My exhaust manifold just won’t seal up. I’ve been testing for leaks with the engine off by using a vacuum blower pushing air into the tailpipe, and then spraying the exhaust with soapy water and checking for bubbles. I see bubbles all along the top of the manifold and along the bottom on the spots where I am able to spray the soapy water. It's a new manifold, a Dorman, had to replace the old because it was cracked. Should I just keep tightening the nuts on the manifold studs? The book says 16 to 19 ft. lbs but that doesn’t seem very tight. I tightened them to 22 last night just to see if it made any difference but still no seal. My only guess as to why this is happening is that the studs/nuts are not applying enough pressure to crush the gasket and air is pushing past. So is the only solution to tighten further? Or is there danger that as the metals expand at different rates it could cause more issues? Beyond tightening it more, the only other thing I can think of would be using copper rtv to seal it, but I’m not sure how well that would hold up long term. I did recently install a remanned cylinder head, but given that the leaks are basically around the entire manifold I don’t think head warpage at the manifold mating surface would be the issue, and I did check the manifold itself for flatness and it was fine up to .004 of an inch. Any advice would be great. I’ve had the exhaust apart 4 times and this problem is killing me. I can smell fumes in the cabin while I’m driving and I get a check engine light code 172 running lean. Car is 93’ 1.9 liter.
I have used the Permatex Rred high-temp RTV on the joint between the output end of the catalytic converter and the intermediate pipe. It seems to hold up pretty well - doesnt char or blow away. I would think that joint would get as hot as the one between the head and the manifold. I have several 2nd generation Escorts all used as daily drivers. The OEM exhaust manifold on a 93LX is the same as on my 91LX, 92LX, 93LX and both of my 94LX's. I would not tighten the studs on the exhaust beyond the specified amount. Its important to allow the manifold & head to expand separately. I dont 'think' I have a leak but confess I have never tried to pressurize the exh system with the shop-vac reversed. With my hearing loss, I likely wouldnt hear it anyway. I have also lost my sense of smell. But my wife still has both those senses, and doesnt complain about leaks or odors. When first working on my Escorts, I have found that last-left-most stud behind the alternator to be missing or not have a nut on it. Its the one you cant really reach once the alternator has been installed. Did you take off the exh. manifold nuts, and found that the nut usually brings the stud off with it? Most of mine were that way. I always separate the nut from the stud using my oxy-acteylene torch, and reinstall the studs to the head; putting the nuts on after the manifold is in place. With plenty of antiseize compound on the threads too.
Thanks for the replies; I've tried a couple different gaskets, a fel-pro one that was metallic and the one from dorman that feels like fiber, and they both have leaked the same. When I removed the manifold stud nuts they did unscrew the studs with them. I separated them with pliers. The pliers were fine on the longer studs on the bottom because the plier teeth just bit into the unthreaded part of the stud, but for the upper ones it did mess with the threads at the center so I replaced those with new studs from the hardware store. I think I'll take it apart again and put RTV on the manifold gasket and see if that seals it up.
Permatex ultra copper. That what I have going into my cat and no problems. Sent from my ONEPLUS A6013 using Tapatalk
It really depends on how much bubbles you are getting. The test you are doing will detect extremely small amounts of leakage, so it may not be enough to worry about. Can you post a video?
I was wondering about that too, whether some leakage is normal, but this seems like a lot. The video is a bit shaky but you can see a good amount of bubbles across the top of the manifold: Actually, my phone won't shoot video in a file format that I can upload so here's a couple screenshots of the video:
It's tough to tell from still photos, but if the leak doesn't simply blow the whole soapy water solution away, I don't think it's important. Was that test done after siliconing the joint? I detect leaks by holding my hand close to the source, and I sure couldn't detect the ones posted above.
No this is with no silicone yet, but the bolts are over the torque spec and still leaking. I'm gonna apply the copper RTV and let it cure for a couple days then try the test again.
When you tighten the manifold bolts, are you doing it from the center outwards, similar to how you tighten the cylinder head? If you tighten the ends first, you may end up with a slight bulge in the middle that won't go away with further overtightening. Also, you may want to use all new studs and locking torque nuts which will stretch very slightly when tightened. Dorman has a kit with the right size and number.
Do the manifold studs have non-threaded area. Is it possible the flange on the Dorman manifold is not as thick as the OEM manifold? Maybe nuts are bottoming out before manifold tightens down.
The OEM manifold studs do have a non-threaded area, but its only about the width of one or two turns; like maybe 1.5mm. The stud in your picture has maybe eight or nine missing turns of the thread; so the unthreaded area is actually wider than the diameter of the stud. I would not try to use that stud without adding a few stainless washers to take up the extra length so the nut could seat. When I think of it, I try to put the stud into the head, put the nut on it, and run it down far enough to be visibly closer to the head than the thickness of the manifold where the stud goes through. Same check with the intake manifolds when I have them off. I dont have info about the thickness of a Dorman manifold.
Thanks everybody; I tried looking for a Dorman manifold stud kit for a 93 on their website but I couldn't find anything that said it matched my vehicle- would a kit for gen 3 work on a gen 2 cylinder head? Or maybe a kit for a different vehicle is still compatible? When I was doing the tightening I was going from the center out, and using a torque wrench, except on the far most left bolt near the alternator bracket which didn't have room for the wrench. After using permatex I've driven the car about 20 miles and so far I haven't noticed fumes, no check engine light, and the engine sounds a little quieter so hopefully this all holds up.
It should, just try and get some washers in there and see if that helps Sent from my ONEPLUS A6013 using Tapatalk