Mystery Coolant Leak, 1996 V6 Engine

Aug 15, 2014
8
0
1
35
Southern California
#1
Ok so, I'm sure this has been addressed already since it seems to be a fairly common issue, however I'm having trouble finding the threads.
Bought a 96 with the v6 engine recently, she had low miles, was in excellent condition and had no signs of the notorious blown head gasket issue. She's been driving like a champ and currently has about 86,000 miles under her. (Not a typo, not a new engine, everything stock. I got very lucky)
I just recently had an experience with an unexpected overheating issue. We replaced the cap and the bad thermostat, flushed the system, burped the air pockets etc. It ran beautifully for a few days, and then overheating again, this time I was able to turn the heater on and bleed enough heat off the engine to limp her home.
My problem is currently: she's been tested twice now at different shops, pressure tests beautifully, no visible leaking, no coolant in the oil, no anything. But I'm losing coolant. I've looked into it and am thinking it could be the upper intake manifold. Especially since I just replaced the alternator (which would have been rattling and pulling on the plastic manifold), and she's also running sluggishly.
Can anyone please tell me if I'm on the right track with the manifold, and where a good place to get one for not a million dollars would be? If not the manifold, what else could be causing my mystery leak, or where the heck is the coolant disappearing to?!
I know that was a long post, but thanks in advance for any input :)
 
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flstang65

10 Year Member
Dec 6, 2007
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#2
If it is the manifold, get the Ford Racing or OEM one with the metal cross over. DO NOT get the Doorman replacement. It will cost you horsepower and it is more of a universal type fit. Where are you losing coolant? in the overflow reservoir or the radiator it self?
 
Aug 15, 2014
8
0
1
35
Southern California
#3
If it is the manifold, get the Ford Racing or OEM one with the metal cross over. DO NOT get the Doorman replacement. It will cost you horsepower and it is more of a universal type fit. Where are you losing coolant? in the overflow reservoir or the radiator it self?
I'm needing to refill the radiator itself. Out of curiousity, why? Is it relevant or significant somehow? (And I forgot to mention in my post, please feel free to explain without "dumbing it down" because I'm a girl. I'm going to school for auto and I've got a pretty decent grasp of the workings of things) So be as technical as you need.
And thank you, I'll keep that in mind. I would be annoyed with a loss of power :)

Question, since I haven't had too much of a chance to poke around the engine on this one yet. Is it the manifold itself that fails, and how? Or is it just typically the gasket piece that fails? I know part of it is plastic, but I'm having a difficult time accepting that ford would use plastic for such a big and important piece in an engine that already runs a bit on the hot side... Lol.
 
Aug 15, 2014
8
0
1
35
Southern California
#4
If it is the manifold, get the Ford Racing or OEM one with the metal cross over. DO NOT get the Doorman replacement. It will cost you horsepower and it is more of a universal type fit. Where are you losing coolant? in the overflow reservoir or the radiator it self?
I forgot to mention. The overflow reservoir has maintained a pretty steady level of almost overfullness. When my coolant is down, it's always in the radiator.
 

Noobz347

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#5
I'm needing to refill the radiator itself. Out of curiousity, why? Is it relevant or significant somehow? (And I forgot to mention in my post, please feel free to explain without "dumbing it down" because I'm a girl. I'm going to school for auto and I've got a pretty decent grasp of the workings of things) So be as technical as you need.
And thank you, I'll keep that in mind. I would be annoyed with a loss of power :)

Question, since I haven't had too much of a chance to poke around the engine on this one yet. Is it the manifold itself that fails, and how? Or is it just typically the gasket piece that fails? I know part of it is plastic, but I'm having a difficult time accepting that ford would use plastic for such a big and important piece in an engine that already runs a bit on the hot side... Lol.

Yes. It absolutely matters. The fact that you're not losing it from the reservoir itself says a lot of things.

The very next thing that you need to do is pressure check your cooling system. If you have the tools, great! If not, take is somewhere and have them perform this inspection.
 
Aug 15, 2014
8
0
1
35
Southern California
#6
Yes. It absolutely matters. The fact that you're not losing it from the reservoir itself says a lot of things.

The very next thing that you need to do is pressure check your cooling system. If you have the tools, great! If not, take is somewhere and have them perform this inspection.
The system has been pressure tested twice. No abnormal results. It tests beautifully. Which is why it's so frustrating, because I'm certain I'm losing fluid somehow. But the leak isn't showing on a pressure test, or anywhere easily/readily visible to the eye both above and from under the vehicle.
 
Aug 15, 2014
8
0
1
35
Southern California
#8
Have you done a compression test of all of the cylinders?
That I'm not positive on, but I believe it was done the second time it was looked at. The first time was with a mechanic friend of mine and we covered all the basic tests. We also did a visual check on the oil, looks fine. No bubbles, no discoloration, no odd smells. The second time, it went to another trusted mechanic friend and he said he tested everything and he was totally confident that it wasn't a blown head gasket. And that everything tested beautifully. I apparently had been missing the plastic air dam from underneath the car near the radiator, it had gotten torn off somehow. So he replaced that, since he couldn't find anything wrong with the engine components. And it helped drastically. Matter of fact, it ran perfectly for about three days, until the coolant was low enough to overheat the car again.

Like I said, I'm pretty confident it's the intake manifold. I'm pulling it apart tomorrow to take a look at it (and hopefully fix the issue) if it's not that, then I'll take it to a dealership and cough up the $100 for a diagnosis at that point.
 

flstang65

10 Year Member
Dec 6, 2007
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94
SE Georgia
#9
Disregard my comment about the intake earlier, that applied to the V8. I did not see you had a V6. I would still look into the heater core also, has anyone actually pulled any of the spark plugs and looked down into the cylinders? If it is a bad head gasket or intake gasket then, the coolant could be getting into the cylinders and burning off.
 

Noobz347

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#10
...or do your air vents smell like coolant?


Regardless of all of that, if a proper cooling pressure test was done then it should have showed on the test. A leak in the intake should have showed up too.
 
Aug 15, 2014
8
0
1
35
Southern California
#11
...or do your air vents smell like coolant?


Regardless of all of that, if a proper cooling pressure test was done then it should have showed on the test. A leak in the intake should have showed up too.
I have a small oil leak, so the car generally smells like burnt oil, but I've not really noticed a coolant smell in the air vents, except for shortly after we mess with the system, or it gets overfilled etc.
and like I said, pressure tests totally normal. No visible leaking, no drop or change in pressure
 
Aug 15, 2014
8
0
1
35
Southern California
#12
Disregard my comment about the intake earlier, that applied to the V8. I did not see you had a V6. I would still look into the heater core also, has anyone actually pulled any of the spark plugs and looked down into the cylinders? If it is a bad head gasket or intake gasket then, the coolant could be getting into the cylinders and burning off.
I thought if the heater core went out my passenger floorboard should be wet and smelling of coolant.... ? We are taking it apart tomorrow to trouble shoot and run more tests. Including pulling the spark plugs and looking into the cylinders for anything visible.
Thanks :)
 

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