Neat & Clean

Maintenance Q & A - September 2002
Maintenance Q & A — September 2002
By Capt. Ken Kreisler

Neat & Clean
How to service an oil cooler, getting rid of bugs in diesel fuel, and doing a voltage-drop test.

 More of this Feature
• Part 1: Oil Cooler
• Part 2: Diesel Fuel Cleaning, Voltage Drop Test

 Related Resources
• Maintenance Q&A Index

I'd like to service the oil cooler on my 1992 model 740 Volvo Penta stern drive engine. There is no problem getting the unit off, but before I tinker with it, I would like to know if there is a recommended method for taking it apart, cleaning it, and putting it back together. J.H., via e-mail
Although this is a relatively straightforward procedure (refer to the exploded illustration above for guidance), I highly recommend getting the engine manual for this model before you begin.

First drain the engine oil and remove the oil filter. Disconnect the inlet and outlet lines from the oil cooler, and discard the sealing rings so that when it comes time to put everything back together, you won't forget to install new ones. Secure the cooler in a vise after you have padded its jaws to prevent damage. Don't overtighten the vise, as you may damage the cooler housing.

Now loosen and remove the through-bolt and discard the O-ring. Remove the front and rear covers, and discard these O-rings as well. Remove the cooler element from the housing, and examine it for deposits. Soaking the element in muriatic acid for about two hours will loosen up any such residue so you can easily remove it. Muriatic acid, available at any swimming pool supply outlet, is caustic, so wear gloves and protective eyewear. (Safe-React (404) 341-5313,, manufactures a product called Formula E that it claims is a safer alternative.)

After soaking it, rinse the element with fresh water. If you notice solid deposits still present, especially on the inside, gently scrape them off with a half-inch-diameter dowel or similar soft tool. If there's excessive buildup, soak the element for an additional hour and rinse it; you can blow it dry with compressed or canned air. Insert the element into the cooler housing, and install the front and rear covers with new O-rings. Install the through-bolt and new O-ring and tighten securely. Reconnect the inlet and outlet oil lines and new sealing rings, fill the crankcase with clean oil, and install a fresh filter. Start your engine, and check for leaks.

Next page > Diesel Fuel Cleaning, and more > Page 1, 2

This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.

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