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Missing Coolant Tank Pressure Cap {Radiator Cap)


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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

 

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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

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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 by David White
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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.image.thumb.png.72040fb72a3e5afb625355aca953bd49.png

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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

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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 by Hypoxia
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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.

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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.

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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.

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