Hello again! This month has been quite a learning experience for me. I started April by being reminded of why I left the trade of auto and truck repair 27 years ago. I recall being under, over and inside the engine compartment of my daughter’s Jeep Grand Cherokee after it overheated and blew apart the plastic side tank of the radiator. Needless to say, it caused a very upset kid and a job for the local towing company in my area!
So, being in a proactive mindset, I decided to replace all that might cause another issue in the immediate future, so I replaced the radiator, water pump, all the hoses and thermostat. Very pleased with my effort, I started it up, and guess what? It overheated again in my driveway!
After inventing a few new curse words, I went online to find this is a very common problem with that model vehicle—the electric cooling fan relay fails due to high current draw from the fan. So the coolant gets drained again, the electric fan gets replaced, and it turns out the front bumper has to be removed to gain access to replace the relay!
Well, I’m an HVAC guy, and we know how to cut holes! So a hole gets cut after removing the passenger side headlamp, and the relay gets replaced without removing the bumper! The truck now runs great, the overheating mystery is solved, and I haven’t heard from my kid in weeks!
Sound familiar?
(I shouldn’t complain though—she aced her first year of college! I’m so proud of her!)
So with her truck fixed and out of my driveway, I’m off to start my night shift, and my first call of the evening is an oil leak. Actually, it was really ANOTHER oil leak! A few days earlier, a pinhole in a filter can caused quite a mess for this customer and the technician who was there to clean it up. Now I arrive to find the fuel unit shaft seal is actively leaking, requiring me to again clean up the spilled oil under the boiler and clean up the burner.
I had two more similar calls that week involving leaking filters, and since we’re now in the preventative maintenance time of season, I decided to do some homework on what my criteria should be to either reuse a filter can or simply replace the complete assembly. During my time in this trade, I’ve never had to replace a large filter can due to a pinhole leak, but I’ve had to replace many of the smaller cans. After a few phone calls to the filter manufacturers, I thought I’d share what I found:
Click on image for larger view
The first is the filter can thickness: The 1A25 size is .065″; the 2A700 size is .076″ [See Figure 1]. The thicker metal of the larger can appears to make it more resistant to deforming when the bolt is over tightened. [See Figures 2, 3, and 4] In comparison, the spin on filter thickness is .020″.
With my mind still on torque values—after working on the Jeep—I wondered how tight the filter can bolt should be. After all the years doing this, I never knew. My good friend, Glen Bonelli from General Environmental, dropped off a few filter cans at the school while we were setting up for next semester, and for the first time, I was able to compare what happens to the can after the bolt is over-tightened. The bolt is tightened at the factory to 140 inch pounds.
Click on image for larger view
Converting inch pounds to foot pounds gives us 11.66 foot pounds (inch pounds are divided by 12, the number of inches in a foot, to achieve footpounds; so 140 inch pounds divided by 12 = 11.66 foot pounds). Now I’m convinced I’ve overtightened many filters! I feel overtightening the bolt distorts and weakens the filter can, as you can see in the comparison photos.
The biggest cause of overtightening is when the paint under the bolt washer starts to flake off. In an effort to seal the leak underneath the bolt, the technician tends to tighten the bolt even more. To alleviate
Click on image for larger view
this, I now scrape away all the paint under the sealing washer before reassembling the filter. I also take much more care in cleaning out the filter can before inspecting it and qualifying it for reuse. I found using a paste flux brush works great as a filter can cleaning brush. Any sign of rust, pitting, water staining, flaked or chipped enamel, or distortion of the bottom of the can from overtightening will disqualify the can for reuse. These days, you just can’t be too careful! [See Figure 5]
Click on image for larger view
So how tight is approximately 12 foot pounds? After you feel the bolt start to snug, it’s then approximately one full turn, just like a spin-on filter. A spin-on filter is three-quarters to one full turn tight after the gasket makes contact.
In the last few years, there have been some design upgrades to the cartridge filter assemblies. The cans went from steel to galvanized steel to resist corrosion, and now, most are epoxy coated as well. The bottom bolt and nut have seen some strength improvements as well. [See Figures 6 & 7]
Click on image for larger view
I also was curious to the micron rating of the filter elements:
Spin on: 10 micron
Felt: 10 micron *nominal
Cellulose Acetate: 10 micron nominal*
*Nominal means it will filter most of the 10 micron particles
Click on image for larger view
I also now make sure the filter is properly supported, and prevent the can from resting on the concrete basement floor in case the vibration from misaligned burner fan might wear a hole in the bottom.
Click on image for larger view
Well, that’s it for filters, but again, we can’t be too careful—any discoloration around the burner will prompt me to remove the fuel unit to check the shaft seal, a good way to prevent an additional clean up and an upset customer.
When replacing filters and inspecting burner components, a little more proactive time inspecting will save many more reactive headaches later!
Pool Heater clarification
While working on an “OIL HEAT CARES” project this month, I received some feedback on my pool heater article, and a mention was made I left the most important thing out of that article by my fellow OESP member, Tom Olsen. So, here it is, because he is ABSOLUTELY correct: After working on the pool heater, LEAVE IT OFF! That’s the proper procedure unless instructed differently by the customer. If left running, it’s a given that a call to the office will follow, with the customer asking to be reimbursed for the fuel used while it was left on! It’s happened to me!
Stay safe!
Wayne
