How To Clean Intake Manifold Gasket Surface

Intake Manifold Gasket Diagnosis

Dorsum in the days when well-nigh engines had bandage iron blocks, heads and manifolds, the intake manifold could be easily sealed with simple and relatively cheap die cut fiber-faced metallic gaskets. Sealer was usually required to ensure a leak-gratuitous installation.

The introduction of multiport fuel injection in the belatedly 80s and 90s meant the intake manifold no longer had to menstruum an air/fuel mixture, only air.

This gave engine designers more liberty to optimize airflow. Manifolds became more complex, and plastic became a popular material for casting manifolds due to its low weight and toll.

Some were also fitted with tuning valves that could reroute the air inside the manifold to change air velocity and flow co-ordinate to engine speed and load.

Trouble Applications

On engines with aluminum cylinder heads, corrosion typically erodes the area around the coolant ports. If the plastic under the sealing dewdrop on the intake manifold gasket is eaten away, the gasket can't hold a seal and will leak. In this case, y'all can't blame the leak on the gasket.

Some manufacturers redesigned the intake manifold service gaskets for some of their problem applications. They've changed the sealing beads from silicone rubber to a tougher material called fluoroelastomer (FKM) rubber, which is much more resistant to oils, solvents and chemical set on.

The location of the sealing beads on some applications has also been revised somewhat. The original OE gaskets equally well as the revised service gaskets are usually black with orange sealing beads.

Installation Precautions

When servicing or disassembling high-mileage engines, pay close attention to the condition of the sealing surfaces around the coolant ports on the heads. If this surface area is eroded or pitted, the intake manifold gaskets may not seal properly when the engine is assembled.

In some cases, it may be possible to make clean upwardly the mating surface on a pitted head by lightly resurfacing the intake port side of the head. Pits can also be filled and sealed with high temperature epoxy fillers, and so sanded or machined flat to restore a shine, flat surface. If the erosion is severe, it might even exist necessary to build up the damaged area by TIG welding the caput or replacing it altogether with a new or relieve casting.

Co-ordinate to one aftermarket gasket manufacturer, the recommended surface finish for the intake manifold and cylinder head mating surfaces should ideally be xxx to 60 microinches Ra (Roughness Average). Another gasket manufacturer said annihilation from twenty to 80 Ra should exist good plenty.

Different the super-shine surface finish that's usually required for late-model MLS caput gaskets (20 Ra or less), the surface finish for almost intake manifold gaskets isn't every bit critical. However, it must exist smooth, flat and clean, with minimal pitting and waviness.

If the intake manifold or intake ports on the head are milled at too high a feed charge per unit, it can leave an undulating wavy cease with ridges and valleys that can be hard to seal. This may event in coolant or vacuum leaks, equally well every bit premature failure of the intake manifold gasket sealing beads.

Overall flatness on both mating surfaces should as well be checked with a straightedge and feeler gauge. Flatness should be 0.003" or less on the mating face of the intake manifold and cylinder head intake ports on V6 engines, and it should exist 0.004" or less on a V8 or straight six.

Equally important, the intake manifold and caput surfaces must be make clean (no grease, oil or coolant picture show) and dry. RTV, other sealants or adhesives should not exist used around the coolant or intake ports on carrier-way gaskets. The only identify RTV silicone may be required is to seal the surface area where the ends of the intake manifold gaskets mate with the end strip seals on the block nether the intake manifold or valley encompass.

It's also essential that the threads for the intake manifold bolts in the head be clean and undamaged, as this tin bear upon clamping torque. New intake manifold bolts are recommended. But if you must reuse the quondam bolts, make certain the threads are clean and undamaged. Also, follow the recommended torque procedure when tightening downward the intake manifold bolts and make sure it is the latest process as the original process and torque specs may accept been revised.

If the intake manifold gasket does not make a tight seal around the coolant ports, information technology may leak coolant into the crankcase. If it fails to seal tightly around the intake ports, it may allow vacuum leaks that upset the air/fuel mixture and crusade idle and drivability issues.

Testing For Air Leaks

Fifty-fifty the smallest leak in an intake manifold tin can crusade a fuel trim problem. Finding a leak can be time consuming using your eyes and ears.

Intake manifold air leaks volition suck in air, not expel it. What is sucked in will influence the fuel mixture and touch on engine and emissions systems.

A smoke machine allows y'all to diagnose multiple leaks in less time compared to other methods. A smoke car tin pressurize the intake manifold and put fume or vapor into the arrangement. If there is a leak, you will see smoke come out.

Connect the smoke auto to a vacuum port similar the supply line to the brake booster. Make sure to cake the throttle torso with the correct sized plug. Also, cake off the PCV system.

Leaking injector seals can cause lean and misfire codes. Conventional testing methods frequently involve flammable gases or putting thick oils on the seals and looking for a change in rpms. But this test tin't exist performed on engines where the intake manifold restricts access. Fume machines can help spot these leaks without any disassembly.

Fume coming from the oil filler or PCV system on an engine that is non misfiring could mean the bottom of the manifold is leaking or has cracked. It tin can also indicate worn valve guides or seals.

Coolant Leaks

Coolant does not magically disappear; it has to get somewhere. External leaks can be seen with the naked middle or past using dyes. Internal leaks can discover their style into the combustion chamber or the oil. Spotting these leaks tin exist difficult.

Ever audit the overall system. Cheque the oil for whatever foaming or signs of contagion. It may be counter intuitive, merely take the fourth dimension to pull the codes. Efficiency or oxygen sensor related codes tin point that coolant is leaking into the combustion chamber. Coolants contain phosphates and other chemicals that tin harm the oxygen sensor and the catalytic converter.

If the engine is a V6 or V8, the codes can even tell y'all which bank is leaking. If the leak is large enough and located in a runner, it might cause a misfire code. If the problem has been occurring for a long period of time, pull the spark plugs. Coolant will leave chalky white deposits on the electrodes. These techniques tin can help to narrow down what is leaking and determine if farther tests should be performed, like pinch or leak-downwardly checks.