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What is wrong with my cooling system!!!


fr7

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I posted a thread before about this but I'm gonna start over again, hopefully you guys can help me.
Short story long. I blew a radiator a few months ago, replaced it, few weeks later blew again. After over a week and countless beer I changed the thermostat, water pump, radiator again, fan clutch, refilled with fresh antifreeze. I spent 30 minutes bleeding the air, did this twice, I even rented a pressure test kit and tested the system and radiator cap, everything seemed good.
After 2 days it started to blow the reservoir cap again, it won't overheat, it just blows the cap even when the truck is not up to temperature. It's building so much pressure the reservoir gets full with antifreeze and bubbles.
I don't know what to do anymore, no coolant in the oil or vise versa. I'm hoping new thermostat failed but I'm still getting hot air out of the vents. I'm thinking about removing the thermostat and drive it for a few days to see if it does it again, if it does then I have bigger problems.
I've heard about exhaust pressure going into the cooling system, I'm not sure exactly what that means but I kinda get the point. I haven't done a test for that yet but I guess that will be the next thing to try.
Water pump and thermostat are duralast brand from AutoZone, have lifetime warranty, used Prestone antifreeze, mixed it 50/50.
It's a 98 ranger 4wd 3.0 manual, I don't like driving a baby blue Silverado but that's what I have to drive and I'm glad I put a new transmission in it. I want the little ranger to run without blowing anything up, anybody has suggestions??? Thanks a lot guys..
 


Rearanger

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After 2 days it started to blow the reservoir cap again, it won't overheat, it just blows the cap even when the truck is not up to temperature. It's building so much pressure the reservoir gets full with antifreeze and bubbles.
I'd say you have a crack in a cylinder head inside the combustion chamber. Is the truck a little hard to start after sitting and produces a lot of white smoke on start-up?
 

fr7

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No, it starts right up, even after sitting for a week when I was working on it it started with no problems. I don't have any smoke out of the tailpipe at all. It's just weird it took a few days to blow the cap after I got it done.
By the way the last 2 radiators blew right at the same exact spot, right below the upper radiator hose..
 

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Cooling system pressure comes from the coolant heating up and expanding in volume.
Water pump just circulates coolant it adds no pressure

Only other pressure in an engine system is in the cylinders, which have 150+ psi when cranking, compression, and then 1,000+ psi when running/firing

There is a simple and free test you can do to see if cylinder pressure is leaking into the cooling system, the Glove Test.
Cold engine
Remove rad cap and over flow hose
Coolant level should be at least 1" down from the top of the radiator for the test, drain some coolant if needed, if lower no top up is needed
Plug overflow hose outlet, vacuum cap, gum, putty, ??
Put a Latex glove over rad cap opening and seal it with a rubber band
(you can use a balloon or even a condom in place of the glove)

Disconnect coil or coil pack(s), you want a No Start

Crank engine and watch the glove
If it starts to bounce then you have a cylinder leaking pressure into the cooling system, for sure

If it just lays there then you don't

If it does bounce you can then ID which cylinder has the leak by removing 1 spark plug at a time and cranking engine again
When gloves stops bouncing last spark plug removed was from the leaking cylinder, put it back in to confirm
 

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Thanks Ron, I'm gonna try that next. I hope it turns out negative, otherwise I've been thinking about pulling the motor out and fix all the leaks anyway so if it comes to that I'll do a major overhaul.
 

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RonD, you really amaze me sometimes.

To that end, I’m posting a comment you placed on my thread here, in case it’s of any use to fr7. It was very informative for me:

"Overflow tank on this type of system needs to breath.

As coolant warns up in the engine and radiator it expands in volume
This is what creates the pressure in the cooling system
If rad cap rating is 14lbs pressure then at 15lbs it is push open and hot coolant flows out the radiator to overflow tank and comes in at the BOTTOM of the tank, bottom is important.

When engine is shut off and cools down coolant shrinks in volume, so the 14psi pressure goes down, if hot coolant was sent over to overflow tank then pressure in the cooling system will drop below 0psi, and Second smaller valve in rad cap will be pulled open and coolant in overflow tank will be sucked back in to radiator.
This keeps radiator topped up to the very top.

If you pull off rad cap on cold engine and coolant is not at the very very top then there is a problem in this system

The radiator cap is at a high point in the cooling system, as coolant circulates any air will make its way to the top of the radiator and stay there.
So when coolant expands enough to push open rad cap the AIR will be the first thing pushed out into the overflow tank
The hose from rad to overflow tank must come in at the bottom of the tank so any air will bubble up to the top of the tank.
Then as engine/coolant cools down coolant will be sucked back in from bottom of tank not air, this makes the system self purging of any air in radiator, and why tank needs to be vented, to release the air.

If you have cooling system leaks then places where coolant comes out can also SUCK AIR IN as engine cools down.
It is much easier to pull air in from the outside than to suck coolant back from the overflow tank, coolant is heavy, air is light no contest, lol, air will be sucked in at 0psi.

If this is the case then there will be air in the cooling system every time you start the engine, and when coolant heats up and rad cap opens overflow tank would be bubbling like crazy as it purged the air first.
So top of overflow tank would get splashed with coolant every time.
If you fix engine/radiator coolant leaks the splashing will stop

In normal operation coolant flows out to overflow tank and then is pulled back in, no splashing in the tank, so dry cap.

Purging or bubbling of air in the overflow tank would only happen after engine was fully warmed up, so takes a good 10 minutes +
If you see bubbling within a minute or two after cold start then you have a blown head gasket, or cracked head

Sometimes vehicles will bubble after shut down, this means there is air in the engine, obviously, and that there are pockets of air in the heads, when you shut off the engine you also shut off the water pump, the heads are still hot, if there is air in the heads then it will flash to steam against hot head metal, this bumps up pressure in the system above the 14psi and pushes out the other air at the top of the radiator."
 

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Thanks guys for the good info.
So yesterday I replaced the 190° thermostat with a 160° in the effort to keep the pressure down.
Now the temperature won't go up to normal, it stays between the 2 cold marks way at the bottom, even after driving it for a while.
My question is, would running the engine that cold cause any damage? Will it stay on closed loop, affect gas mileage, mess up the O2 sensors, etc? I'm getting hot air out of the vents and seems to run normal, no check engine light. Should I put the 190° thermostat back? I just want to make sure I don't damage anything else. Thanks for the help.
 

ForTheLoveOfMonkeys

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You are what you do when it counts
So yesterday I replaced the 190° thermostat with a 160° in the effort to keep the pressure down.
Wow that's a big drop

My question is, would running the engine that cold cause any damage?
Complex question... short answer is yes. Cold engine = cold oil. Cold oil = more moisture content and less corrosion resistance. Also affects your mileage so will inherently affect your wear on the engine. Not exactly a short term problem but long term it will take its toll on your engine components.


Will it stay on closed loop, affect gas mileage, mess up the O2 sensors, etc? I'm getting hot air out of the vents and seems to run normal, no check engine light. Should I put the 190° thermostat back? I just want to make sure I don't damage anything else. Thanks for the help.
Closed loop -Yes
Gas Mileage - Yes. Especially with a 30 degree difference. You'll see much lower performance too.
O2 sensors - Dunno about how this would affect them or if it would at all
190 T-stat - I'd definitely recommend higher than your current 165 unless you live somewhere like Hawaii or Kuwait. At the very least you're shorting yourself on fuel and performance. My temp gauge needle doesn't even start to move until it hits 165 and with a 165 t-stat your engine likely isn't even hitting temperatures of 185 which is just below midpoint on my truck.


EDIT:

Looking back at your post... you've blown two radiators in the exact same spot on this truck right?
Something tells me that this is not the radiators' fault. Definitely run the glove test or a block test to make sure you're not getting any exhaust gasses in there and I'd highly suggest a pressure test of the cooling system. Sounds like pressure is being applied to the system pretty consistently. You need to find out where it's coming from before you're onto radiator #4.

Quick test is to go out to the truck a few hours after it's been driven hard (at right temperature) and feel the upper radiator hose, if it's still firm then your problem is coming from the heads or block. If not then you may have gotten away with an air leak somewhere else like a loose fitting or a dying water pump.
 
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fr7

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I did a pressure test, it held up for a good 10 minutes so I'm positive i don't have any leaks.
I'm gonna put the right thermostat back and do the glove/condom test tomorrow. I did notice a little bit of gas mileage decrease today though.
I have to make time to work on this thing, that's the hard part, by the time I get home it's late and I'm tired but I'll push myself to do it. I'll park it in the garage tonight and drive the baby blue Chevy tomorrow. Every time I stop I pop the hood and check everything, the upper hose is pressurized but it gets softer after it cools down, the lower one is always a little more squeezable, and the overflow reservoir bubbles slowly letting pressure out, then it sucks coolant back into the radiator.
I think I might still have air in the system, when I start the truck I hear something gurgling.
I really appreciate your help, I'll post back with the results.
 

Denisefwd93

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I did a pressure test, it held up for a good 10 minutes so I'm positive i don't have any leaks.
I'm gonna put the right thermostat back and do the glove/condom test tomorrow. I did notice a little bit of gas mileage decrease today though.
I have to make time to work on this thing, that's the hard part, by the time I get home it's late and I'm tired but I'll push myself to do it. I'll park it in the garage tonight and drive the baby blue Chevy tomorrow. Every time I stop I pop the hood and check everything, the upper hose is pressurized but it gets softer after it cools down, the lower one is always a little more squeezable, and the overflow reservoir bubbles slowly letting pressure out, then it sucks coolant back into the radiator.
I think I might still have air in the system, when I start the truck I hear something gurgling.
I really appreciate your help, I'll post back with the results.
Let me just toss this in here, in all of the thread here I see no mention burping the heater core? I'm a strong believer in 185 thermostats.

10 minutes is not IMO, a pressure test.
 

fr7

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So how long should I have the system pressurized? I would think 10 minutes at over 16 psi should be plenty to find out if there's a leak. I get the point of burping the heater core, like I said, I might still have air in there since it gurgling at start up. I'm gonna do it tomorrow once I change the thermostat..
 

Denisefwd93

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So how long should I have the system pressurized? I would think 10 minutes at over 16 psi should be plenty to find out if there's a leak. I get the point of burping the heater core, like I said, I might still have air in there since it gurgling at start up. I'm gonna do it tomorrow once I change the thermostat..
Hour/s Hot? Hour/s cold? , note the results, yes I understand you have to work for a living and your time is limited, that makes the problem even more difficult to solve.

Good luck!
 

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Thanks guys for the good info.
So yesterday I replaced the 190° thermostat with a 160° in the effort to keep the pressure down. Now the temperature won't go up to normal, it stays between the 2 cold marks way at the bottom, even after driving it for a while.
My question is, would running the engine that cold cause any damage? Will it stay on closed loop, affect gas mileage, mess up the O2 sensors, etc? I'm getting hot air out of the vents and seems to run normal, no check engine light. Should I put the 190° thermostat back? I just want to make sure I don't damage anything else. Thanks for the help.
Lower stat should be OK for short term, especially since we're getting into summer temps. My FSM (for my year) states open loop happens at 145*, but my scan gauge says a lot sooner. I have a digital temp gauge and found the gauge sender shows about 5-6* less than the ECT sensor. I have always struggled with low engine temps even with 195* stat - eFan has helped. Your gas mileage will suffer.

The 160 stat is not a solution as you know, but see what the glove test shows and remember to block the overflow connection for the test.

With lower stat are you still getting bubbles through overflow tank?
 

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I appreciate your comments. I'm not sure if the test kit I can rent will hold the pressure itself for that long, last time I used it I had a hell of a time getting it to work right, the rubber plunger thing in the pump kept coming off as I was pumping it so I don't trust it that much. Anyway, that's kind of a piece of crap when you have to put $268 deposit to rent the damn thing. I'll see what I can do tomorrow after work..
 

Rearanger

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I'm not sure if the test kit I can rent will hold the pressure itself for that long, last time I used it I had a hell of a time getting it to work right, the rubber plunger thing in the pump kept coming off as I was pumping it so I don't trust it that much. Anyway, that's kind of a piece of crap when you have to put $268 deposit to rent the damn thing.
is the kit testing pressure or using a changing dye color to show any exhaust in coolant?

I always put the deposit on credit card, so with return, charge never turns into cash payment.
 

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