Classic Winnebagos & Vintage RVs

Hello, I had my radiator flushed and I still hear it boiling  after about an hour on the road. Does anyone have a part number or know of a bolt in replacement part number? Other wise I guess I recore.
Thanks Tom
p.s. I want to take a multi-day trip next week

First - are you absolutely sure the correct thermostat (skirted type) is installed?

If so, and there are no other issues, then I would suggest getting a generic aluminum (new) radiator.
Cost will be less, and they are readily available in all kinds of configurations. A good shop can alter one easily
to allow for the extended front tube, mounting brackets, hose locations, etc. 

PLUS - they cool much better! 

Are you sure it is full? If it has an overflow bottle then the radiator should be full right to the top and the bottle should be at least half to three quarters full when hot. This keeps air out of the cooling system. Always fill from the overflow and do not take the radiator cap off once it is filled. Also be sure you have the correct cap in good condition for a closed system.