Upper radiator hose sucking shut and engine temp fluctuating

[ford2018]

I have a 1993 ranger with the 4.0 ohv, me and my dad just did head gaskets on it, put a new thermostat in it, new water pump, new radiator cap, new heater hoses and new upper and lower radiator hoses, it’s not overheating but we’ve noticed that the upper radiator hose sucks shut and then reopens, we hooked a scanner up to it and looked at the temperatures and it would fluctuate between about 210 and 165, we can’t really figure out what the heck is wrong with it, any help would be greatly appreciated thanks

 

[Denisefwd93]

Bad cap, clogged or pinched overflow?

 

[Uncle Gump]

I would bet the bypass is plugged...

Check out this thresd and look at what rond has to say about a plugged bypass. I think it was post 7.

https://www.therangerstation.com/forums/showthread.php?t=178741

 

[ford2018]

we flushed out the heater core and radiator, and it has hot air coming out of the vents so we don't believe that its the bypass, and it shouldn't be a bad cap cause the cap we put on to replace the old one is a much tighter seal and is a murray brand, and the overflow isn't pinched or clogged cause we've seen the coolant being sucked out of the overflow and then going back into the overflow after we shut the truck off, and that shouldn't have anything to do with the upper radiator hose sucking shut considering the hose from the overflow is attached to the radiator, my dad thinks that there still might be some air in the cooling system, and we have something that can put a vacuum on it, so I think we may try that and see if it fixes it or not

 

[Uncle Gump]

Did you actually read the post? Maybe start over on that link from post 1. It's carbon copy of the exact repairs you have done... then the engine temp fluctuates...

Ron D is a pretty smart fella... and even I'm smart enough to know that if you plug the bypass the upper radiator hose will suck closed.

You really might want to try disconnecting the heater core and connecting the hoses together. Run it and see if your engine temps stabilize... and it stops sucking your radiator hose shut.

Either way... happy cooling system vacuuming

 

[Vincenthdfan]

I was thinking about this last night when laying in bed unable to sleep again...ugh, hate anxiety issues

Anyway, you could possibly have been given the wrong water pump at the parts store.

Ford had two different water pumps that look virtually identical to each other.

This could certainly cause your upper hose to suck shut because the impeller would pump in the opposite direction than the belt is turning it.

Also, ensure you have your serpentine belt routed correctly (not trying to insult your intelligence, just trying to make spitball suggestions here). If the belt gets routed incorrectly it will change the rotation of your water pump as well.

 

[Uncle Gump]

A couple of parts listings I just looked at only show one water pump listed for that vehicle. Not saying there isn't two... I'm just not seeing it. Maybe a with or without A/C thing that both parts store don't have in there catalog?

Vince is right... you indeed need to ensure you have the belt routed correctly. Spin the water pump backwards and weird stuff will happen.

I still think the simplest thing you can do in your quest to figure this out is pop off the heater hoses and connect them together... at least it would eliminate beyond a shadow of a doubt that a plugged bypass was NOT the problem.

 

[ford2018]

ok so I may not know what I'm talking about, but I know my dad is cause hes a mechanic and has been one for 30-40 years, and hes a damn good one, and if the bypass was clogged there wouldn't be anything going into the heater core which there is cause its getting heat inside the cab

 

[backporch]

resolution?

Did you ever find the issue with the hose collapse? I have a similar issue on an explorer 4.0 motor that I am in the process of moving to my Ranger.