GMC 6484966 Breather Assembly, Air Cleaner & Silencer

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Replace the PCV valve every 30,000 miles (48,000 km). The breather filter, located in the air cleaner on equipped models, is replaced when the air cleaner element is replaced. For V6 engines, the PCV valve is located in the right-hand valve cover on 1975-80 models. On 1981-87 models, the PCV valve is located in the rear of the intake manifold. For V8 engines, the PCV valve is located in one of the valve covers depending on the engine. To remove and install, pull the PCV valve and hose straight out of the valve cover or manifold. Use a pair of pliers to slide the hose clamp, if equipped back down the hose and off the valve connector. Twist the valve gently to loosen it from the hose, then remove. Inspect the hose and valve cover grommet, and replace if they are hard, brittle or cracked. Clean the hose with solvent if it is clogged. Install the valve into the hose, making sure it seats fully in the hose. Attach the hose clamp, if equipped around the valve assembly. Install the PCV valve in the grommet, making sure the valve seats fully in the cover grommet.

The PCV valve can be found on the rocker cover because of its running tube to the carburetor. Ensure that you purchase a substitute for the vehicle, engine size, and model year. It has to be removed by pulling the valve with hose still intact through its rubber grommet from rocker arm cover and then remove PCV valve from the hose while noting its position and direction of installation. Before installing it you must compare your new PCV valve with old one to see if they are similar. Push it entirely until seated properly to the end of the hose. If there are imperfections on this grommet, it should be changed with a new one.

To solve this problem, the positive crankcase ventilation (PCV) system circulates fresh air through the crankcase in order to pick up blow-by gases, which are then rerouted back to the engine through a carburetor. Vacuum hoses and a PCV valve, which regulate the flow of gases according to engine speed and manifold vacuum, are the main components of this system. Carbon and gunk that accumulate in the PCV valve and hoses over time may cause them to jam, hence regular scrutiny is needed to ensure they function properly. Poor idling or reduced idle speed may indicate a restricted or stopped flow in the system. To test for proper vacuum pull off the top plate of the air cleaner and remove the hose leading to the small PCV filter. While your engine is idling put your thumb slightly on towards the end of this hose. A feeling as if there is a slight pull or suction tells that air is being drawn through it. If any vacuum is felt there should be further checks since low or no vacuum will mean that blocking has taken place within this system. By shaking it you can check whether the PCV valve clicks; if it does not, it should be replaced because its check needle does not work properly anymore. When running at idle speed with valve removed, engine should result in a relatively strong vacuum pressure. If there's no or very little difference felt in terms of vacuum pressure either way it might indicate blocked vacuum hose or inlet fitting at engine manifold. Clearing out passages clogged at manifold or carburetor require thorough cleaning, while failure of pcv valve necessitates replacement thereof. When buying a new one for your engine just make sure that you don't get something else instead of genuine PCV valves.

The PCV valve is located in the right-hand valve cover on V6 engines for 1975-80 model.

The PCV system should be checked at every oil change and serviced every 30,000 miles (48,000 km).

It's important to ensure that the replacement PCV valve is for your particular vehicle, model year, and engine size.

The PCV valve is connected to a hose that runs to either the carburetor or the intake manifold.

To replace the PCV valve, first, pull the valve (with the hose attached) from the rubber grommet in the rocker arm cover or manifold. Then, loosen the retaining clamp and remove the PCV valve from the end of the hose, taking note of its installed position and direction. Compare the old valve with the new one to ensure that they are the same. Push the new valve into the end of the hose until it is properly seated, and then reinstall the clamp. Inspect the rubber grommet for any damage and replace it with a new one if necessary. Finally, securely push the PCV valve and hose into position.