets with Felpros and then did a re-torque after running the engine and getting it warmed up.

The noise, smell and vibration issue has now stopped. It was all related to the the exhaust manifolds. I will leave the fender liners off, and check the torque again tomorrow. When I did the bubble test above I found that now only were the passenger exh manifolds leaking (where the noise and vibration was coming from), but that the drivers side exh manifolds were leaking profusely as well. This is why I was smelling exhaust when I stopped the vehicle.

I hope this helps somebody out. Again, any suggestions or cautions are welcomed. Thank you.

So, in your opinion, had you simply re-torqued the first time after warming up the engine, you think all would have been fine?

I have a Victor headset I'm planning on using for my 94. I'd like to do the exhaust gaskets once.

Also, what screws did you use for the exhaust manifolds? Specifically the top. I'd though about running studs in them so that the stud would always stay in place, then just use a nut against the manifold.

To answer your first question - possibly, I don't know how good the Victor Reinz exh manifold gaskets are. I tried to re-tighten but was not successful. I did use Victor Reinz head gaskets and so far so good.

Concerning the exh manifold bolts. I went to Fastenal and they did not have direct replacement bolts for the exh manifold when I did the heads last summer. The original bolts for the exh manifold require a 10mm socket. Fastenal only could get bolts (same length-same thread) that required a 13 mm socket. Please remember that each manifold has two places that require shorter bolt lengths. So, for each manifold you have 4 longer bolts and 2 shorter bolts. Your idea to use studs and then nuts to attain clamp load sounds good, but I don't know if I would use them in this application due to the heat/temp. I can't really advise on this - maybe someone else may chime in. But, yes, definitley do a re-torque with the manifolds very warm and following the fastener torque specs.