Volvo vnl 780 Cummins isx engine ...Help?!!

The upper radiator hose collapsing usually can be fixed by replacing radiator cap. But the cap we have on Volvo isn't vented, so new cap won't help. I might be wrong, but wouldn't worry that much about it.

 

Don't think the squeeze on the hose is anything to worry about, vaccuum caused by water contracting as it cools and the vaccuum to pull water back from the overflow bottle into the cooling system.

as for the other issue with the cruise... Is the jake brake coming on???

 

CK. ele. push button under clutch arm,if clutch spring is not keeping press. on ele. switch cruse will kick off an feel like brakes are on till switch is pressed on agian an cruse comes back on.

 

I've never seen a upper radiator hose on a truck that long, usually it's two hard pipes connected with a short silicone hose. If it is supposed to be that long it should have metal inside of it to keep it from collapsing. It doesn't look normal, might want to replace it.

 

The pressure cap is vented it is the one on the driver side , u should replace it , there also a check valve in the res/ tank that also be causing your problem , been working for a volvo dealership for 15 years and we see a lot of them

 

There is a microswitch on the clutch and brake pedals both are adjustable , if your brake pedal has more 1in of free play you will need a foot valve replaced, its not a good idea to keep adjusting the microswitch on the brake pedal , if its low there is something going on and u should have it looked at, good luck

 

If u check out the clutch pedal there should almost be no free play , if there is check the return spring

 

I've replaced that pressure cap on the side of the tank, and still no change. How do I get to that check valve? Do I need to replace tank?

 

Start with what is the cheapest: make sure your have the proper ratio of antifreeze/water. If you've had the coolant for the few years, change it to be safe. If the hose is oem, change it. Your Coolant tank has two sections, if they are both filled-take the tank off and only fill it to the propped level so that one section will have the antifreeze and the other one is empty. Also, your cap on the driver side, coolant tank, has a hose connected to the tank and that hose runs down - make sure the hose is not clogged. Next, under, meaning on top and under your steering wheel, your clutch pedal is the micro switch. Try zip tying it closed, engaged, and see if that eliminates your cruise issue. If it doesn't, get under your vnl and check the speed sensor and the wiring, sensor is on the rear end of the gearbox by your drive shaft, while there, make sure your shiny, somewhat, pole/abs ring is tight and has no play in it what so ever. If that still doesn't solve your cruise problem, replace your speed sensor, not expensive, if that still doesn't fix your problem, take it in for service.