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Nuts and Bolts: Leaky Cummins

Posted in How To: Tech Qa on May 25, 2018
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I recently purchased a 1997 Dodge Ram 2500 with a 12-valve Cummins. The plan is to make it into a tow rig for my other toys. The truck runs great, but it leaks a lot of oil when running. There’s this thing near the power steering pump that visibly leaks while running, but it quits when the engine is off. It looks like the power steering pump is driven by whatever it is that’s leaking. I’m new to diesels in general and Cummins engines in particular. Is it a big deal to fix or should I just take it somewhere?

Harvey H.
Via nuts@4wor.com

You can’t do much better than a Cummins-powered Dodge for a tow rig, but while the engines are legendary, they do have their quirks. One of them is the vacuum pump, which is notorious for leaking engine oil. The pump itself is driven by the timing gears on the front of the engine (although the pump itself is untimed), and the power steering pump is driven off the back of the vacuum pump. Wear-and-tear causes the vacuum pump to start leaking, and when they start leaking they tend to leak a lot. Fortunately, the fix is fairly simple and requires no special tools, but it does take some time to get to extract the pump from the engine in order to reseal it. The seal kit itself is less than $20 and is available from Diesel Power Products (dieselpowerproducts.com) as well as several other online retailers.

As far as the procedure goes, at first it looks as though the vacuum pump and power steering pump need to be removed as an assembly. While that’s one way to do it, it’s not the easiest. You have to pull more things apart in order to gain enough room to remove them together, and you have to crack into the power steering system. The better way is to separate the power steering pump from the vacuum pump in the engine bay and simply slide the power steering pump out of the way. The nuts holding the pumps together are awkward to get to, but it is possible to reach them with some patience. Once separated, you can unbolt the vacuum pump from the timing cover and remove it. As mentioned, a genuine Cummins seal kit is less than $20, and rebuilding the pump is a simple benchtop affair. Once bolted back to the timing cover, reattaching the power steering can be a bit tricky due to getting the cross-shaped plates to line up, but rotating the pump a few times by hand should enable you to seat it. If it really fights you, you can apply light pressure to the power steering pump and have someone bump the key to get the cross plates to line up.

Due to the labor involved, shops charge $400-$500 to rebuild the vacuum pump, so you can save a significant amount of money doing it yourself. Once you’ve done it, however, you might think having a shop do it is a pretty good deal.

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