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4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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Old 04-26-2015
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Head Gasket 1991 4.0 Ranger

My Ranger is a 1991 4.0 4x4 manual, with 202,000 miles. I am getting antifreeze in the combustion. I have suspected this for a while now as I am using antifreeze. For the last 2 weeks the ranger has not been started. When I went to start it, it wouldn't turn over all the way, like something was caught on the pulleys. Finally started and white smoke poured out of the exhaust, even water dripping some. I realize now it was hydro locking. Do you think any damage could have been done to the engine from that?

Is there anywhere else antifreeze could be entering the cylinders beside the heads? There is no water in the oil either. And recently I did a combustion in the cooling system radiator test with a liquid that is suppose to turn color if combustion is present in cooling system. It showed no combustion in cooling system.

I am trying to decide if it is worth it to replace the head gaskets and IF THAT WILL FIX IT. It is an old truck but I recently replaced the clutch and tires and it has adjustable rancho shocks and air bladdrs and a hitch. I always have a 1400 lb camper in the bed and still can get up to 20mph on road trips even with the mountains here in Colorado.

How many miles can I expect to get out of this engine? It has been well maintained with oil changes and never overheated since I have
owned it from 140,000 miles and first owner maintained it but no idea of him overheating or not.
Is there a chance it is just leaking in the intake manifold and not the heads or somewhere else?

So if I decide to do the head gaskets I will probably do the work myself and I have a few questions.
I was going to use a Felpro gasket set or do you suggest anything else like oem Ford or ??
Does it matter which brand of new head bolts I use? I see them really cheap on Ebay.
Wondering if I will need to do anything to the heads, how long do they usually last? Seems like it could get expensive to replace them.
Does anyone know how long replacing the head gaskets should take?
How about the lifters, push rods and rocker arms fuel injectors...do they usually have to be replaced?
Anything unforseen I might run into?
Any tips or suggestions or links about this job would be greatly appreciated.
Thanks for reading my long post.

Last edited by tekkatekka; 04-26-2015 at 07:41 PM.
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Old 04-26-2015
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Unless engine was running when it hydrolocked you didn't cause any damage, not enough force.

My '94 4.0l's bottom end is over 300k now, I cracked a head so they have been off.

Not a hard job at all, machine shop takes longest, lol.

Really doesn't read like a head gasket leak problem.
That ALWAYS causes overheating because cylinders 600+psi when firing pushes coolant out of the engine and into the overflow tank.

I would bet intake manifold.

What I would do is to get/rent a cooling system pressure tester, goes on rad cap and has a hand pump and gauge.
Drain some coolant out, below intake manifold height.
Unhook the coil pack wires, you want a no start
Pump cooling system up to 20psi, crank engine while watching gauge, if gauge needle bounces up and down then you have a cracked head or head gasket leak, you are seeing the 150+ compression going into cooling system.
If gauge just slowly drops then you have a regular leak, probably intake gasket because of while smoke.

Now remove all the spark plugs, and refill the cooling system(water is good), pump it up to 20psi again and crank engine.
You should see where the water is coming out, i.e. what spark plug hole
That will give you a better chance to see what failed during disassembly.


I have used Fel-pro in the past and will in the future, never had a problem over the years.

Good idea to replace thermostat at this time, 192 or 195degF is correct, not 180degF

Last edited by RonD; 04-26-2015 at 08:49 PM.
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Old 04-26-2015
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Quote:
Originally Posted by RonD View Post
Unless engine was running when it hydrolocked you didn't cause any damage, not enough force.

My '94 4.0l's bottom end is over 300k now, I cracked a head so they have been off.

Not a hard job at all, machine shop takes longest, lol.

Really doesn't read like a head gasket leak problem.
That ALWAYS causes overheating because cylinders 600+psi when firing pushes coolant out of the engine and into the overflow tank.

I would bet intake manifold.

What I would do is to get/rent a cooling system pressure tester, goes on rad cap and has a hand pump and gauge.
Drain some coolant out, below intake manifold height.
Unhook the coil pack wires, you want a no start
Pump cooling system up to 20psi, crank engine while watching gauge, if gauge needle bounces up and down then you have a cracked head or head gasket leak, you are seeing the 150+ compression going into cooling system.
If gauge just slowly drops then you have a regular leak, probably intake gasket because of while smoke.

Now remove all the spark plugs, and refill the cooling system(water is good), pump it up to 20psi again and crank engine.
You should see where the water is coming out, i.e. what spark plug hole
That will give you a better chance to see what failed during disassembly.


I have used Fel-pro in the past and will in the future, never had a problem over the years.

Good idea to replace thermostat at this time, 192 or 195degF is correct, not 180degF
Thanks Ron. I will try the pressure test. I do have a tester. I did a pressure test a few months ago without draining any antifreeze and it held pressure for at least 15 minutes...but it never hydrolocked like this before, so maybe it will show now. Whey drain coolant below int manifold height?
You are thinking it is the lower intake manifold is that correct? The gasket should show that when I pull it apart? If that is what it is would you bother taking the heads off? I have read a lot about 4.0 notorious for cracked heads. Could it ever be manifold and head gasket going bad on these?
Also I there a way to jerry rig the fuel injectors to fire so I can check them while the manifolds are off.
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Old 04-27-2015
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Quote:
Originally Posted by RonD View Post
Unless engine was running when it hydrolocked you didn't cause any damage, not enough force.

My '94 4.0l's bottom end is over 300k now, I cracked a head so they have been off.

Not a hard job at all, machine shop takes longest, lol.

Really doesn't read like a head gasket leak problem.
That ALWAYS causes overheating because cylinders 600+psi when firing pushes coolant out of the engine and into the overflow tank.

I would bet intake manifold.

What I would do is to get/rent a cooling system pressure tester, goes on rad cap and has a hand pump and gauge.
Drain some coolant out, below intake manifold height.
Unhook the coil pack wires, you want a no start
Pump cooling system up to 20psi, crank engine while watching gauge, if gauge needle bounces up and down then you have a cracked head or head gasket leak, you are seeing the 150+ compression going into cooling system.
If gauge just slowly drops then you have a regular leak, probably intake gasket because of while smoke.

Now remove all the spark plugs, and refill the cooling system(water is good), pump it up to 20psi again and crank engine.
You should see where the water is coming out, i.e. what spark plug hole
That will give you a better chance to see what failed during disassembly.


I have used Fel-pro in the past and will in the future, never had a problem over the years.

Good idea to replace thermostat at this time, 192 or 195degF is correct, not 180degF
I pressure tested the cooling system and turned the engine over and the needle stayed in one position. It took about 30 minutes for the gauge to drop 2 LBS. When I started the engine huge amounts of white smoke...
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Old 04-27-2015
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Good news

I would pull all the spark plugs, and see if you can find which cylinder is getting the coolant in it, spark plug will look Steam Cleaned, because it was.
Then crank engine and see which one is blowing "water" out
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Old 04-27-2015
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Quote:
Originally Posted by RonD View Post
Good news

I would pull all the spark plugs, and see if you can find which cylinder is getting the coolant in it, spark plug will look Steam Cleaned, because it was.
Then crank engine and see which one is blowing "water" out
I will try that. Still wondering if I should be concerned about the brand of
Head bolts to buy. I see very inexpensive ones on Ebay. Anyone have experience with them??
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Old 04-27-2015
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You don't need head bolts, but just get them from local parts store if you ever do, same with the Fel-pro gaskets
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