Mattmartha Report post Posted March 8, 2016 Just purchased a 2014 Tiffin 33aa with a 8k (HDKAK model - series M) Onan diesel generator. It has 57 hours on it and since its 2 yrs old and I am not clear as to past maintenance, I want to flush and change the radiator fluid as well as replace the radiator cap. I am clear on the procedural steps on flushing and replacing the 50/50 anti freeze. What I need your help on is how full should I fill the overfill recovery tank? It's has a min (cold) mark and a max (hot) mark but surely I need to fill it somewhere in between, right? Lastly, at Napa Autoparts, I can find a 13 psi rated cap but not the recommended 14psi cap. They have a 15psi cap but I don't think that's the way to go. I appreciate any help. Thank you Share this post Link to post Share on other sites
hermanmullins Report post Posted March 8, 2016 Matt, Welcome to the Forum. Go to or call your local Cummins shop and ask the parts department for a 14 psi cap. You could also take your cap to Napa, Auto Zone or O'Rileys and have it pressure tested. It may be just fine. Herman Share this post Link to post Share on other sites
wildebill308 Report post Posted March 8, 2016 This should give you some answers. https://www.youtube.com/watch?v=0LB5ZhvhXas and this one on changing your oil and routine maintenance. https://www.youtube.com/watch?v=CxqkHAAH818 and filter https://www.youtube.com/watch?v=4G8TjuZfyHE I recommend when you buy coolant to use a "low silicate" formula. Bill Share this post Link to post Share on other sites
manholt Report post Posted March 8, 2016 You will also find the recommended Oil and Coolant at any Cummins shop or call them and find the appropriate brand at Wall Mart or Truck Stop! Carl Share this post Link to post Share on other sites
Mattmartha Report post Posted March 8, 2016 Thank you all for your help. Much appreciated!! Share this post Link to post Share on other sites
five Report post Posted March 8, 2016 I use the same brand oil in the gen I use in the big engine...they are both diesels...same oil...Rotella 15w40. The "min/cool" mark is where you should fill the new coolant. The make/type of coolant can be confusing...standard or extended life, I'd call Onan on that one. Share this post Link to post Share on other sites
manholt Report post Posted March 8, 2016 FIVE. Agree, but Onan is owned by Cummins! One stop shop. Carl Share this post Link to post Share on other sites
jleamont Report post Posted March 9, 2016 I called Cummins, got all of the part numbers and pricing, Googled those numbers , bought everything new on EBay (much cheaper for Cummins parts). My oil I use the same as the chassis, Mobil Delvac Elite 15w40 synthetic blend, per Cummins I was told to use the same coolant that is in the chassis, Fleetgard ES Compleat. I agree with the responses above, call them they are great to work with. I used a vacuum cooling system filling tool to fill the generator engine so I didn't have to exercise it to get all of the air out. https://store.snapon.com/Cooling-System-Vacuum-Fillers-Kit-Cooling-System-Filler-P649161.aspx Share this post Link to post Share on other sites
manholt Report post Posted March 9, 2016 Joe. I would need an airplane hangar to hold all the tools you have or have access to! Geez! Carl Share this post Link to post Share on other sites
jleamont Report post Posted March 9, 2016 Carl, yup.... I had my service truck full of tools, My dealership box full of tools and my home box full of tools. I sold the Service truck and most of the home box tools(including the box) when I sold the business last year. The only down side is between the project car in the garage and the tools and machinery from the service business my garage is bursting at the seems . It is nice when you need a specific tool I just walk out and grab it, something metal breaks just go and weld it or make it. What really nice is when I need to change the oil on the coach, I have oil plumbed on a hose reel to a 55 gallon drum with an air pump, I just walk it over to the coach and set the handle to 26 quarts, lock it and walk away. I kept some stuff from the mobile PM trailer I had built. Share this post Link to post Share on other sites
obedb Report post Posted March 9, 2016 Thought your garage looked well stocked last Saturday. Share this post Link to post Share on other sites
jleamont Report post Posted March 9, 2016 Thought your garage looked well stocked last Saturday. Thanks, more like "work in progress" Share this post Link to post Share on other sites
manholt Report post Posted March 10, 2016 Your a tool rat ! Share this post Link to post Share on other sites
jleamont Report post Posted March 10, 2016 Your a tool rat ! Share this post Link to post Share on other sites
