In the last post I described replacing the plugged exhaust elbow on my Volvo 2030b diesel. In the process I drained and refilled the cooling system several times. Draining was inefficient and messy, done by removing the hose from the bottom of the water pump. There is a drain plug on the side of the engine, to the right of the oil filter. I made a half hearted effort to get it loose, but it was inaccessible to a regular spanner or pipe wrench. It is a 3/4″ NPT (National Pipe Thread) plug.
After reading on MyHanse.com how another 371 owner had added a tap to the coolant drain, I decided to do the same thing. This would require removing the plug r\that I had previously failed to remove.
The square head is 17mm across. No local supplier had a suitable socket, which needed to be 4 or 8 point, not the standard 6 or 12 point used on Hex heads. I could order one from Europe via the internet but the cost with shipping was ridiculous! A 3/4″ socket extension, reversed, was close enough in size to fit the nut. It was much less expensive so I bought one 4″ long. This extended the nut enough so I could get a regular 12″ Crescent Wrench (adjustable spanner) on the end. I still couldn’t budge it. An 18″ Pipe Wrench (Stillson) also failed to loosen the nut.
I called up a friend who converts vehicles to electric power. He has a large selection of tools. He loaned me a Dewalt Cordless Impact Driver with a 3/4″ square socket (which he had on hand). This made the job so easy, I felt foolish for even trying the alternatives. It literally took about ten seconds. Having the right tools makes all the difference.
The mechanic who had serviced the engine in the past returned my call asking how they got the plug out. He confirmed that they never removed the plug. They used a wet/dry shop vacuum to suck the coolant out of the same hose I had removed to partially drain the system. If I had know that sooner, I might have just done the same.
Although I had drained the engine through the water pump hose, at least another liter, possibly more drained into the bilge when the plug came out. I used MY small we/dry vacuum to suck it up.
Parts needed for coolant drain.
- 3/4″ NPT male to 1/2″ female adapter
- 1/2″ NPT thread hose barb (fits 1/2″ ID hose)
- 3 feet of 1/2″ heater hose
- 1/2″ inline ball valve
- hose clamps fo 1/2″ hose
I installed the above parts, using teflon tape on the joints. I assembled the adapter and the hose barb before installing it, hen used a small wrench on the barb to tighten the assembly in place. There is no need to make it crazy tight!
The hose remains permanently attached to the engine, so that I will remember it is there when next I change the coolant. While everything was open, I brought the dock hose in and filled the system with fresh water. This allowed me to test the drain and also flush the system.
The drain worked great. There was liter or so of brown water then the rest ran clear. I filled the system with coolant and buttoned everything up.
The most valuable lesson for me was how well an impact wrench works for loosening frozen bolts!