INTAKE MANIFOLD

ON THIS PAGE:

Installing An Intake Manifold

Plastic Manifold & Hydrolock

 Air leak Symptoms

Rough Idle

3.8 Liter Blows Up


[http://home.teleport.com/~cosa/vap/tech/inmanifold.htm]

How to install an intake manifold


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. I hope this helps save you a lot of hassles.
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Description of Air Leak Symptoms


[General, (2-stroke engines)]... spray soapy water over mating surfaces to see where soap bubbles appear.

use a squirt bottle like a Windex bottle and gently spray water around the maniflod etc. you should see some bubbles or some sort of reaction
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[From a Motorcycle article http://www.nightrider.com/biketech/download/Mikuni_manuals/tune_mikuni_carbs.pdf }

It is easy to test for intake manifold air leaks: With theengine warm and idling, spray WD-40 around thejunctions of the manifold, carb and heads. If the enginechanges from its steady idle, if it surges, misses, etcthen there is an air leak that must be corrected if theengine is to run its best.
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[Toyota http://www.babcox.com/editorial/ic/ic110028.htm ]

Finding an air leak can be a time-consuming exercise in patience. One method is to use a propane bottle and hose to check out suspicious areas. When propane vapor is siphoned in through a leak, the idle will smooth out and the rpm will change. Another trick is to turn off the engine and lightly pressurize (no more than 5 psi) the intake manifold with shop air. Then use a hand bottle to spray soapy water at possible leak points. Bubbles would indicate a leak. Another technique is to use a device that fills the intake manifold with smoke to reveal leaks.
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[http://www.924.org/techsection/1engine.htm (Porsche)]

For the fuel injection, If you have a rough idle, check the o-ring seals for being hard and leaking air past. Squirt a little water around each injector and see if the engine runs rough. If it does, then it's sucking air. The injector sits in a phenolic housing that is both an insulator and mount. These are threaded and can leak around the threads. Any air leak will cause a rough idle.
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[http://www.porschepark.org/garage/ta00022.html ]

"Rough Idle - Intake Manifold Air Leak."

By Steve Grosekemper, San Diego Region

Beginning in 1984, 911's received a new style of fuel injection. This system being Bosch Motronic fuel injection. With this system came many new improvements. Better fuel economy, and idle control being two of the more popular improvements. But as time and miles pass by, a deterioration in idle quality can become a factor. In some cases this problem can progress from a rough idle, to an prominent low speed misfire. The problem occurs when the plastic insulator gasket between the intake manifold and the cylinder intake port collapses, causing an intake air leak. In the first stages the gasket lets small amounts of air to leak into the offending cylinder(s) causing a lean, rough idle. As this problem continues the intake manifold becomes loose enough so that the engine vacuum actually pulls the gasket in producing a large air leak.

The result is a severe misfire at low speed. The repair consists of removing the intake manifolds and replacing the gaskets. This will also remove a substantial volume of cash from your wallet. This problem is one that can be easily avoided in most cases. The remedy is quite simple. When servicing the car at its 15,000 or 30,000 mile maintenance, tighten the intake manifold nuts to 160 in.lbs. The air filter housing must be removed to gain access to the right side intake manifold. The left side manifold will require use of a few special tools to gain access to the 8mm allen nut. I have found that a snap-on, long reach allen with a ball tip works well, tool #FABLM8. Use this in conjunction with a 3 inch extension and an inch pound torque wrench, and you will be able to gain access to all fasteners. If the gaskets don't have the chance to become loose they most likely will not ever fail. (Preventative Maintenance) If this procedure is carried out at each service, the likelihood of gasket failure is all but eliminated. Since we added this procedure to all 3.2l carrera services our customers failure rate has decreased from approximately 5 a year to 1 every other year. Money that could be better spent on a new set of sticky tires! GOOD LUCK
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[http://www.cartrackers.com/Forums/live/YourLemon/395.html.]

GM 3.8 LITER ENGINE BLOWS UP


Posted by blown6 :
I hope someone out there can help me out. Last Jan. my '97 Bonneville SE (3800 V-6, ~68k) literally exploded with fire during start-up. The intake shattered and fire engulfed the engine compartment. I have done extensive research on the net and have discovered that this is a real problem and that GM has been under investigation by NHTSA for nearly 600 similar cases since at least Oct '02. It is suspected that a backfire through the intake is to blame.

In '96 nearly 300,000 recalls were issued for this same thing. However, GM has stated to me multiple times that it is "not a manufacturing defect" even though they openly tell me they don't know exactly what caused it.

I have been battling GM legally since the incident. It is truly David vs. Goliath. I have gone through GM directly, NHTSA, State Farm Insurance, and the Kansas Attorney General. My final option is the BBB. I have accomplished nothing.

We now have a baby on the way and I refuse to put a child seat in this car. However, for ethical and legal reasons I can't sell it at this time either.

Has anyone suffered this same problem? If so, maybe we can help each other out. Is there a forum better suited for this? What about a class action suit against GM?

GM will never see another dime of my hard earned money the rest of my days. Mark my words.

Any assistance would be helpful. Thanks.

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Posted by 01-Jun-03 at 00:17 AM (ET):

I'm a bit confused by your story. Not that the intake on 3.8 engines could self destruct but with the dare I say exaggeration you went through. The 3.8 and the electronic controls should make what you explain impossible. First off the phenomenon of intakes lifting could only happen at key up with the engine stopped at exactly the right position and have one of the coils spark and cause intake damage. But by 97 the software was modified to not allow any spark until the engine produced at least one counted revolution. There was a concern with EGR eroding the manifold but all that produced was poor performance. I also don't understand how you claim the car was engulfed but now you worry about carrying your child. Any fire as large as what you describe would have surely caused more damage than an insurance company could justify repairing.
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Posted by DLSno1 :
My 1999 Buick Park Avenue GM 3800 Series II ~33K did the same thing, but fortunately did not catch fire. This happened on 13Jun03. After the car was parked for two days, I tried to start the engine. The very loud explosion occurred in the engine compartment, shooting smoke from under the hood on both sides. I immediately turned off the ignition and opened the hood. The intake manifold was destroyed. It had split longitudinally and thrown large sections of plastic around the engine compartment. The fuel rail was stretched. The open seam at the top of the manifold was 8 to 12 mm wide. The regulator on the passenger end of the manifold was also blown off.

The repair cost $802. They replaced the intake manifold, fuel rail, and regulator. Neither the dealer nor GM will accept responsibility. They have no clue why it happened, or if it will happen again. The dealer mechanics claim they never saw it before. GM pleads ignorance to any connection to the NHTSA 1996 recall or the current NHTSA Engineering Analysis (one level before recall) on 604 complaints and 44 fires.

I have pictures. What to see?

Your reply from "AngryDad" reminds me of an old saying ... "If it happened, it must be possible". I believe it happened to you. I believe you had a fire. I was comparatively lucky.

Without explaining the causes, GM cannot plead innocence.

DLSno1

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Posted by jsanneman - Angrydad,
I have changed my username from "blown6" but I am still the individual with the Bonneville problems. I assure you there is no exaggeration to my engine fire claims. The cars manifold did explode and the manager of my local GM dealership even testified to this in my repair report. I heard parts hit the underside of the hood. I have both digital camera photos both from my camera and State Farms to prove it. In fact, State Farm was astonished that something like this could happen. My manifold was in countless pieces and some literally melted and dripping down the block. There was around $2k in damages and it would have done much more damage had I not has a fire extinguisher close by. I had the fire out within seconds due to quick thinking on my part. I realize you did not view the incident and you are confused but your accusation of "exaggeration" raises my blood pressure immediately. This is the same treatment I have been getting from GM.
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Plastic Manifold, Melting & Hydrolock

Plastic upper intake manifold -- GM 3.8 liter. The EGR port has a metal sleeve -- but there is still enough heat to damage the plastic around it. When it melts the coolant ports, coolant flows into the EGR port and into the engine, causing hydrolock. Compare the new manifold on the left with the old one on the right that is leaking coolant.
[Photo: www.babcox.com/editorial/ar/elements/110112c.gif]; [http://www.babcox.com/editorial/ar/eb110112.htm ]

Buick 3800 VIN "K" Hydrolock:
One of the more notable features found on the 1995 and later Buick 3800 VIN "K" engines is the plastic upper intake manifold. It's cheaper to make, it's quieter than an aluminum manifold and it makes more power ?but there's a problem caused by the EGR port that passes through the intake manifold directly behind the throttle body.

This passage is partially protected by a metal sleeve that sticks up from the lower manifold, but that doesn't keep the heat from the hot exhaust gas from damaging the upper manifold over the long term. When the plastic deteriorates, it exposes the coolant passages used to preheat the throttle body that are located on both sides of the EGR passage. Then, when the engine is shut off, the pressurized coolant runs down through the manifold, past an open intake valve and ends up hydrolocking one of the cylinders.

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Rebuilders?Survival Tip:
Know the symptoms when a customer calls so you can diagnose the problem before, or after, he installs the remanufactured engine. If one of these engines is hydrolocked, remove the throttle body and check the area around the EGR port for deterioration and coolant leaks.
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[http://www.consumeraffairs.com/automan/plastic.html ]

Plastic Parts in GM Engines


How many cars or trucks have you seen now that have these recycled plastic intake manifolds? Quite a few on the road now, right? I used to joke about 3rd party warranty insurance companies offering to cover an intake manifold because it was something that never, ever went bad. It was like a water pump pulley or hood hinges.

Well I have a heart wrenching tale that is not finished yet (waiting for final warranty decision from GM) but it goes something like this. (By the way, General Motors knows all about this because they sell a ton of these replacement manifolds like hotcakes).

Case: 1998 Pontiac Bonneville. 65,000 miles. Clean car. 3.8 liter engine.

Problem:
Plastic manifold cracks around (very poorly designed placement) EGR return tube that is cooled in water jacket as it passes thru intake housing. Over time hot exhaust gases passing thru metal pipe cause pipe to get hot and coolant enters inside of engine when plastic intake housing finally cracks due to the heat.

Engine swallows enough coolant after a hot run, owner comes out the next morning to an engine that will not crank. Customer is handy, put a new battery and new starter motor in to no avail. Traditional diagnosis AT ANOTHER SHOP, pulled spark plugs and decided it was a head gasket after performing a pressure test (this would be a correct diagnosis in my view but I was suspicious).

Customer was adamant about not overheating this engine ever! He calls me up since now he has no car since October but has been making the payments on it anyway. I try to confirm diagnosis and my pressure test has a lot of air hissing from throttle body which prompts me to remove the throttle body and discover this engineering nightmare. This is like a $600 job if you catch it in time but since the car sat, the engine is now rusted and frozen solid.

I am waiting for warranty consideration after personally talking for the customer with GMAC. Of course they are giving me a bunch of bologna about this whole manifold thing but she will need a new engine if the car is to ever run again.

Every one of these engines should be recalled and the manifold should be replaced because there is no reason on a 3-year-old car that customers should be having a blow up like this. I frowned when I first saw these plastic silly putty parts and now I know my instinct was right.
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[ www.complaintcenter.com/Complaints_Auto/page32.htm#I%20have%20a%201995%20Pontiac%20Bonneville%20with%20a%203.8L%20engine%20&%20melted%20plastic%20intake%20manifold: ]

I have a 1995 Pontiac Bonneville with a 3.8L engine & melted plastic intake manifold:

The upper intake manifold is made of plastic. The EGR tube has melted out of the hole and now coolant leaks inside the engine.

This is a very poor design and should be subject to some kind of manufacturer responsibility to correct.

dmib123
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I have recently had to have the cheap plastic intake manifold replaced on my '98 Buick LeSabre Limited at 69,937 miles:

I have become aware of many other Buick owners with the "improved?" 3800 Series 2 engine having the same problem. It seems that the valve that operates at about 1,300 degrees F. feeds exhaust directly into the plastic plenum. Over time the plastic melts, eventually cracking allowing coolant to flood the crankcase and mix with the oil.

GM is aware of the problem, but since they do not deem it a safety issue, will do nothing if it is out of warranty. All they have done is to configure a "better?" plastic on the replacement part.

Bobbie b.forrest
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[http://www.intellidog.com/dieselmann/symptom.htm#air]

Sucking sound on acceleration --99 F-series:

This could be caused by dirt and water being drawn into the air cleaner. There is a revised air cleaner box that can be installed to correct this--P/N F81Z-9600-BA. If the revised air cleaner box is unavailable, the condition can be resolved by modifying the air cleaner snout: Mark the snout where it enters the fender; remove the air cleaner and cut off the end of the snout 5mm/0.2" from the fender side of the mark; reinstall the air cleaner. The end of the snout should stick into the fender slightly. TSB#98-16-11 I have seen this problem show up in very fine dust conditions without rain.
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[Throttle Body features]

[ http://www.v8sho.com/SHO/fuelsysdesc.html]

Throttle Body:
The throttle body has the following features:

controls airflow to the engine through a butterfly-type valve.

throttle position is controlled by a single lever and accelerator cable linkage.

die-cast aluminum, single-piece body

a single bore with an intake air channel around the throttle valve. This channel controls both cold and warm intake air control as regulated by an idle air control valve (IAC valve) which is mounted to the surge tank connector.

a throttle body-mounted throttle position sensor (TP sensor).
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[Engine Surge ] -

[ http://www.gerull.nl/mg/technics/carb/carb_statter.html.]

Answers:
How about fuel starvation? This could be caused by ...

- blocked fuel filter (inspect or replace)

- blockage in fuel pipe (blow down it to clear)

- fuel pump going u/s

had a very similar problem. In my case it was fuel starvation.

I had partial blockages in the jets; the hoses from the float to the jet had deteriorated inside. I had enough to idle and putter around town but couldn't get up a hood head of steam. Replacing the hoses and jets cured my problem.
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["Answers" to different Engine Surge questions on About.com: http://autorepair.about.com/library/faqs/bl117d.htm]

Surging is usually caused by a bad O2 sensor. But it could also be a sign the fuel filter is starting to clog. It is also possible the EGR valve may be working intermittently.

Before doing this you should clean the IAC, throttle body and passages.

A. I guess the first thing I would do is to give the throttle chamber a good cleaning and see if that helps. A lot of idle problems are cured in this manner. Also check for disconnected vacuum lines since this could cause the problem.

I wonder if that "pop" you hear is the EGR snapping closed? The next time it happens, have someone tap on the EGR valve. If it's stuck that will free it up and allow it to close. Then you'll know where the problem is.
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[http://www.2carpros.com/topics/surge.htm]

... As for the bucking and surging, we first suspect the fuel pump. Installing a temporary remote fuel pressure gauge, driving the car and observing the gauge when the problem occurs can verify if our hunch is correct.

Question: 1997 Pontiac Bonneville 3800 mileage: 60k. My 1997 Pontiac Bonneville SE surges between 1700 and 2500 Rpms only when the car is completely warmed up and going between speeds of 30-35 then 55-60 or anytime uphill at those low Rpms. The car seems to loose power then immediately afterwards will surge back to the RPM it should be. The dealer has replaced the fuel filter, plugs, coils, wires, and air filter, serviced the fuel injectors and replaced the torque converter. They said they now want to replace the transmission to see if that fixes the problem. My guess is the engine is next. No error codes are displayed in their diagnostics. So, they are "experimenting" until they find it or I run out of money. I have already spent over $2,000 for these "services". I noticed someone else with a similar question to you with same car and you suggested EGR valve. Any ideas?

Answer: We would first check the fuel pump to make sure the pressure is within range. If this is okay, try replacing the oxygen and coolant sensors. Sometimes, computers do not set error codes unless components totally fail. In other words, these sensors could be out of range for proper operation of your car without setting a code.
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[http://www.ez.org/HangarFlying/000004ff.htm]

Since owning My Long Ez I have had an engine surge of approx 30-50rpm , which occurs when the engine is throttled back a couple of hundred rpm from cruise power(occurs between 2000 - 2350 rpm mainly in a decent). ----------- I had it before. Try replacing your hoses on the fuel vent lines. It cleared my surge up pretty well. Try turning on your fuel boost pump to see if that clears up the problem. It didn't on mine. Also note your fuel pressure and if it fluxes. Jack
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I have an O-235 in my COZY3. I had exactly the problem as explained before. Last month did the annual and founded a small black piece of rubber in the fuel filter juist before the CARBU.It came from one of the Fuel hoses before it. They had just 10 years since installation and I replaced all fuel and oil hoses with brand new ones. Since then, I haven't got the problem anymore...did about 10hrs since. Take replacing the hoses after 10years seriously guys (and girls)... Hope this helps, Bjorn CFI-ATPL A330 flybjorn


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