I put a new intake manifold on - no more 3X2 just a four barrel. Any way I took it out for a spin and when I got on it on the highway I started smoking. Got back home and when I rev. the motor (oh SBC 350 by the way) I could see oil spewing by the oil pressure sensor. It is electrical so it has a 1/8 NPT going into the block and a 45 female/female and then the sensor on top wired to the gauge. I took this all out, ran a tap through the threads on the block - got a little metal in the grease the first time through and none the second. Reinstalled with teflon tape on all threads - still leaking. The spot for this is very close to the edge of the intake where I laid a bead of silicone when doing the intake install. I am wondering if the leak is from the intake or the oil pressure. One friend is convinced it is the intake another the pressure outlet. Here's why, the first thinks since I re-did the plumbing properly and just changed the intake it is the intake. The other friend says it would just seep at the intake and not shoot out like it is (as if under pressure) so it must be the oil pressure threaded area on the block??? What do you all think????? My last effort to problem solve this was I bought a brass plug with 1/8 NPT and put the same silicone I used to install the intake on the treads and tightened it up nice and snug. I am letting it sit at least over night and maybe more depending on weather (truck is out side) and will see if I still get a leak and if it does see if i can tell where it is coming from......... Thanks!!!
I've screwed up the bead at the back of the intake several times...it makes an oily mess back there, easy to mistake it for the pressure sensor. One giveaway is that it takes a little while for the intake leak to happen, the pressure fitting will leak immediately
No need to put any sealant on a brass plug in cast iron, if the threads are good it will seal upon installation .
Never use Teflon tape on oil sensor threads. The tape will insulate it and it needs the ground path to the block to read pressure correctly.
Not if you only use a turn or two. Have you ever taken apart a pipe thread fitting that had teflon tape on it? Mostly there's bare metal on the threads. The tape fills in the gaps.
Have this happen to me before. With a new sending unit too. Frustrating. Since you replaced the sending unit with a plug you'll soon enough if that was the problem.
this..get rid of the cheesy rubber gaskets and run a quarter inch bead of the right stuff or something comparable.
Ok checked tonight with the plug & it is definitely the edge of the intake. I know I should re-do the whole thing but could I can I take the coolant below the intake loosen the intake bolts -see if I can raise that end a bit and squirt more silicone/ gasket maker in there tighten up & let it cure for a day .....??? Posted using the Full Custom H.A.M.B. App!
Sure you can try. My luck the intake gasket would fail and dump coolant in the engine and take out the bearings. Feel lucky?
I had a leak like that and did what you're suggesting, just to get me home. Redoing the install, with a good sealant, cured the problem. Fix it properly. You've gone this far, go a little further.
I've redone stuff not knowing what the problem was. But redoing it fixed it. You know what the problem is, take the time to do it right again. You won't regret it. Posted using the Full Custom H.A.M.B. App!
Ok you are all right doing it right is the thing to do! As Salt flats said above - it could be do it right now or pay me big time later...... Guess I know what Im doing this weekend
There is a trick for re-sealing such a leak without disassembly, which will likely work, but it IS a kludge and definitely an inferior approach... If you want to try... Drain all oil. be sure oil filler is sealed, plug and tape wherever the air inlet for venting system is. That would be the hose from a valve cover to rim of aircleaner on a stock chevy... hook up a hose the where the PCV goes and run it to the manifold of a running vehicle. If you did everything right, your crankase and valley will be under vacuum and for diagnostic purposes you should hear some hissing at your leak as air enters. Feed the leak some spray brake cleaner to de-oil the mess, then put on your gasket goo which should now be pulled in and thoroughly plug the mess. Note this is about two thirds of the trouble to just do it right...this kludge is more appropriate when you are forced to fix someone else's car, not your hotrod!
why would you even consider any quick fix? Pull the intake and make it right...go get ANOTHER gasket, clean the mess up and re-set the manifold.
Ok I obviously did not lay down an adequate bead - any other word s of wisdom in terms of prep or otherwise? Any particular sealer/gasket/silicone product better than another?? Posted using the Full Custom H.A.M.B. App!
I've run a shop for lots of years. Permatex Ultra Black is the only RTV silicone that you'll find here.
One thing I do is put some short 3/8 small studs on the heads so I can set the manifold on the money without slipping the bead away. Then put the rest of the bolts in and replace short studs with the bolts. You only need a couple studs. Like everybody says do it right. If you lift the manifold good chance it will fubar the gasket and like he says create a nice flow of antifreeze into motor. Good luck, Gerry
Definitely do it over again. Before you pull it apart again use a small 90degree pick or a pocket knife to remove a section of the sealer and make sure it comes out not goes in. Measure the gap using feeler gauges. Record this measurement. When you reassemble use an engine cranes or a block and tackle to lower the manifold into place and make sure it touches down straight down and only once or you will destroy your bead. Using a crane lets you get all the bolts started first and you can use them to pull it down to seated. Near enough isn't good enough, good is near enough! Mechanics start what they finish.
Forgot to mention to make sure your new sealant bead is at 2-3 mm thicker than your measurement. Also make sure the crankcase venting system is working efficiently as crankcase pressurisation is a common cause of oil leaks. Good luck bud.
Completely removed, all cleaned up. Reinstalled & let sit for 24 hrs - the full cure time according to the tube instructions-first run a little coolant leak. Carb off re-tourque all bolts - back together no leaks!! Posted using the Full Custom H.A.M.B. App!
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