Strange Issue and hissing noise. 1985 gmc sierra K1500 4x4. automatic 700r4.

[jason]

I'm having some problems with stalling when moving the steering wheel.

  When I turn the wheels far right or left (in reverse especially) it dies.
I was in my driveway tonight and noticed that it DIES almost immediately when I reach the stops or ends of travel in a right or left turn of the steering wheel.
As I reach the end of the steering wheel travel (either right or left turn) the hissing gets progressively louder.. and then the engine dies.
(also the tach is indicating that as the hissing gets progressively louder the engine is SLOWWWING down)
My guess is a vacuum leak..... and I'm guessing that the power steering hose creates a larger load on the vehicle when the steering wheel is at the end of its travel?

Does that sound about right or is there another more reasonable solution?

Are these symptoms characteristic of something specific or common?

Thanks for any feedback!

-Jason.

[86silverado]

That sounds like a vacuum leak. Makes more vacuum at idle and when pump puts a slight load on engine causing idle to go lower would make more vacuum which would make it more noticeable. Have you checked all vacuum connections? 

[jason]

I tried checking the vacuum connections with carb cleaner but can't really distinguish between idle changes when listening to an engine and shooting carb cleaner.  My friend is coming over tonight to keep his eye on the tach while I spray carb cleaner in various suspect locations.

Hopefully we find the leak!

Thanks for the quick reply!

[86silverado]

Hope you find it. Probably something simple. How it always goes, also try turning it when your looking under hood and see if you can get a general idea of vicinity it's in

[jason]

So my we sprayed carb cleaner in various locations while turning the wheels to the point of hissing.

It sounds like its in the vicinity of the carb... but I can't be certain.  We sprayed the intake manifold, all hoses, connections, brake booster, vacuum advance, etc, etc. 

Nothing changed the rpms of the vehicles idle.

We're going to take the hood off to gain better access to the back of the intake manifold.. hopefully we overlooked a spot and missed spraying carb cleaner into it.

Any tips on finding a vacuum leak?
Pretty frustrating.  thanks for your help!

[454Man]

Do you have a aluminum intake?

What's under the hood??? If you have to ask maybe we shouldn't race...

[jason]

haha.. I'm new to the wrenching but not a total square.

I have a small block chevy (305) aluminum intake.  It's an edelbrock performer.
Quadrajet carburetor. I deleted the egr and the emissions components.

(the 305 when it actually gets going is just to get me through winter... come next summer its going to be a crate engine-350 with headers).  then we'll race!

[Irish_Alley]

but im can remember my intake giving me fits and forgetting about a little vacuum port under the carb

[454Man]

Please dint pay attention to my sig...
You get left in the dust.lol jjk
There is a vacuum port on the manifold between the carb and the distributor check that they come loose if no sealer is used...
What's under the hood??? If you have to ask maybe we shouldn't race...

[jason]

ok.. I'll double check those connections. 

[jason]

so its definitely a vacuum leak.  both at my intake manifold and the carb base.  dang!

[jason]

I installed the intake manifold incorrectly.  (I suspect its my torquing sequence)... Lesson learned.  I should follow the recommendation of the manufacturer.

Just curious though>

I've seen some videos online where after prepping the surfaces: cleaning, removing old gasket, scraping clean, and using solvent; acetone or lacquer thinner they use different sealing steps.

1 guy said: use rtv sealant on the water jacket ports of the heads and then drop the gasket into place.  Then add rtv sealant again on the mating surface between intake manifold and gasket water jacket ports.

Another guy says follow previously mentioned cleaning procedures THEN add gasket adhesive to head then glue gasket into place.  Then add gasket adhesive/ sealant (gasgacinch brand) on gasket to intake manifold mating surfaces.

Which is best?

Both people recommend sealing ends of block with RTV. 

I've got vacuum leaks in the intake manifold... probably the fact I didn't use the torque sequence procedure.. but just want some feedback from someone who doesn't have any vacuum leaks.

Also... any tips on sealing the carb base gasket?  I just can't understand how less than 15 foot pounds is going to seal as much vacuum as the truck pulls during idle.

Thanks for your feedback,

Jason.

[bd]

...I've seen some videos online where after prepping the surfaces: cleaning, removing old gasket, scraping clean, and using solvent; acetone or lacquer thinner they use different sealing steps. ¹

1 guy said: use rtv sealant on the water jacket ports of the heads and then drop the gasket into place.  Then add rtv sealant again on the mating surface between intake manifold and gasket [around the] water jacket ports. 

Another guy says follow previously mentioned cleaning procedures THEN add gasket adhesive to head then glue gasket into place.  Then add gasket adhesive/ sealant (gasgacinch brand) on gasket to intake manifold mating surfaces.

Which is best?

Both people recommend sealing ends of block with RTV.

I've got vacuum leaks in the intake manifold... probably the fact I didn't use the torque sequence procedure.. but just want some feedback from someone who doesn't have any vacuum leaks. ²

Also... any tips on sealing the carb base gasket?  I just can't understand how less than 15 foot pounds is going to seal as much vacuum as the truck pulls during idle.... ³

Make sure you have the correct intake gaskets!  Don't assume you've been given the correct ones.  Set them in place and make sure they'll seal where they should.  Do not use the end gaskets that come in the gasket set!

¹ Use a rigid 6" - 8" long sanding block (I prefer milled oak) with 80 grit paper attached that is wet with solvent to "surface" the intake and cylinder head sealing surfaces before the final wash with acetone, B12, engine starter fluid, or other convenient solvent that leaves no residue.

² Thoroughly organize your work area and work quickly, so the silicone sealer doesn't set before placing the intake.  If setting an intake is somewhat unfamiliar, do a 'dry run' without sealer to get yourself organized and grooved into a game plan.  Chase all your bolt threads and bolt holes then coat all the bolts with Teflon paste sealant....  When you're ready, make sure that nothing is laying in the valley that doesn't belong (e.g., rags, loose bolts, gasket scraper, etc.).  Squeeze a dab of Permatex "Ultra Copper," or "Ultra Gray," or equivalent into the corners where the front and rear China Walls meet the cylinder heads, then smear Ultra Copper sparingly around the coolant ports on both sides, and both ends, of each intake gasket and set the gaskets in place.  Now, run a 3/16" - 1/4" bead of silicone along the top of each China Wall, overlapping the little tab at the bottom of each intake gasket.  Align the intake over the engine and set it straight down - don't slide it into place.  Thread the bolts in finger tight, then lightly snug them with a ratchet, followed by torquing in three distinct stages, using the proper sequence.  Let it set for about an hour and recheck the torque.  Check the torque again the following day.

³ Use a straight edge and check the base plate for flatness.  Carb gaskets generally don't leak unless the carb base is warped from overtightening, the wrong gasket is used, or the gasket is damaged.  Frankly, 10 lb-ft should be more than adequate to seal the carburetor to the intake.  Are you sure the vacuum leak isn't air sucking around the throttle shafts?

[jason]

Hmm.. excellent suggestions.

I will check the carb for any signs of warping.  The throttle shafts did have some play... but I don't think they'd be making the high pitched squeal I'm hearing because I didn't change anything on my carburetor besides rebuilding it and setting the float.

The vacuum leak wasn't there prior to me making any adjustments... and I just found some VERY loose bolts on my intake manifold.  Maybe it needed just to be re torqued.  I'd rather just redo the entire job properly to see if this eliminates my problems completely. 

After I've done the job properly at least any future problems encountered will (hopefully) not be related to vacuum leaks on my intake manifold.

Now one last question before I get going on this little project..

When you say you are wet sanding the surfaces, what solvent are you using during the wet sanding?

Would acetone be acceptable? Are you trying so smooth out the surfaces to eliminate vacuum or liquid leaks through any in perfections in the surfaces?

How long do you typically sand a surface?  I'm guessing until the surfaces appear to be smooth without any imperfections.. but I'd rather be 100% certain of what I'm doing then kind of certain.. especially with sanding the surfaces of metal... I can't easily rectify any mistakes made after the metal is gone haha.

Thanks for the reply

[bd]

Are you sure you used the correct fuel bowl and bowl-to-base gaskets when you rebuilt the carb?  Are you certain the squeal isn't coming from the throat of the carb - main nozzle/air bleed area?  Why don't you just torque the intake in the proper sequence and listen/spray again?  QJets will tolerate about 1/32" of play in the shaft before problems begin to appear.

You can use acetone, but it dries very quickly, so you have to dip the sanding block constantly.  You can also use Berrymans B12 or even kerosene (but follow up with acetone to remove any residue).  'Sand' fore and aft, more to clean and burnish away any high spots than remove metal.  The process ensures a clean surface for bonding of the sealant.  You would have to sand awhile in one spot to create a low surface with a 6+" hard block.

One last thing....  If you have an EGR valve, check the intake right side gasket rail for flatness using a long straightedge - it's not uncommon for exhaust heat to warp the manifold.