Water pump issue at idle

Hey guys,
So yesterday I was trying to see how well my factory coolant temp gauge was working. I fired the car up and had it sitting out in the driveway idling for a while. After maybe 8-10 minutes of mostly idling, a few quick revs in that time as well.
I noticed a nice puddle reading out from my front tire, so I open the hood and see it’s coolant, coming from the cap of my makeshift coolant overflow bottle.
Turn the car off and the coolant level in the “overflow” bottle goes down fairly quickly, back up the tube and into the radiator. Open the radiator cap and the fluid is barely lukewarm, cap isn’t even warm to the touch.
Fire the car up, cap off, fluid does not seem to be moving around, after a minute if idling fluid level just rises back up and out the cap(or into the overflow if the cap is put back on)
If you rev the car the fluid get sucked out of the overflow and through the system, but at idle it starts to push into the overflow again.
If held above idle, probably 1700-2k rpm the overflow bottle is emptied (as far down as the hose going into it) and seems to be pumping the fluid without an issue.
The temp gauge, I do not think is working accurately, but the motor didn’t get real hot through the whole time of messing with it.
The water pump went out toward the end of august 2019, it got a new waterpump,190* thermostat, and radiator since I was already in it changing the water pump. Did not notice any issue between end of august and yesterday with the cooling system. But also never had it sitting just idling for an extended period of time.
Should the car be able to idle for a while and not push the coolant out of the overflow?
I have an 89 lx, 302/t5 car. Supposed to be a mild cam, short tube/exhaust 3.73 car.
 
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Ok. I just checked to make sure it's reverse rotation and it is. So that blows my idea.
I thought of that as well, but for it to work fine for a few months in the summer as my daily driver, and all of a sudden have when it hasn’t been driven a lot in the last two months; and the fact that once it leaves idle it sucks back into the radiator and cooling system, and seems to cycle normally has me thinking it wouldn’t be a wrong rotation thing
 

7991LXnSHO

Mustang Master
Sep 1, 2010
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Have you replaced the radiator cap, or at least made sure the rubber seals are clean and in good shape?
you can pressure test it (and the whole system), but a new cap is called for with all your other new parts, (a Stant with a pressure relief lever is my preference). If that does not do it, you need a system pressure test, and hope it is not a gasket.
 

General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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Some of this is normal operation of the cooling system. You should have a 16lb radiator cap (if I remember) and the overflow tank should only fluctuate during warm up and cool down, about 4-5 inches if you have the stock overflow tank.
i would install a manual temp gauge temporarily to get an idea of what your actual temp is at idle and driving around.
Is your overflow tank stock?
how is your system set up? Maybe some pics?
 

7991LXnSHO

Mustang Master
Sep 1, 2010
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Kearney, NE
General, sir!, I think he said the tank was temporary. And you are right on about this sounding largely normal. That’s why I suspect the cap is not working.there is gunk (stop leak etc.) in the way of the brass center piece, it will not build pressure.
A more accurate set of gauges is always a good idea.
I was also thinking he needed to borrow a temp gun to see how hot it runs.
Fox body cars are notorious for having gauges that randomly max out, starting with the temp gauge, usually with an already full tank of gas. A friend’s 78 Fairmont, my 79 5.0 LX, and an 87 Cougar would do this regularly, and my 91 has done it twice. But they never spilled coolant while pretending to overheat. A “Fonzie tap” to the dash by the driver’s right knee would send them back to normal.
 
Have you replaced the radiator cap, or at least made sure the rubber seals are clean and in good shape?
you can pressure test it (and the whole system), but a new cap is called for with all your other new parts, (a Stant with a pressure relief lever is my preference). If that does not do it, you need a system pressure test, and hope it is not a gasket.
I have not replaced the radiator cap, and didn’t really inspect it. But when I had it off the other day it didn’t seem to have any obvious damage that I recall.
I will have to look and actually check it out better tomorrow.

the new cooling parts have been on the car for 5-6 months now I believe, most which the car was my daily driver and never gave me any issues with overflowing the tank.

my overflow tank right now is a smaller glass jack bottle that has sat right about 1/3rd full from the time I refilled the system, up until the other day when it decided to fill and overflow, but then sucked most back into the system with a light rev/holding above idle.

I doubt my temp gauge has been working since I replaced everything. The gauge got a little hot the last time I drove it before replacing everything.
My gauges started with the gas gauge jumping to above full when the tank was super low, then stuck at above full for probably 6-7 months now, temp gauge hasn’t see anything above a 1/4 way up since I replaced everything I believe, never really paid a lot of attention to it honestly. When have looked, it tends to be around the bottom line, if not pointed straight to the floorboard.

what gasket would you be referring to when you say “and hope it’s not a gasket”?
 

nickyb

Active Member
Apr 3, 2009
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I hope the cap solves your issue.on another note or two a fan shroud will be a good idea,also the stock overflow tank and move the air filter out of the hot engine bay.Good luck and keep on rocking baby got to keep on foxin.
 

7991LXnSHO

Mustang Master
Sep 1, 2010
2,218
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Kearney, NE
I have not replaced the radiator cap, and didn’t really inspect it. But when I had it off the other day it didn’t seem to have any obvious damage that I recall.
I will have to look and actually check it out better tomorrow.

the new cooling parts have been on the car for 5-6 months now I believe, most which the car was my daily driver and never gave me any issues with overflowing the tank.

my overflow tank right now is a smaller glass jack bottle that has sat right about 1/3rd full from the time I refilled the system, up until the other day when it decided to fill and overflow, but then sucked most back into the system with a light rev/holding above idle.

I doubt my temp gauge has been working since I replaced everything. The gauge got a little hot the last time I drove it before replacing everything.
My gauges started with the gas gauge jumping to above full when the tank was super low, then stuck at above full for probably 6-7 months now, temp gauge hasn’t see anything above a 1/4 way up since I replaced everything I believe, never really paid a lot of attention to it honestly. When have looked, it tends to be around the bottom line, if not pointed straight to the floorboard.

what gasket would you be referring to when you say “and hope it’s not a gasket”?
A water pump or thermostat gasket would be OK, but a leaky head gasket is a bigger project.
 
So I put the new radiator cap on it, fired it up and had it sitting out front idling for a a little bit while I was moving some stuff around the garage. It was idling fine and didn’t have a puddle under it when I went back out to it. Opened the hood and could see where the coolant had been dripping into my overflow again and watched a few drips come from the tube. Gave it a quick rev and it came down, but didn’t not drop back into the same small-choppy idle it was at before (car has a small cam in it). I waited a couple minutes and it didn’t seem to be pushing into the overflow again, so I opened the radiator cap, and it instantly pushed out of the cap, so I closed it back down quickly.
Let the car sit there and idle for another 5-10 minutes while I finished the stuff I was doing in the garage and checked again, there was no more coolant dripping into my overflow, and no more coolant in the overflow than when I had walked out.
So hopefully it’s fixed. Haven’t really had another chance to take it out and cruise around and see if there is any problems. And the car is now wrapped up and I’m attempting to fix some of the :leghump: ups I made rattle-can painting the blue door and black roof/hatch and sun spots on the car.
 
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