This is topic is it common for 5.0 plenum vacuum ports to clog? in forum Tech Talk at Northern California Ford Owners .
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Posted by bentley mobs a stang (Member # 11119) on
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I have been trying to make the egr in my 90 5.0 functional. I checked for manifold vacuum from the red vacuum line at my egr vacuum regulator, no vacuum. Traced the vacuum line back to the plenum and no breaks on the vacuum line. Pulled the hose off at the back of my plenum (one vacuum port has a line going to my FPR, the other has a line to my EGR), NO VACUUM! I actually hooked up my vacuum pump to the red vacuum line where it connects to my EVR and I was able to apply vacuum going back to the manifold and it held! There is no cap or silicone at the end of the plenum nipple and I was able to stick a paper clip about 3/4 of its length in there. Is there anything under the plenum that could be plugging it? As far as I know it is all metal going under the plenum until it finally goes into it. Is this common? Should I just try to unclog it with a coat hanger? I only get to work on my mustang about 3 hours every monday as I'm trying to prep it for smog and would like to avoid pulling the plenum if possible.
Posted by Duncan Motors (Member # 7045) on
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never seen it happen, pull off that crab vac fitting and clean it out or replace
Posted by Wht86drop (Member # 12104) on
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Plenum takes about 20min to take it out. You might as well pull it and let the ports soak in gasoline or better yet get another intake from someone
Posted by Tom Renzo (Member # 13165) on
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The upper can be removed in 10 minutes wearing boxing gloves. I have seen a couple of blocked uppers but very rare. Good luck!!
Posted by rollininmy50 (Member # 9067) on
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If stock? Have you taken the smog tube out that goes from the cats to the smog tubbing ? Also the tube that connects to each of the heads on the rear of engine, if the tube or holes in the head are blocked with carbon, you will have this issue as well. In the middle of the upper and lower is a hole, we're air goes threw the heads to upper intake, is this clear and free of carbon,
Posted by diablounicorn (Member # 13033) on
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interesting i have no vacuum from the red line either. but i have gt40p heads so the cross tube is hooked on the head, but the smog pump and the tube to the cats is.
Posted by 4IDFOX (Member # 9921) on
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I have seen an intake that had a pool of oil in the plenum . This was on a road race motor that had blow by issues and a pcv that was allowing the oil by.
I could see vacuum ports getting clogged.
[ 2013-12-28, 08:12 AM: Message edited by: 4IDFOX ]
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