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Jim Grant Tech Tips Jim Grant Tech Tips
A collection of helpful articles based on reader submissions
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Below is a collection of Jim Grant's Tech Tips sorted by Vehicle Make. These Tech Tips were answers to questions submitted to Jim by users over the course of many years.
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Lincoln - Mercury
  Jim Grant's Tech Tips

'90 Jeep Cherokee, Oil Loss Through Valve Cover

Q: I've been losing oil (not burning) in my ‘90 Jeep Cherokee with a 4.0 liter engine. The very top of the valve cover always has a lot of oil on it from the rubber grommet type hose connection to the end of the cover. I ran the engine while looking at the cover and noticed some oil bubbling around this rubber grommet/plug. I'm assuming that this is where the PCV valve is located. This rubber connection leads back through a system of small diameter plastic pipes to the air cleaner. I do see oil or evidence of oil around this system. I'm suspecting that the oil is being blown up and out of this rubber plug type connection in the top of the valve cover and then it just runs down the top of the valve cover and eventually down to the ground. It is my understanding that there is a known historical problem with this engine regarding the valve cover gaskets. But I don't see that the oil is going out of the gasket, as it looks like it's blowing past this rubber plug/connection. Does this sound familiar or common? What is the solution? Obviously I could replace this ventilation system (and PCV valve if that's what it is) but I don't really want to spend the money for plug and chug mechanics. Nor do I want to be ripped off by the Chrysler dealer. Can you give me some answers, suggestions or referrals?

A: Plug and chug mechanics? I like that one. You’re problem is a common problem and it is easily fixed. Your Jeep doesn’t use a PCV valve persay. There are 2 hoses from the valve cover of your engine. The larger of the 2 travels to the air cleaner box. The smaller hose/tube which is mainly plastic travels to a fitting on the intake manifold. The most common problem with this system is the small plastic tube and/or the fitting on the intake manifold becoming restricted and plugged with deposits. The fix? replace the plastic tube and be sure to clean the fitting on the intake manifold. Don’t waste time trying to clean the plastic tube it just doesn’t happen. With a little plugging and chugging your Jeep won’t be blowing oil bubbles any more.

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