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  #1  
Old 10-20-2015
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Radiator over pressurizing

I blew a lower radiator hose on my 98 ranger 3.0 V6 2 weeks ago.- I replaced the hose and thought I refilled it completely with fluid.- That evening I overheated my truck taking my son to baseball practice and when I pulled off the road and parked the truck stalled out.- I believe my thermostat was stuck closed and never let fluid into the block so I was extremely low on fluid.- A few days ago I replaced the water pump and thermostat.- Water pump was dripping fluid out of weephole and i thought i fried thermostat by overheating it. I refilled with fluid and at first I could not get the fluid to circulate, it was pulsing out of the open radiator when I was idling.- So I put the cap on radiator and drove it a couple miles hoping that would open thermostat and circulate fluid so I could add more. -I also was not getting any heat inside cab. -When I got home and parked the radiator side was over pressurized.- The top radiator hose was so hard you could barely squeeze it, the radiator was dripping in both bottom corners where the metal meets the plastic, and the top radiator hose was dripping where it meets the radiator.- This only occurred when it was overpressurized not when engine was off or just started.- The reservoir was bubbling and the level of fluid rose.- I was worried that I was getting exhaust into my coolant system and that I blew a head gasket.- I got the block tester from autozone and tested to see if I had emission gases circulating through my radiator or reservoir.- That test came up negative last night.- I also burped some more air out of system and was able to add a lot more fluid.- Truck also started pumping hot heat which is good.- Im thinking the system was air locked at first and I may be on my way to solving the problem.- However the radiator side is still overpressurizing and dripping fluid from both bottom corners of radiator when its overpressurized, not when its immediately started.- Im thinking it may be the radiator cap that's bad and not relieving the pressure?- Also what are your thoughts on bad head gasket or air locked given the symptoms described?
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Old 10-20-2015
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Block test is OK but must be done exactly right or results can be mixed.

There is a simple and free test for cracked head or blown head gasket, the Glove Test.

Remove rad cap
Remove overflow hose and block it's port on rad
Put latex glove over rad cap opening and seal it with rubber band or ??, a balloon or even condom will work in place of glove.
Cooling system is now sealed.

Unplug coil(s) we want a no start.

Crank starter motor and watch glove, if it starts to jump up and down then you have a problem, cracked head or blown gasket.
Cylinder pressure is coming into the cooling system which causes glove to move.

If it just lays there then you are fine, get a new rad cap

If it is bad news, glove is jumping, then remove 1 spark plug at a time and repeat test, when glove stops moving last spark plug removed was from cylinder that has the problem, put plug back in and retest to confirm.


When refilling a cooling system remove one of the heater hoses from firewall or at heat control/bypass valve, this allows air to escape from the engine/heads and coolant to flow in from lower rad hose, since upper is blocked by t-stat.

Last edited by RonD; 10-20-2015 at 03:07 PM.
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Old 10-20-2015
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Ok i will try the glove test tomorrow. I got a new radiator cap today and ran truck up on ramps. Left cap off and turned truck on. Initially fluid was pulsing out of rad opening. Not spraying just surging out. Afrer truck got a little warm it stopped. Im assuming when tstat opened. I topped off fluid and shut off engine while i did something around house. About 30 mins later I put cap on and drove about 5 miles. The temp gage read cold for a good mile and half or so then all of a sudden jumped to normal operating temp. Heat started pumping hot. It was cold before that. I continued to drive it to see if it was going to over pressurize again. Got home after 5 miles and parked while still running. Upper rad hose was normal pressure. I could squeeze both sides until they touched and the hose was hot not warm. So i know tstat is operating. I looked under truck for leaks at both ends of rad and the top rad hose where it meets rad. There were no leaks. I shut truck off and looked again. On driver side it started dripping between plastic and metal of rad. Then after a few seconds it turned to a stream. So i set up a funnel to catch fluid to reuse. I did not think of feeling bottom rad hose to see if it was over pressurized. Dumb ol me. Anyway my rad is shot so i bought a new one at advanced auto for 165 tonight and will install tomorrow. Given that the rad has busted a seal will the glove test still work or do i need to replace that first?
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Old 10-20-2015
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You can test it with small leak in rad.

But doesn't sound like cylinder leak any more.
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Old 10-21-2015
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Whatever was over pressurizing the system busted the seal on my radiator. So im worried once I replace it that it will just happen again.
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Old 10-21-2015
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It is a possibility but there are only 2 things that can pressurize a cooling system.
1. expanding coolant when it is heated, this is normal and causes the 14-16psi pressure the rad cap maintains, but if rad cap fails to open then pressure can increase past this.
Overheating an engine can increase this pressure even more, if temp gets high enough coolant flashes to steam..........and that is ALOT of pressure, they used to run trains on steam power.

2. cylinder pressure leaking into cooling system, do the Glove Test to take that off the table

Both are under your control, replace leaking rad

Loosen heater hose to let air out when refilling.

Last edited by RonD; 10-21-2015 at 03:20 PM.
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Old 10-21-2015
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RonD is exactly right on everything he told you. If autozone is one of those places that rents\loans tools ask for a cooling system pressure tester. Stant makes a good one they are easy to use this way you can test the whole system and not have to replace stuff one piece at a time.
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Old 10-22-2015
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I performed the glove test and only saw very slight movement in part of glove directly over port. Im guessing this was the slight pressure from water pump? The whole glove did not jump or blow up whatsoever. I replaced the radiator a couple hrs after i did the test. Should I do the glove test again? Im pressure testing the coolant system tomorrow and will post the results.
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Old 10-22-2015
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No, you should be fine.
immediately after cranking engine water pump will displace some fluid so you will see some pressure/movement so that is normal.

Leaking cylinder will cause glove to pulse/jump each time that cylinder is on it's compression stroke, unmistakable, and memorable the first time you see it happen.

And yes if you try it on a running engine the glove will inflate like a balloon.
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Old 10-25-2015
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So I replaced the radiator and used one of those special funnels that seal to radiator to refill and burp system. We were doing good adding alot of fluid but after several minutes probably 10-15 once temp gauge started to climb to the C radiator fluid started to pump back up funnel. So I suspect its a slight blown gasket that only leaks by once engine starts to warm up. The guy that was helping me used to manage a ford dealership shop and he said my head gasket is starting to go. That is only thing that would push fluid up the funnel like that. So into the shop it goes Monday for top end rebuild for $1200.
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Old 10-25-2015
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Well.............

Did you loosen the heater hose while refilling?

Those funnel refill devices for the rad cap opening look good but don't really work, because of thermostat location.
And you will get exactly what you describe when engine head gets hot with air in it, a sudden rush of coolant up the funnel when thermostat starts to open, cold coolant from rad enters from lower rad hose, it pushes out the trapped air and contacts the super heated head metal and expands rapidly, instantly adding more pressure to the system which you see as coolant pushing up at the funnel, then burping of the air, and more expanding coolant.
Problem is also that with a head gasket leak it would start pushing coolant up funnel as soon as engine started, you have 1,000+ psi pressure in a firing cylinder, even a small leak will push coolant out of rad the moment the engine starts, no delay for warm up.

Other issue is that a head gasket leak(or cracked head) is more noticeable when engine is COLD, it leaks less when warmed up.
Laws of physics, metal expands when heated, same as coolant does in above example.
Because the head bolts are tight, when the head(and block) metal starts to heat up it expands and presses down harder on the head gasket, often sealing smaller leaks, or at least reducing the leak volume in both directions.

This part is just FYI:
When an engine overheats that is what often kills the head gasket, head metal expands beyond "normal' and crushes metal ring sealing cylinder.
When auto makers first switched to aluminum heads they had a problem with head gasket seals on cast iron blocks, aluminum expands faster than iron, and expands more.
This caused rubbing of the head gaskets as engine warmed up, so they would see head gasket failure in under 30,000miles sometimes, they switched to all metal head gaskets which solved the rubbing issue but heads would leak coolant when used in very cold climates, lol, because head metal did not exert enough pressure when metal was very cold, it shrank too much, so composite MLS gaskets were needed, which worked until all aluminum engines were used.
Just noting this because it shows what happens as an engine is heated and cooled and how it effects head gaskets.

You may have a head gasket breach, but negative results with glove test and what you described above would make me question that.

Loosen heater hose when refilling cooling system, let the air out.
Air is trapped in the head because of thermostat location, opening heater hose allows most of the air to escape as coolant comes in from lower rad hose when filling from rad cap.
Some thermostats have a jiggle valve, a hole in the plate with a metal pin in it, this hole allows air to escape when refilling a drained system, always helpful but loosen heater hose.
It is called a "jiggle valve" because the metal pin jiggles to keep hole open and free from debris.
Jiggle valve needs to be placed at 12:00 position if thermostat is mounted sideways, for best air relief.
I often drill a 1/8" hole in thermostat plates that don't come with jiggle valve.

Last edited by RonD; 10-25-2015 at 02:53 PM.
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Old 10-25-2015
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No i have not removed or loosened heater hose while refilling. At what point would I put the hose back on? Or what do you mean by loosen? Dang now im second guessing trying that out before I let shop work on it. The shop is located about 4 miles from my house. I drove my truck there today and left it so they can start in the morning. My truck idled rough and ran rough at first but then settled out after a mile or two. When i parked at shop and lifted hood, the reservoir had overflowed and was full of fluid. I had one of those rad caps with pressure relief lever on it. I left that up in the open position while I drove to keep system from over pressurizing and busting another rad or messing up something else. When i removed cap the rad fluid was low again. Maybe halfway down or so.
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Old 10-25-2015
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Just let them look at it, if they are honest then you will just have a service bill to pay.

When refilling a drained system you remove a heater hose, then start filling the system via rad cap opening, when coolant starts to come out the hose or it's fitting then reconnect hose and tighten it up.

Now start engine and add coolant as needed to rad, after 5 minutes of idling put cap on, make sure overflow is at least 1/2 full and go for a drive, return after 10 minutes, and let engine sit until cold again, check that rad is full before starting, air is purged at this point.
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