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Old 08-04-2015
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Join Date: Aug 2015
Location: McDonough, GA
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Cooling System issues

Had my Ranger a long time, but brand new to the forum. So I have a 99 3.0 4x4 with 135k miles. Here is some back ground on the cooling system. At 87K the heater core went out and was replaced by a ford dealership. At 89K the heater core went out again and was replaced at a different dealership. At 94K the heater core went out again and was replaced by the same dealership that replaced the first . No cooling system issues until the water pump went out last summer at 121k. Replaced water pump and thermostat. No other issues until three weeks ago I had stopped and the truck had idled for a few minutes. I turned the truck off and about 5 minutes later i see steam bellowing out from under the hood. I pop the hood, but before I checked it out I turned over the key to see what the temp gauge said. The temp showed normal. I looked under the hood and coolant was boiling out of the surge tank. After about 20 min topped off the coolant and drove it home. Tried to recreate the issue at home, but couldn't. The radiator cap was old so I went ahead and replaced it. No other issues over the next two weeks while driving about 1k miles on a trip. Continued to watch without noticing any issues checking the levels daily. Went to put gas in the truck and decided to check it while I was fueling up, the surge tank was dry. I topped off the coolant tank again. The next day I drove 120 miles, checked the tank, no issues. Next day drove the same 120 miles, checked the tank, out of coolant. It had appeared that the surge tank may have overflowed while I had been driving. The passenger side carpet wasn't damp to the touch, but there was some moister on the bottom of the floor mat. I replaced the thermostat and temperature sender based on some conversations with people more knowledgeable than myself. I topped the system off again and let the truck idle for about a hour and a half. No issues that I could note. I have been checking the passenger side carpet, but still not damp to the touch. My wife drove about 100 miles yesterday and checked the levels when she was done, all looked good. This morning my wife went to drive, checked it, and found that the tank was empty. She topped off the tank and drove a few miles on errands. Got home coolant level was good, but now looks cloudy. I have been watching to look for signs of a blow head gasket (milky oil, bubbling in the surge tank from exhaust in the coolant, seeing if the coolant heats up rapidly) and can't find any. The truck hasn't overheated as far as the gauges read. Please help me with this issue!
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Old 08-04-2015
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one side of the engine cylinder head gaskets has failed

compression from 1 or more cylinders is pressurising the cooling system

IE::: coolant boiling out of the surge tank is a dead give away
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Old 08-04-2015
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Late '90's to mid-2000's Ford had problems with heater core failures across pretty much all models, cars or trucks.
Since you have replaced 3 I would say you have this problem.

Ford, of course, blamed it on cheap coolant, "poor quality" was the word used, lol.

But that aside, Ford started installing a flow restrictor in 1 heater hose to lower the flow thru the core.

The majority of repeat heater core leaks are due to high flow rate or use of poor quality coolant. However, electrolysis should also be checked, especially when repeat repairs have occurred.

If the heater core is leaking, review the location of the leakage and check the condition of the coolant.

Review the location of the leakage and check the condition of the coolant:
If leaks are found on the inlet (or outlet) tubes entering /exiting the heater core, it is most likely due to due to high flow rate - replace the heater core and install a restrictor in the heater hose closest to the engine block, reference Workshop Manual, Section 412.
If leaks are found in the body of the heater core itself, and does not appear to be the result of physical damage like contact or puncture, check the coolant for possible electrolysis.

Testing For Electrolysis

Check for voltage in the cooling system by touching the negative contact of a voltmeter to the battery ground or a known good ground and suspend the positive lead in the coolant, making sure it is in contact with the coolant but not touching any metal part of the radiator or cooling system. Both AC and DC voltages must be checked. Vehicles normally have DC voltages; however, a faulty engine block heater or faulty diode in the alternator can produce AC voltages. It is understood that coolant is lost due to heater core failure but try to obtain a voltage reading on the old coolant in the engine block before addition to or replacement of. To keep more coolant from exiting the heater core clamp off heater core lines and measure coolant in the engine block. Try not to dilute the original coolant with new coolant during testing if possible.

Determine whether coolant condition is acceptable.
Remove both cables from the battery and ensure they do not contact each other or the vehicle.
Touch negative lead of voltmeter to engine ground and positive lead in the coolant.

Check the voltage in the cooling system. If less than or equal to 0.4 volts (V) OK, reconnect battery cables and proceed to Step 2.
If greater than 0.4 V, flush cooling system thoroughly.
Recheck voltage less than or equal to 0.4 V.
Reconnect battery cables.
Refill the system with appropriate Motorcraft® engine coolant.

Check for loose or missing grounds at static conditions.

Turn off all accessories. Turn ignition on but do not start engine.
Test with ground probe to battery ground, engine ground, and vehicle ground sequentially.
Voltage less than or equal to 0.4 V on all grounds OK.
Any one greater than 0.4 V, check and clean ground cable connections.
Check accessories without using the on off switch on the vehicle instrument panel, use a jumper wire to ground.
Plug in engine block heater, if equipped, and test.
Recheck voltage less than or equal to 0.4 V.
Unplug engine block heater, if equipped.

Check for loose, missing, or inadequate grounds.

Test with ground probe to battery ground, engine ground, and vehicle ground sequentially.
Crank engine but do not start.
Monitor voltage while cranking. less than or equal to 0.4 V OK
If greater than 0.4 V, ground or repair starter.
Start engine and run at about 2000 rpm.
Turn on all accessories including those customer only uses occasionally such as CB radio, cell phone, etc.
Test with ground probe to battery ground, engine ground, and vehicle ground sequentially.
Voltage less than or equal to 0.4 V OK
If greater than 0.4 V, turn off one item at a time until V drops to less than or equal to 0.4 V. Repair ground to the accessory just identified.
Recheck voltage less than or equal to 0.4 V
Turn the DVOM to AC volts.
Check for ANY AC voltage greater than 0.4.
If any AC voltage is present then try turning off each accessory one at a time including blower motor and any fan motors.
If AC voltage is still present then shut engine off and remove B+ from the alternator and tape it up then retest.
If voltage drop is gradual to less than or equal to 0.4 V, the ground straps may simply be overloaded by added accessories. Test by using heavy gauge jumper to ground. If indicated, install heavier gauge ground strap(s) and recheck.

NOTE: If vehicle is equipped with electric cooling fans, be sure they cycle during this testing and monitor voltage when they are on and when off.


OK so that part is understood, now lets move on to the intermittent overheating and coolant loss.

Has the heat control or by-pass valve been replaced?
It is on the heater hoses it you have one.

Are the throttle body pre-heater hoses still hooked up?
Good read here on bypassing those: Ford Ranger Forum
Ford only used this pre-heat setup for a few years because it was not a great idea, lol.

The electrolysis thing is scary because it will eat up water pump blades so make sure you check that out.

Head gasket issue would cause instant pressure in the cooling system "usually" but this problem can seem intermittent when it first happens.
Cold engine
Remove rad cap
Start engine
let it idle, you may get a slight surge of coolant out the rad cap opening but it should stop within a second or two.
If it continues to surge then you have a blow head gasket.
If it settles down watch for bubbles at rad cap opening, smell the bubbles, exhaust smell would be bad.

Cold cooling system has no pressure, pressure in the cooling system comes from the engine heating up the coolant, and when you heat up a expands
Water pump is actually a water circulator, there is no "pumping", it creates no pressure.
When the coolant expands as it heats up the rad cap holds it in and system builds up pressure.
When pressure gets to 15psi the rad cap's large valve opens and lets some coolant flow out to the overflow tank, then large valve closes when pressure is down to 14psi(rad caps rating)
When engine is turned off, the coolant cools down and.........shrinks
So pressure in the system drops.
When pressure gets to -1 the smaller valve in the rad cap opens and coolant in the overflow tank is sucked back into the system.
So rad should always stay topped off.

If you ever take off the rad cap on a cold engine and coolant is not at the very top then this self-purging self-filling system is not working right.

Last edited by RonD; 08-04-2015 at 07:32 PM.
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Old 08-12-2015
Join Date: Aug 2015
Location: Wesley Chapel Fl
Posts: 1
How to Flush and add coolant

Check out this video for me if you need to know how to Flush your radiator, i just bought a 1999 ranger and im makin a couple how to videos on youtube, so all ya'll ranger fans out there if you could subscribe to my channel id appreciate that, im editing a video i made on how to to replace the fabric on the interior roof fabric with custom fabric of your choice right now and it should be up soon so keep posted, i attached some photos of how it came out in my truck.
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Cooling System issues-clu5iafwwaejw7v.jpg   Cooling System issues-clu5ixpw8aqrdir.jpg  
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Old 09-08-2015
Join Date: Apr 2012
Location: San Carlos, CA
Posts: 55
I had a similar problem in a 1980 Renault Le Car. Intermittent overheating, turned out the head bolts weren't properly torqued. Doing so fixed the problem.
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