westslope Posted June 24, 2009 Share Posted June 24, 2009 (edited) The right (passenger) side exhaust manifolds were leaking. I had them fixed at White Rock Muffler (White Rock, BC). So far I'm very happy with the work; on the way, I learned a few things. The vehicle is a '93 XE 5-spd. At the beginning of the decade, both exhaust manifolds were "done". In late 2007, a mechanic tighted the bolts for me. This week, the passenger-side manifold was removed, planed and then replaced with new gaskets and new studs and nuts with two washers each. Studs on the driver-side were tightened. The mechanic removes sheered studs by arc-welding on another stud that has a hexagonal head. He showed me how one of the studs on the driver-side was much larger than the others and cautioned that if the driver-side manifold failed, that repairs could lead to engine block troubles. What I fear is that mechanic who "did" the exhaust manifolds roughly 7 years ago broke off a stud and simply left it in there, hence the unusual length of the visible stud. The mechanic showed me studs that he claimed were the originals. So much for replacing all the studs a few years ago..... This mechanic advised that I leave the heat shields off to improve air circulation over the exhaust manifolds. Elsewhere, I understand the jury is still out on that modification. Currently, the heat shields are off both right and left manifolds. The engine seems to be slightly quieter and seems to accelerate more smoothly out of low speeds. Fuel economy should improve. Presumably there is less carbon monoxide getting into the cab but I suppose that is not a significant risk, otherwise we would have heard of somebody suing Nissan for CO poisoning by now. My advice. If you are going to hire a professional to have the exhaust manifolds 'done', shop hard, be prepared to pay more if in doubt. Worst comes to worst, go to a dealership and pay C$100+/hr. Do not be pound wise and penny foolish like I was a few years back. Dealerships have much more experience with exhaust manifolds than small shops with high turnover rates..... BTW, there is a disconnected ground strap connected to one of the right-side manifold heat-shield bolt holes. Does anybody have any idea of the original purpose of this ground strap? Edited June 25, 2009 by westslope Link to comment Share on other sites More sharing options...
adamzan Posted June 24, 2009 Share Posted June 24, 2009 My ground strap is disconnected too, it doesn't seem to be affecting anything. I plan to fix it someday... The shop that did my studs left the passenger heat shield off because where it bolts on was rotted ( i didn't really care). The driver side one is still on though. I haven't noticed any heat differences, other than I now have to be VERY careful when changing the oil lol. Link to comment Share on other sites More sharing options...
orca4wd Posted June 25, 2009 Share Posted June 25, 2009 I think is a good idea to leave the heat shields off to improve air circulation. However, one concern is some of the rubber pieces such as oil sensor cover and rubber around the dipstick may melt due to the heat coming from the exhaust manifolds. After reading your article, I remove those shields, but left the lower passenger heat shield to prevent heat away from oil sensor area. I figure heat raise upward so that it should not affect the circulation. The carbon monoxide getting into cab should not be an issue in IMHO. People don't put heat shield around headers, figure it should applies to manifold too. Right?? Link to comment Share on other sites More sharing options...
nunya Posted June 25, 2009 Share Posted June 25, 2009 People don't put heat shield around headers, figure it should applies to manifold too. Right?? They do make that header wrap/tape stuff though which I understand is basicly a form of heat shield, but never heard of anybody using it Link to comment Share on other sites More sharing options...
westslope Posted June 25, 2009 Author Share Posted June 25, 2009 orca4wd, Only the heat shields placed above the manifolds were removed. The oil pressure sensor sits below the manifold, close enough to the oil filter, that, if a person isn't careful, oil can leak on to the oil ps during oil filter removal. The heat shields on the exhaust pipes were left in place. (BTW, in passing, I asked the mechanic to check the oil ps. He did and concluded that it was dry, i.e., not leaking fresh oil.) Link to comment Share on other sites More sharing options...
orca4wd Posted June 26, 2009 Share Posted June 26, 2009 (edited) Can anyone think of a negative aspect of leaving the heat shields off the manifold? Other than one can get burn while changing oil filter. Personally, I would wait till the engine cool down before attempt to change oil filter even with the heat shield in place. I am curious if the raising heat will harden the valve cover gaskets. It will probably take years befoe the heat will affect the valve cover gaskets. The overall reduce exhaust heat, thus, reduce the chance of having to replace boken studs may out weight it all. Any thoughts or advises.... please fire away! Edited June 26, 2009 by orca4wd Link to comment Share on other sites More sharing options...
Formerly_94PathyMan Posted June 26, 2009 Share Posted June 26, 2009 Can anyone think of a negative aspect of leaving the heat shields off the manifold? Other than one can get burn while changing oil filter. Personally, I would wait till the engine cool down before attempt to change oil filter even with the heat shield in place. I am curious if the raising heat will harden the valve cover gaskets. It will probably take years befoe the heat will affect the valve cover gaskets. The overall reduce exhaust heat, thus, reduce the chance of having to replace boken studs may out weight it all. Any thoughts or advises.... please fire away! Well, since there are wires near the area, they were probably put in for those reasons, but as long as you have things tucked away and secured, no, I cannot truly think of a huge negative impact. Higher engine bay temps? Other than that, you got me. Link to comment Share on other sites More sharing options...
pathynoob Posted June 26, 2009 Share Posted June 26, 2009 i was advised to try to use jb weld to seal my exhaust manifold leak. will jb weld work or should i try to go though all the hassle of replacing the exhaust manifold gaskets. from the look of it the exhaust manifold is rusted and has a good chance of some bolts breaking off. Link to comment Share on other sites More sharing options...
GrimGreg Posted June 26, 2009 Share Posted June 26, 2009 i was advised to try to use jb weld to seal my exhaust manifold leak. will jb weld work or should i try to go though all the hassle of replacing the exhaust manifold gaskets. from the look of it the exhaust manifold is rusted and has a good chance of some bolts breaking off. It will work......for no more than a minute, then it will just burn off. I tried to JB weld my Y-pipe for a trail fix, and it was fine until I ran it, as soon as it started to heat up, gone. Link to comment Share on other sites More sharing options...
orca4wd Posted July 3, 2009 Share Posted July 3, 2009 Today the weather hit in the high 90s. I did notice my Pathy runs quite smoothly with A/C blowing. I believe the engine has a little more get up and go feel with the removal of the heat shields. Just curious if other have this feeling? Now, I am plan to remove the heat shield out of my Honda Civic as these little engine need all the power it can get.... Well, since there are wires near the area, they were probably put in for those reasons, but as long as you have things tucked away and secured, no, I cannot truly think of a huge negative impact. Higher engine bay temps? Other than that, you got me. Link to comment Share on other sites More sharing options...
magregor Posted July 3, 2009 Share Posted July 3, 2009 Personally, I don't think removing the heat shield will help in performance, it will just allow the exhaust manifolds to dissipate heat better than a rusty ol' aluminum plate rattling around. When the heat shields are new, they perform well, but when they get older and lose their heat dissipating qualities and end up just causing grief... SO, before you go crazy yanking off the heat shields on your civic to help boost performance...you might want to reconsider the reason why you're going through all that effort to gain 0 HP... Link to comment Share on other sites More sharing options...
orca4wd Posted July 3, 2009 Share Posted July 3, 2009 Yeah, I don't disagree that will have zero HP gain with the heat shield removed. The vehichle engine just feel it has less resistance when coming off the line. Anyway, for what it worth the dissipate heat may improve the manifold studs from heat/cold expansion. Personally, I don't think removing the heat shield will help in performance, it will just allow the exhaust manifolds to dissipate heat better than a rusty ol' aluminum plate rattling around. When the heat shields are new, they perform well, but when they get older and lose their heat dissipating qualities and end up just causing grief... SO, before you go crazy yanking off the heat shields on your civic to help boost performance...you might want to reconsider the reason why you're going through all that effort to gain 0 HP... Link to comment Share on other sites More sharing options...
Precise1 Posted July 3, 2009 Share Posted July 3, 2009 it will just allow the exhaust manifolds to dissipate heat better than a rusty ol' aluminum plate rattling around. Rusty Aluminum?? This I would like to see... Anyway, for what it worth the dissipate heat may improve the manifold studs from heat/cold expansion. They will still get as hot as the exhaust gasses+engine bay temp allow and as cold as ambient temp when you park it. I'm guessing zero difference. I believe the engine has a little more get up and go feel with the removal of the heat shields. I think your butt dyno needs calibrating... B Link to comment Share on other sites More sharing options...
magregor Posted July 3, 2009 Share Posted July 3, 2009 Rusty Aluminum?? This I would like to see... Sorry "Oxidize" to be grammatically correct Link to comment Share on other sites More sharing options...
unccpathfinder Posted July 3, 2009 Share Posted July 3, 2009 Rusty Aluminum?? This I would like to see... wink.gif take a steel wire brush to some aluminum and then let it sit in a nasty environment...granted the aluminum still isn't rusting but it makes "rusty aluminum" Link to comment Share on other sites More sharing options...
Jeffrey Posted July 4, 2009 Share Posted July 4, 2009 Hello to all, I'm a newb to this site and I was reading about this exhaust manifold repair. I have my rig in the shop now getting the passenger side manifold replaced with a Dorman brand replacement. My 1st question is has anyone had a bad experience with Dorman manifolds in regards to failure/cracking and my 2nd question would be will I see a little better throttle response from 25-35 mph? Link to comment Share on other sites More sharing options...
Precise1 Posted July 4, 2009 Share Posted July 4, 2009 I do not know of Dorman, is this an OE type replacement? If so, I doubt there will be any gains. How much does it cost? It may be worth upgrading to headers... B Link to comment Share on other sites More sharing options...
ditchdiggerjcf Posted July 4, 2009 Share Posted July 4, 2009 I do not know of Dorman, is this an OE type replacement? If so, I doubt there will be any gains. How much does it cost? It may be worth upgrading to headers... B I was told that if you removed the catalytic converter, and installed a good free flow exhaust that it reduces the heat and backpressure on the exhaust manifolds, which keeps them from cracking. Any thoughts on this? Link to comment Share on other sites More sharing options...
Precise1 Posted July 4, 2009 Share Posted July 4, 2009 Well, cat back systems do make a difference. I had a Magnaflow on my old 95 with the stock cat and exhaust manifolds. There are high flow cats that do a good job, and only a jerk removes the cat entirely. B Link to comment Share on other sites More sharing options...
ditchdiggerjcf Posted July 4, 2009 Share Posted July 4, 2009 Well, cat back systems do make a difference. I had a Magnaflow on my old 95 with the stock cat and exhaust manifolds. There are high flow cats that do a good job, and only a jerk removes the cat entirely. B Sorry, the only way I hug a tree is between the bucket and thumb on the trackhoe as I pick it up to throw it on the fire. I really don't think removing a cat is a big deal Link to comment Share on other sites More sharing options...
Jeffrey Posted July 4, 2009 Share Posted July 4, 2009 I do not know of Dorman, is this an OE type replacement? If so, I doubt there will be any gains. How much does it cost? It may be worth upgrading to headers... B Yes Dorman is an OE replacement, Believe it or not I picked up the manifold,gasket, and all other parts for replacement for $97.50 tax and shipping included. I thought about headers, however I've got two other cars to feed and my pathy is just my daily driver. I'll probably end up going with a magnaflow hi flow cat to a flowmaster 50 series muffler. Link to comment Share on other sites More sharing options...
Precise1 Posted July 5, 2009 Share Posted July 5, 2009 Sorry, the only way I hug a tree is between the bucket and thumb on the trackhoe as I pick it up to throw it on the fire. I really don't think removing a cat is a big deal Yeah, ok... I do not know of Dorman, is this an OE type replacement? If so, I doubt there will be any gains. How much does it cost? It may be worth upgrading to headers... B Yes Dorman is an OE replacement, Believe it or not I picked up the manifold,gasket, and all other parts for replacement for $97.50 tax and shipping included. I thought about headers, however I've got two other cars to feed and my pathy is just my daily driver. I'll probably end up going with a magnaflow hi flow cat to a flowmaster 50 series muffler. I hear you about cost justification; no you couldn't get headers for less than 150% of that at best. There are many threads, some quite recent, about exhaust and one with a video clip of the sound of the FM-50 IIRC. I like the magnaflow muffler myself, but there are many good brands. You just have to research and pick... B Link to comment Share on other sites More sharing options...
Jeffrey Posted July 8, 2009 Share Posted July 8, 2009 I just had my new manifold installed and man, what a difference that makes. For some reason my rig had a problem when accelerating from 25-35 mph. It would shudder and just basically have a hard time. Now after the repair it seems to be performing better, I hope that freeing up the rest of the exhaust with a high flow cat back system will improve performance as well. Link to comment Share on other sites More sharing options...
Alkorahil Posted July 11, 2009 Share Posted July 11, 2009 take a steel wire brush to some aluminum and then let it sit in a nasty environment...granted the aluminum still isn't rusting but it makes "rusty aluminum" Aluminum corrodes but it does not rust. Rust refers only to iron and steel corrosion. Aluminum is actually very prone to corrosion. However, aluminum corrosion is aluminum oxide, a very hard material that actually protects the aluminum from further corrosion. Aluminum oxide corrosion also looks a lot more like aluminum, so it isn't as easy to notice as rusted iron. When iron corrodes the color changes and it actually expands. This expanding and color change can produce large red flakes that we all know as rust. Unlike aluminum oxide, the expanding and flaking off of rust exposes new metal to further rusting. Link to comment Share on other sites More sharing options...
CO94LEV6 Posted July 14, 2009 Share Posted July 14, 2009 Can anyone think of a negative aspect of leaving the heat shields off the manifold? Other than one can get burn while changing oil filter. Personally, I would wait till the engine cool down before attempt to change oil filter even with the heat shield in place. I am curious if the raising heat will harden the valve cover gaskets. It will probably take years befoe the heat will affect the valve cover gaskets. The overall reduce exhaust heat, thus, reduce the chance of having to replace boken studs may out weight it all. Any thoughts or advises.... please fire away! To improve performance think cold air in and hot air out. Removing the manifold covers increases the air temp under the hood and if you are pulling this hot air into the air intake than you will lose power. A modification of adding cold air intake helps to bypass this problem. You also see cars with thermal spacers that stop the transfer of conductive heat from the engine to the intake manifold. A hot intake manifold also heats up the incoming air and you loose power. On the exhaust side you want to keep the exhaust hot to keep the velocity up as it exits the tailpipe. As the exhaust cools, it expands and slows velocity and increases backpressure reducing power. Thus the header tape that someone mentioned earlier. The problem with header tape is that it can hold moisture against the header and cause premature corrosion to the pipes. My last car project car was a turbo and that's why intercoolers are installed to reduce the temp of the air going into the engine. BTW having one side with a manifold cover on and the other side without is theoretically a very bad idea. Exhaust systems are designed for a venturi effect. Meaning the timing of the exhaust pulses out of the engine are timed and actually assist in pulling exhaust gases out of the cylinders as the engine fires. Uneven cooling of the exhaust gasses on both sides of the engine could upset this timing. This is generic engine performance theory, I haven't messed with my pathfinder enough to see what (if any) difference it makes to our engines, but on some engines the difference is noticeable. I personally have ceramic coated pacesetter headers that seem to work fine. I've had them for about 5 years so I can't really remember what it was like before with the stock manifold. I do remember that the headers did not fit properly and the installer had to customize the fit. Welding coated headers is not fun. He had to grind off the ceramic coating at the area of the welds. One benifit that nobody has mentioned is that the aftermarket headers are significantly lighter that the stock manifolds. The lighter the vehicle the less power it takes to get you moving. Link to comment Share on other sites More sharing options...
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