rust on engine oil dipstick


cruzin1
04-24-2007, 07:59 PM
gmc safari, 1995, 4.3 175,000, helping my son with his gmc, he had just got the van a bit ago, went to change the oil and told me the dipsitck was all rusty. He also had a check engine light on, found out it was 32, the egr valve, I took it out and it was all pluged up with a buttery looking sludge. and also noticed that who ever worked on the egr last had striped some of the threads for the one bolt partially. I think its tight but didnt want to tighten to hard. 3 questions
1.will the bad egr valve casue the rust?
2. how can I fix the threads?
3 I didnt see a gasket behind the egr valve, dont it need a gasket?

any help appreciated.

old_master
04-24-2007, 09:09 PM
#1. Insufficient PCV flow is what causes the rust, not EGR.

#2. Either "chase" the threads with a tap, or install a heli-coil.

#3. The EGR valve needs a gasket, there is one available with a screen that helps break up the carbon before it enters the valve.

cruzin1
04-24-2007, 11:11 PM
thanks old master, i have the boy pick him up a pvc valve. did not see any carbon in the valve just alot of gooyie butterie junk. unless that was needed greese I took out.
thanks alot for getting back so soon.

old_master
04-25-2007, 05:29 PM
There's a little more to it than just replacing the valve....

Introduced in the 1960's, the PCV system, (Positive Crankcase Ventilation) was the first emission control device used on automobile engines. The PCV system is a calibrated vacuum leak that is designed to collect blow-by gasses and condensation from the crankcase and direct them to the intake manifold so that the engine can burn them. Blow-by is the result of a piston rings inability to seal combustion gasses away from the crankcase, and crankcase oil away from the combustion chamber. When the PCV system is operating correctly, it applies a negative pressure, (vacuum) to the crankcase while at the same time keeping it ventilated. The PCV valve itself has a built in safety feature which is a check valve that prevents induction backfire from entering the crankcase.

Here’s how it works: Filtered air is drawn through a tube into one of the rocker arm covers. The air circulates through the rocker arm cover and down through the oil returns and push rod holes in the cylinder head, into the crankcase. The airflow then travels upward through the opposite cylinder head, and rocker arm cover, and into the PCV valve. The hose connected to the PCV valve directs the flow into the intake manifold just below the throttle plate(s). The gasses collected are mixed with the air/fuel mixture and burned, thus reducing emissions. The PCV system operates using manifold vacuum, the more vacuum the engine can create the more efficiently the PCV system performs. As the piston rings and cylinder walls wear, blow-by increases. Along with the wear, the engines ability to create vacuum decreases. As a result, the PCV system operates less efficiently and cannot control the blow-by. When blow-by becomes excessive, the PCV system can no longer maintain a negative pressure in the crankcase. The blow-by pressure, which is positive, overcomes the negative PCV pressure and the crankcase becomes pressurized. The pressurized gasses that the PCV system cannot process will exit the crankcase following the path with the least resistance. That path is out of the fresh air intake tube and into the filter. When the filter becomes restricted, crankcase pressure again builds and will push out a gasket or a seal in order to relieve the pressure, causing oil leaks.

Testing: With the engine idling at operating temperature, remove the intake tube from the rocker arm cover, you should feel a slight vacuum coming from the hole in the rocker arm cover. If you remove the PCV valve from the opposite rocker arm cover, you should feel a strong vacuum at the valve.

Maintenance: The valve and filter should be replaced regularly. The hoses and the passage in the intake manifold should be cleaned regularly with a spray type carburetor cleaner. Changing the engine oil and oil filter regularly will help prevent the oil returns from clogging with sludge. If the returns become restricted, PCV flow will stop, not to mention starving the oil pump of oil!
Hope this helps.

George Wood
03-31-2008, 10:01 PM
To add to the Old Master's advise, if you cannot feel vacuum from the throddle body port it probably is plugged with a lot of blowby residue. On mine the problem went on so long I had to ream the port out. This is diddicult on the Astro but if you get a long shafted 1/4" drill bit and fashion a handle so you can twist it with your fingers into the hose connection part of the vacuum port, you will be able to clean the port enough to get some carb cleaner down there to finish the job. On two of the high mileage vans I've owned I've had to use this proceedure (>200k mi.). When you feel the drill bit hit hard metal, stop! You don't want to damage the port. You may be surprised how much debris comes out. To get the carb cleaner into the port attach a lengh of tubing to the port and spray the cleaner down the tube. Whe the spray no longer backs up the tube, the passage if clean.

ericn1300
04-01-2008, 07:20 PM
thanks old master, i have the boy pick him up a pvc valve. did not see any carbon in the valve just alot of gooyie butterie junk. unless that was needed greese I took out.
thanks alot for getting back so soon.
The "gooyie butterie junk" could be from water in the oil foaming. This and the rusty dip stick could just be from the previous owner not driving the vehicle on long enough drives to get the oil hot enough to purge the normal condensation or not changing the oil frequently enough. Change the oil, filter, PCV valve and clean all PVC hoses, dipstick and oil filler cap and keep an eye on it for future contamination and also keep an eye on the coolant level as a possible source of contamination.

diggin
04-05-2008, 12:21 AM
Rust can also be caused by the engine never getting hot enough either from short driving distances or the thermostat is stuck open not allowing the engine to heat up and get rid of excess moisture.

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