Okay, it all started when I changed the water pump with this...
Flow Kooler Aluminum Water Pump, 351W (5.8L)...after I replaced the wqater pump, the thermostat would scale off the chart for a few seconds after the engine warmed up. The mechanic could not figure it out, so he just took the thermostat out and it ran well enough without any issues. After about a year of so of this, I started to get the engine too cold check light. After being tired of clearing this, I tried installing a new thermostat again. I got the same problem. What happens is the thermostat does not open and the top radiator hose will buckle and crimp and the coolant temp goes all the way up. After a few second sof this high temp reading, it races back to being normal. the temp remains normal for a few minutes and then it rises back to being way too hot, and after a few minutes of this, it races back to being normal. This process just repeats itself.

Does anyone have any ideas what I can about this? I am ready to just yank the thermostat back out and deal with the check engine light. Thanks.

 

Just wondering if there is a possibility of a reverse flow water pump having been installed. I know it is possible on the 5.0's, but not sure on the 5.8's.

 

AzPete may be on to something. I know the 5.0 water pumps for the serpentine belt run the OPPOSITE direction of the ones for standard V-belts. I have never looked into this possibility on a 5.8 but it might be worth a shot.

 

For the 5.8 1996, the water pump was only CCW. There aren't any other variants. So, it does not appear possible to have installed a reverse water pump.

302, 351, 351W hi flow water pumps

 

If that is the unit that was installed ok. I had gotten the impression that the pump could have been for an older (non-serpentine) engine somehow. The 5.0 in 96 would have only been serpentine as well.

 

Okay, I'll take a stab at it, and a stab is what it will be!

The fact that the upper radiator hose is collapsing while the engine is running means that the hose has a lower pressure inside, it as compared to atmospheric pressure outside it. A very unusual condition for an upper radiator hose!

Because of this, I ruled out the possibility of a V-belt CW-rotation water pump being mistakenly used with a Serpentine pulley, which should have been rotating CCW since the Serp belt's smooth side drives the pulley. IF the Serp pulley would have fit onto a V-belt pulley water pump (and I don't know if the bolt holes would have lined up) and indeed the wrong water pump was now turning the wrong way for a 1996, it would be PUSHING coolant up through the radiator into the upper hose. With a closed thermostat there, that upper hose would NOT be collapsing, quite the opposite. So I ruled out the wrong-pump idea.

The super pump you bought says on their site that it has a pumping rate double a stock pumps, and that the higher flow rate extends up to 3500 RPM or so where it tails off to be about the stock pumps flow.

So at idle let's say, that super pump is putting a much bigger suction on the radiator, and on the upper radiator hose... and on the thermostat. IIRC, a regular thermostat's moving plate that opens, as it opens, it moves towards the engine side, right? Well, the super pump is creating a strong negative pressure there on that cross-sectional area of that plate, trying to keep it closed. And the thermostat's spring is trying to keep it closed. And only the poor wax pellet is trying to open it. So it has a heck of a time trying to open and stay open. If it closes when it should be open, then the temp will shoot up.

Here is a cutaway view of a regular thermostat on Rockauto's website:
http://info.rockauto.com/Gates/Super...at-Cutaway.jpg
The bottom faces the engine

I suspect, and like I said, this is just a stab at it, that the thermostat you used was the typical everyday type of thermostat. I poked around on that pump website, and on the homepage, under INFORMATION, is a link for Robertshaw versus OEM Thermostats. Open that up, and lo and behold, a discussion about "Balanced" thermostats. It seems to work a bit different than the usual thermostat. It makes me think that the pump company knows that this can happen, and they are recommending that thermostat to use with it. But they don't really come right out and say WHY you NEED to use it.

That's my shot at it.

 

That's some serious thought there. I like it!

 

Is there anyway the bypass hose is restricted? As in wrong gasket.

 

I am unfamiliar with the bypass hose. Can you tell me more? Where is it located and what do I check for? Thanks.

 

 

Yes, that is my impression as well. I have used two of the Robert Shaw thermostats and both times I have had similar problems, although, the condition I am experiencing was/is lessened in intensity and shortened in duration than with OEM thermostats. Unless, I can get more information on this, I will probably just pull the dang thermostat and suffer the red check engine light.

 

Try calling or emailing the pump company, and explain your problem. Maybe they have a solution. I would not want to believe that everyone who uses that pump in a Ford small block has to pull their thermostat out to get it to work out.... hopefully that isn't true!!!

In cooler climates, pulling the thermostat out would be a bad idea for engine longevity. It would also fail an emissions test, as the Check Engine light would be on.

One more thought - You DO still have a functioning heater core hooked up, right? Stuart asked about the bypass hose, and I'm asking about the heater. When the thermostat is closed, coolant circulates from water pump through engine and back to the pump via two routes. The first, which should always be there, is the small bypass hose that takes coolant from the intake manifold water area right before the thermostat, and routes some to an inlet tube on the pump. The second circuit is from the heater supply tube on the intake manifold, through the heater core, then back to the pump on it's own separate pump input tube. If somebody wanted to put a water-shutoff valve in their heater circuit, the bypass route would still be there. But with that super-sucker pump of yours, any way to feed that pump some coolant to its input is a plus. So if you have the heater core blocked, or the heater hoses disconnected and plugged, that would make it worse.

 

[QUOTE=Torky2;10765298]

One more thought - You DO still have a functioning heater core hooked up, right? Stuart asked about the bypass hose, and I'm asking about the heater. [QUOTE]

I still do not know about the bypass hose.

 

Yes, I do have a functioning heater core. Gives me heat in the winter. The bypass hose is unblocked.