Lower intake manifold gasket

[cmequestionu]

Hey guys and girls,

I'm getting trouble codes p0171 and p0174. I have a Jet power programmer which lets me look at simple diagnosing numbers. The long term fuel trim is holding steady at 25% on both banks. Both O2 sensors seem to be working fine, the MAF sensor seems to be clean. I ran some vacuum tests starting with spraying starter fluid around with no noticable change. I did find a small vacuum line fitting that was cracked and replaced it.

I recently tore down the engine before all this mess to replace the valve seals. The Fel-pro gasket kit I got came with the two piece lower intake manifold gasket. I ran a bead of sealant on the surface area of the block between the two gaskets. A smoke test showed smoke coming out basically in that area in the front.

After taking off the lower intake I noticed that the sealant was still on the block side, the intake side was clean. Like the sealant hadn't adhered to it.

This long-winded explanation leads me to my questions: 1) did I put sealant in the right area? 2) did I use enough sealant? (How much should I use?) 3) is there a sealant you recommend for this application?

Thanks in advance,
Stay safe,
Wash your hands,
Eric

P.S. if pictures will help, let me know.

 

[19Walt93]

Once you get it cleaned up to reassemble, wipe all the surfaces down with brake clean, anything else might leave a film that would prevent the silicone from sticking. I like the Motorcraft gray silicone best.Torque it down following the manual-starting in the center and working outward slowly. You were correct to look deeper when you got PO171 & 174. O2 sensor out of range is a symptom, not a diagnosis.

 

[cmequestionu]

I used acetone last time I cleaned it as per the manual. How much sealant should I use? 1/4" bead, light coat, whole tube?

 

[19Walt93]

1/4" bead or so. We had to pay to dispose of 500 gallons of waste oil we were going to burn for shop heat because the acetone based brake cleaner we were using lowered the flash point to 70 degrees and the preheater oil temp is 120 degrees. I use Castle Shop Solv almost exclusively for brake clean, it's alcohol based. What manual said to use acetone?

 

[cmequestionu]

Per Haynes

 

[19Walt93]

I had access to Ford manuals, never used Haynes. Seeing that I won't use them in the future, either. Lacquer thinner is similar to some carb cleans and they cause problems,too.

 

[JMF661]

Just redid my intake gaskets. Cleaned both surfaces with Emory cloth on a wood block, sprayed and wiped down with brake cleaner. A pretty heavy 1/4” bead of UTV ultra black.
did you clean up the sealing surface, or go too lite on the silicon?

 

[cmequestionu]

I'm thinking I just went a little light with the sealant. It did stick pretty well to the bottom surface that was wiped with acetone. It's all scraped and wiped down with Scotch-brite. I still have some acetone left, and plenty of rags. I'll throw a heavier bead down and see where that gets me. I'll report back after it all comes together. Thanks for the replies.

 

[rumblecloud]

Wellllll......wha happened?
GEtting ready to re-install my lower intake and would like to know how it turned out?

 

[cmequestionu]

Wellllll......wha happened?
GEtting ready to re-install my lower intake and would like to know how it turned out?

Oh, sorry. I had some trouble tracking down some RTV. Finally found half a tube at work. Tried wiping down with acetone and putting like a 3/16" bead. Got it all together, ran a smoke test after a day there was a leak in the back. Took it apart again to find I hadn't used enough. Third time was the trick. Gave it a heavy 1/4" across the whole surface, the smoke test told me it sealed. This was on Sunday. I haven't ran it yet to check for sure. I'll know by Friday when I have time to finish buttoning it up.

 

[rumblecloud]

Cool thanks for the response. Hope it holds for you.

 

[19Walt93]

RTV has a shelf life, you know? If it's too old it won't cure properly. I'm glad the acetone worked for you but I'd get rid of it, gonna burn any brush piles soon?

 

[cmequestionu]

The RTV I got from work is only a couple months old. Acetone is a common metal cleaner for welding (my profession). If it's good enough to clean metal for melting together it's probably good for prepping metal for a surface sealant.

 

[19Walt93]

I hope it works for you. Carb cleaner does a good job cleaning,too, but it will prevent RTV from sticking. I've never had to reseal anything I cleaned with brake clean.

 

[cmequestionu]

So everything's back together, more smoke tests found smoke coming from oil dipstick, it wasn't sitting right because of the headers. Got that fixed, another smoke test, IAC valve was pluming, replaced that, another smoke test, it's coming from two places 1) under the plastic cap on the IAC I just replaced and 2) the pivot point opposite the throttle position sensor. Is there an o-ring or seal that can be replaced?