1986 chevy c10 305. Water sprays out of radiator cap.

The hose collapses because there is air in the cooling system. If the system is properly full, the hose cannot collapse because water does not compress. If there is a leak in the system, you need to repair it, refill and bleed the cooling system, and ensure that the reservoir has a proper level of coolant in it. If there are no leaks in the system, then the reservoir (recovery) bottle could be low on coolant, allowing air into the system during the expansion and contraction that occurs as the coolant heats and cools. Another thing that can cause this issue is a defective/worn out radiator cap. I would recommend replacement of the cap, refill and bleed the cooling system, then top off the reservoir and then monitor for any further issues.

Hi ,here's a guide on how to do,I have a 85 Nissan 720 4x4,just replaced my water pump,The guide isn't just right,to get to the bolts holding the fan on,we'll the radiator needs to come out,just 4 bolts,maybe 10 minutes.The pump is kind of hard,cause of the way the bolts are.I also replaced my 3 belts,thermostat and both coolant sensors at thermostat housing and radiator cap,the temperature sender broke apart,gauge wouldn't work,lasted 28 years.Had mine 20 years.Check out mine.Here's a site for 720 owners,join,it's free,I'm a member.

Make sure you have the right mix of water and coolant. IT should be 50/50,
check the radiator for mineral build up.
Change the radiator cap.
Change the thermostat.
Check the water pump fins for excess wear

You've already eliminated #3 and #6, so keep checking...

Priority Action Part Type Cause
1 Inspect Radiator Cooling System Clogged.
2 Inspect Radiator Radiator Fins Obstructed.
3 Inspect Radiator Cap Worn or Damaged Radiator Cap.
4 Inspect Radiator Fan Motor Faulty Fan Motor.
5 Inspect Belt Incorrectly Routed, Adjusted (Tensioned), Missing or Worn Drive Belt(s).
6 Inspect Thermostat Faulty Thermostat.
7 Inspect Water Pump Worn, Cracked or Leaking Water Pump.
8 Inspect Radiator Fan Relay Intermittent Failure

sounds like you may have a blown head gasket or cracked cylinder head.

Probably thermostat sticking or bad water pump. CK the belt to the water pump to see if it's loose. If the thermostat sticks, water can't be pumped thru the motor, overheats and overheats the radiator causing hot water or steam to build up pressure.and the relief valve will open allowing the peessure to be relieved and blows coolent everywhere. If the radiator overheats turn off motor wait until the radiator cools before removing cap. been there, done that-------once

if its an Auto u put the fluid down the Dip stick pipe for the Automatic Transmission and the water goes in the water resivour next to the Radiator it will equalise with the radiator water

You probably have water under the distributor cap. Take off distributor cap and spray with Either and wipe out good. Let it set for awhile then put back on and try. If you have air compressor you can blow out cap after you spray with either.

replace carbutator and get it profesional tunned

It has to be one of four things:

1. burst hose on radiator
2. hole in radiator
3. bad water pump
4. blown head gasket
You should be able to visually identify these by looking under the hood while the engine is running. If it is a water pump you should have heard a screeching sound prior to symptoms. If blown head gasket there will be water in your oil. Drain a little oil and see if it is creamy colored rather than black. If no antifreeze, you may see water floating on the oil.

PS- I thought of something else, it could be your radiator cap. When they go bad they let water escape.If it is spraying from behind your engine, it could be a heater hose burst. Oh yeah, if it is overheating before spraying it could be your thermostat.

Good luck,
bob