Thread: Cooling system issue

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I recently replaced the engine in my 1998 Z71 parts getter. The issue is when the engine cools down both radiator hoses close down. I took the cap off and the radiator sucked air. The replacement engine was a new crated GM 5.7 four bolt FI vortec 2002 intended for a 3/4 to 1 ton van. It was complete with all sensors, water pump, FI, pan, and torque plate. It was a plug and play installation. A good thing I have not installed an engine in 40 years. It felt good. Does anyone have any ideas?

Are you using a coolant recovery system, otherwise known as a coolant recovery jug or overflow tank? I would replace the radiator cap, sounds like it isn't opening up when things cool down to allow the coolant from the recovery jug to get back into the cooling system(the sucking air sound you heard).

or the hose got pinched during the r&r ..ted

I changed the radiator cap with a new non pressure release. Took it for a ride and parked it. This AM checked the hoses and lower is collapsed. The hoses are new from AZONE but seen to be weak. Option may be to check else where to see if there are better hoses or all are the same. If that does not work then thermostat.

Oop's yes I am using a recovery system.

Lower hose should never ever collapse and should have a metal spring in it to prevent it from sucking shut.. Autozone stuff is cheap for a reason !!!!!

Has to be the cap not letting the vacuum go away. Is the line to the recovery tank restricted? I very much doubt its the thermostat.

Get an accoridan hose, and pull the spring out of it. Put the spring in the lower hose and everything will be fine.

I went be the radiator shop where I purchased the rad. last night. Everything was working OK. He said some systems are stuborn and there was air trapped some where. He said to keep topping the system off to eliminate the air. I topped it off last night and we will see after I take it out today.

If you have a coolant recovery system that has the proper components and rad cap this will not happen--

Thanks Jerry! All the items of the system are new except the recovery system. Just to make sure I will blow it out with a little air, from the rad. side . I think it had an air pocket and me not understanding what was going on should have been topping off the radiator. I did have a series of water leaks that kept me from getting to this issue first. Thanks again.

the overflow tank for the recovery liquid must also be vent to atmoshere