Long story short: Paid a "backyard mechanic" to put new gaskets on, job got screwed up and and now I have a coolant leak at the front right (passenger) side of the intake manifold (where it meets w/the block and cylinder head). "Mechanic" used the cork gaskets in the kit, which perhaps moved while either dropping the manifold or torquing the bolts. Anyway, now I see that it's pretty common to forgo the cork and just run a fat bead of RTV.
My question: What type of RTV? I have the hi-temp red on hand, but I want to make sure that things are done right this time.
BTW: Never done a intake manifold before. I can clean things, I can turn a wrench, I can read/write english. Based upon this link (hinge), it looks straightforward. But that said, I'm always open to helpful suggestions.
I read a post on a racing forum years ago by an engineer at Permatex and he said the Ultra Grey was the best stuff, I have used it since and had no issues. Turbo headers and flanges we use Ultra Copper it says its good for 700 degrees and I have seen the turbo pipes glow on the dyno and stay sealed.
Drag race engines have a vacuum pump to pull a vac on the crank case and all thats used is silicone, the cork gaskets can get sucked in. make sure all surfaces are clean. Just put some in the corners (block to head) put the intake gaskets on, then run a bead along the block rails (take the tip off the tube) and make sure you get onto the intake gasket, take your time and dont make a mess. Let it set up.
You can coat the intake gaskets with gasket glue or RTV, some gasket glue like Edelbrock gasgacinch seals well but makes it tough to take apart and usually tears the gasket down the middle so you have to scrape the heads and intake. We had a Kaase big block and had to send the intake out, it was almost impossible to remove it and the stuff would not come off, I called them and they use weather strip adhesive on both sides of the gasket and told me to soak rags in lacquer thinner to break it down. It took over 2 hours to have everything clean.
I was told by a permatex rep yrs ago: grey with gasket, red w/o gasket. I asked why then do you sell so many kinds/colors? He answered "cause people want that". Obviously this doesn't apply to the high temp applications but since following his rule of thumb I have no complaints (and no leaks)
Sounds like there are several options that will work.
I have always used the permatex blue for the front and back of intake manifolds. I also put a generous amound around the cooling passages in the head. Its not incommon to see some corrosion and imperfections there. A little sealant cant hurt.
Ha- no stupid questions here- it looks like we are all learning something. I so far got three:
1. Permatex seems to be the brand chosen by mustang enthusiasts
2. No matter the color you will likely be happy.
3. Permatex corp is in the same boat (so far 2 reps and 1 engineer has different opinions on which to use)
I've seen this question come up repeatedly and just wanted to teach a little one post lesson.
Installing an intake manifold is very simple as far as the level of complication involved in general mechanics. However there are some "Do's and Don'ts" that every professional auto tech follows, mostly because they have had to redo a job in the past, maybe several of them.
Here's some tips;
First off DON'T use silicone RTV around the intake port seals. If you want a demonstration of why, squeeze out a blob on something and let it cure for a couple of days and then drop it into a cup of gasoline. After a little while is will swell up and eventually dissolve away to nothing. That's not to mention that it will squeeze out into the intake ports and create a "blockage ring" that will severely compromise flow. THEN it will dissolve as the gas/air mix washes over it when the engine is running, and this stuff all goes right on through the engine. You can use the silicone ring gaskets because the ring is back away from the edge of the port and the gasket itself is what comes in contact with the fuel mix. The ring is a second line of defense and these gaskets work very well. The ONLY sealer product that will not dissolve in gasoline is Permatex Aircraft grade sealer and that is what almost all professionals use.
CLEAN the head surfaces, the end seal surfaces, and the sealing surfaces of the manifold with some type of solvent that dries completely. I use alcohol or brake cleaner. The main point is that there is no oil left on the surfaces - sealer wont seal to oil.
So, with a standard intake gasket wipe silicone on around the water ports on the end of each head SPARINGLY with your finger, and drag a little line out to the end seal area. Then squeeze a large line of silicone (at least a 1/4") across each end seal boss on the block. Don't bother even pulling the cork or rubber end seals out of the package. Those are a throwback to the days before good quality automotive silicone and won't do you a lick of good today.
USE guide studs in the 4 corner bolts - one on the end of each head. You can make these easily by buying long bolts and cutting off the heads and grinding these off smooth and rounded. Screw them in finger tight.
Lay the intake gaskets on the gasket card with the "This side up" down. Brush a fairly healthy layer of Permatex Aircraft sealer around each intake port ring. Then set each seal down over the guide studs on the heads ("This side up" up) and seat the lower corners down even into the silicone on the end seals.
Brush another fairly healthy coat of Permatex Aircraft sealer around the ports on the intake manifold, and then LIGHTLY spread silicone around the water passages on each end of both sides and do a small wipe over to the end seal corners, (Remember to do the front and back on both sides - even though there is no passages on the rear, it still needs to be sealed).
Then just set the manifold down over the guide studs. On many engines the intake bolts need to be sealed, if only so oil won't climb the bolts and leak out under the bolt heads. I use the Pematex as it gives a good torque value and does not harden so you can retorque later without a problem. Use a very small dab on the threads, it doesn't take much.
Drop all the bolts into the unused holes and starting in 2 opposing holes (one on each side) of the middle holes - tighten these center bolts "2 finger tight". (That means holding the ratchet close to the head between your thumb and first finger). Then progressively do the rest like that. Now remove the guide studs and do those four. Now do all the bolts "2 finger tight " again, they will all be loose again at this point.
Almost done. Now torque the intake using the factory pattern and spec, and then do it again and again until no bolts pull up when you draw the torque. Let it sit for about 1 hour and do it again one more time.
OK, now walk away until tomorrow and torque it again. You're done. I've been using this procedure for many years and never have a leak, or sealing problem on the ports.
Sorry for the long post, I hope it helps somebody from having to redo the job. Whisperer."
Personally I really like the Permatex brush-on Aviation sealer for lots of things. I use it on the four corner water ports but see no point in using it on the actual intake ports. The water ports are what give me trouble sometimes (like yours is now). I use Ultra Gray at work so I tend to buy Ultra Black for home use. I always have some Ultra Copper around for high heat duty too. If that's all I have, I'll use any of the three. I find the gray tends to blend in where there is cast aluminum. Black hides pretty well too as it is really just dark gray but the copper stuff glares orange. If it wasn't for the looks I would (and have) just use the copper on everything.
11. If thou be not absolutely sure of thy facts, thou shalt Google before posting thine answer.
I would hazzard to guess that the backyard mechanic didn't use the correct gasket for the year of the heads - using a late model gasket on the earlier heads cause leaks in the corners - exactly where you're experiencing them.... Just make sure that the gasket opening fits right around the coolant passage properly before installing the intake.
FWIW - I've used the cork end gaskets with a little silicone, rubber end gaskets with a little silicone, and straight black and grey silicone - all with no leaks so really I think it's just good prep and being careful during the installation not to push the intake forward/back and roll the gasket off the end (which is were I'm guessing most get their problems/leaks from) With the ford intakes it's easy to make guide studs - just get four 3-4" long bolts and cut the heads off then thread them in the ends of the heads - they'll hold the gaskets and guide the intake straight down and prevents any fore/aft movement.
I'm more inclined to tell folks to use the end gaskets on the engines designed that way as it prevents them from over doing the silicone and getting blobs of silicone inside the engine (and causing problems plugging oil pickups, etc.) I've torn down plenty of engines that looked like they used a full tube of silicone on the ends and another full tube to seal the valvecovers....
Also - if you've got the carb off and can see down the intake ports to the head - make sure the gasket didn't move and isn't mis-aligned with the ports...
1968 Mustang Convertible - Built 306/C4/8", disc brakes.
1966 Mustang Coupe - building for daughter... 5.0 EFI / AOD / 8.8
1990 Mustang NCAA/7-up Convertible
You don't need silicone anywhere except on the intake to block front and rear sealant if you use a good manifold gasket. Get the blue felpro gaskets and you don't need any dealer on them. Of course this only applies to mating surfaces that aren't warped.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.