Prevost 8V71 overheating

[lostagain]

Driving back from Las Vegas, Laughlin. Me in my 5C, runs great, strong, nice. My friend's 85 Prevost XL 8V71 has been using a lot of water when going up hills and fighting strong head winds. Everything is fine as long as it doesn't get hot. But when the coolant temp goes up, it goes way up and shuts down. We find the expansion tank empty and add a couple of gallons or more. There are no visible leaks anywhere. The rad cap is just a cap with no spring or any markings on it for pressure rating. I am suspecting that the hot water goes past the cap and out the overflow tube to the ground. What psi rating should the cap be?

Thanks

JC

[Geoff]

The radiator cap should be 4 lbs.

[luvrbus]

It uses a Stant R3 cap I don't why Prevost is using such a low pressure cap ?, on the highway 8v92 engine the minimum is a 9 lb up to 14 cap without a surge tank

good luck

[wg4t50]

Every 2 stroke Detroit Diesel powered generator seems to come with the 7 psi cap.
I never had any issues with the 10 lb. cap on any 71 or 92 series we ever ran.
Dave My

[lostagain]

Thanks, I'll pass it on.

JC