ready2retire59 Posted February 16, 2021 Share Posted February 16, 2021 Does anyone know the pressure rating (or better yet part #) for the coolant tank cap for a '03 Windsor 370hp Cummins ISL. Somehow mine went missing. I'd like to think it was someone else fault but I was the only one checking things before our last trip! My bad. Thanks for any assistance. Tony Chiulli '03 Windsor, '05 Ram toad Link to comment Share on other sites More sharing options...
Paul J A Posted February 16, 2021 Share Posted February 16, 2021 7# is adequate. Nothing special about that. Had one on a ISL 400, ISX 525 and Aqua Hot 10 years full timing. Link to comment Share on other sites More sharing options...
ready2retire59 Posted February 16, 2021 Author Share Posted February 16, 2021 I just found on iRV2 Forums a replacement cap for the surge tank. https://shop.findmyrvparts.com/searc...h=tank&Submit= I've included the link if anyone is interested. Thank you Tony Chiulli '03 Windsor, '05 Ram toad Paul A , Your response just came through after I posted the link. Thank you Tony Chiulli '03 Windsor, '05 Ram toad Link to comment Share on other sites More sharing options...
PeterSchweizer Posted February 16, 2021 Share Posted February 16, 2021 Pressure varies per engine so call Cummins n they will tell you Link to comment Share on other sites More sharing options...
ready2retire59 Posted February 16, 2021 Author Share Posted February 16, 2021 Thanks Peter. Link to comment Share on other sites More sharing options...
just_john1 Posted February 16, 2021 Share Posted February 16, 2021 Am I missing something? My 97 Dynasty has a screw on cap on the tank. It's a plastic tank with the level sensor in it. John Link to comment Share on other sites More sharing options...
ready2retire59 Posted February 16, 2021 Author Share Posted February 16, 2021 This cap is not a "screw on cap"-it's a 1/4 or 1/2 turn to lock in place-same as an older car radiator cap. It is a pressure cap because the surge tank is pressurized. Tony Link to comment Share on other sites More sharing options...
David White Posted February 17, 2021 Share Posted February 17, 2021 (edited) I note the one you found shows 16# on the cap and since there is no other description I’m assuming that’s what you would get. If that’s correct, it’s too high. You’re asking for trouble with damage to your tank, since many have experienced split tanks due to excess pressure. I’ve found 7# is adequate for my ISL400 (or lower one near that pressure), and the tank will not be over pressured. Edited February 17, 2021 by David White Link to comment Share on other sites More sharing options...
just_john1 Posted February 17, 2021 Share Posted February 17, 2021 Sorry this is what I have. The instructions that come with it are: REMOVING RADIATOR CAP When the engine is cool turn the coolant surge tank cap counrerclockwise slightly untilyou hear PRESSURE ESCAPING, STOP and WAIT until allpressure is relieved before unscrewing cap completely. Add coolant mixture to the level indicated on the surge tank. Link to comment Share on other sites More sharing options...
David White Posted February 17, 2021 Share Posted February 17, 2021 I think this,or similar, is the tank Tony has: Link to comment Share on other sites More sharing options...
just_john1 Posted February 17, 2021 Share Posted February 17, 2021 That looks like a typical expansion reservoir. Mine is much larger and isn't pressurized. I guess old is different (97 Dynasty). Mine also has a sensor that give me a reading on the level of my coolant. John Link to comment Share on other sites More sharing options...
Bob Wightman Posted February 17, 2021 Share Posted February 17, 2021 On my 2004 Monaco Knight the cap is 10 pounds. I just went through all that as I am a new owner to this coach and it was missing, was getting ready to order a new one and then found the original stuck in the frame below the tank. I expect that either the previous owner or the mechanic I took it to for service before bringing it home set it on the tank when adding coolant and it fell down inside, you might want to look around under the tank in case its still there. Bob Link to comment Share on other sites More sharing options...
Hypoxia Posted February 17, 2021 Share Posted February 17, 2021 (edited) This is what Cummins Quick Serve shows for my ISX. The pressure cap is used to increase the boiling point which varies with altitude and percent of coolant. Minimum Recommended Pressure Cap With EGR 103 kPa [15 psi] Without EGR 50 kPa [7 psi] Edited February 18, 2021 by Hypoxia Link to comment Share on other sites More sharing options...
ready2retire59 Posted February 17, 2021 Author Share Posted February 17, 2021 David White: That looks exactly like what I have. What is the pressure reading on your cap? Thanks Tony Hypoxia: I was not aware that diesel engines have EGR. Mine is an ISL. Where would you look to see if it has EGR? Thanks Tony Link to comment Share on other sites More sharing options...
hitechpete Posted February 18, 2021 Share Posted February 18, 2021 20 hours ago, Hypoxia said: This is what Cummins Quick Serve shows for my ISX. The pressure cap is used to reduce the boiling point which varies with altitude and percent of coolant. Minimum Recommended Pressure Cap With EGR 103 kPa [15 psi] Without EGR 50 kPa [7 psi] The cap increases the coolants boiling point. Link to comment Share on other sites More sharing options...
David White Posted February 18, 2021 Share Posted February 18, 2021 18 hours ago, ready2retire59 said: David White: That looks exactly like what I have. What is the pressure reading on your cap? Thanks Tony Hypoxia: I was not aware that diesel engines have EGR. Mine is an ISL. Where would you look to see if it has EGR? Thanks Tony As noted in my earlier post, I lowered mine to 7#. As another poster shows, Cummins says 7# on the non-EGR ISX. I think that’s also true on the ISL which is not a EGR engine in your year engine. I had problems finding a cap that fits the tank opening and lock tabs, because most you’ll find in stores will not correctly lock down to seal. I took mine to a napa store and they matched it up. Of course you don’t have that option, so I’m not sure how to find it. It’s not a Cummins item, but it is something that NAPA would have. Link to comment Share on other sites More sharing options...
Hypoxia Posted February 18, 2021 Share Posted February 18, 2021 3 hours ago, hitechpete said: The cap increases the coolants boiling point. Duh, must have had a dyslexic moment! Thanks for the correction. Link to comment Share on other sites More sharing options...
ready2retire59 Posted February 19, 2021 Author Share Posted February 19, 2021 I went to a local Auto Zone and picked up a 7# pressure radiator cap. Seems to fit and lock down fine. I had ordered the cap from Veurink's RV Center (see link I posted above). When it arrives in a few days, I'll check to see if the 2 caps are mechanically (locking) the same. If they are the same, I'll go with the 7# cap from Auto Zone as suggested. The Auto Zone cap is a 7007 radiator cap AZ sku 799304970071. Link to comment Share on other sites More sharing options...
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