94 4L head gasket

[RonD]

1994 Ranger 4x4 4L, work truck, almost 300,000 km(Canadian), been a great work truck

Lost water pump about 18 months ago, I put a new one in and found I had coolant bubbling out of overflow tank and "that smell" in the exhaust.
Did a compression test and found one cylinder lower than the others.
Pulled the heads and one had a crack between the two valve seats, got a new head and sent both to a machine shop to resurface and pressure test, and new valve seals.

Put it all back together and it worked fine, for 9 months, then it started to mis-fire when cold, ran fine once warm.
Then it started to run hotter and was losing coolant, "that smell" again.
Compression test showed one cylinder was low, again, different side than last time.

Stripped the engine down to the heads and found one head bolt wasn't tight!!!???
I am getting older, but I don't think I could skip a head bolt, 4 times.
But it was not tight.
Pulled that head and put in a new gasket with new head bolts.
Engine was never overheated so I just cleaned up the head and block.

Put it back together and everything was fine.
9 months later, I am looking at the samething, started to mis-fire when cold, now bubbling coolant, and that exhaust smell.
But this time the compression test doesn't ID a cylinder.
I have
170
175
170

175
175
170

Spark plugs didn't help much either.
But as soon as you started the engine the coolant would start bubbling out with the radiator cap off, this was cold, closed thermostat.

I did test the block the first time, but just by using a straight edge and feeler guage, it didn't show any problems.

The timing of this is a puzzle as well, why the delay if there is a bad head, or block, or a "loose nut holding on to a wrench"(assembly issue).

I plan on taking the heads to the machine shop on Monday.
Maybe an exhaust port has a crack?
But is there enough back pressure in the exhaust to push coolant out at 15psi?

 

[RonD]

Just as a followup.

I did find a way to ID which cylinder was pushing air into the cooling system.
Not my idea but worked well without any extra cost or tools.

Latex glove test, lol.
Or balloon test

My cooling system was already drain but don't see why coolant would get in the way of this test.
I hooked all the cooling system hoses backup, heater and rad.
Blocked the overflow hose outlet.
Used a rubberband and latex glove inplace of the radiator cap(balloon would work as well)

All the spark plugs were out already, fuel pump was disabled as was ignition.

Then I just redid the compression test one cylinder at a time, putting a spark plug back in would work as well.

And sure enough on cylinder 6 that glove started to bounce, still showed 170psi on compression.
With the other 5 cylinders the glove didn't even twitch.
Retested #6 and glove started blowing up.

So I will pull that one head and see what I see.

Might just get this fixed today and back on the road tomorrow.

I am sure there are more complicated ways to do this, but this got me the info I wanted with what I had on hand.

 

[RonD]

Up and running.

I think I may have found the problem with the last two head gasket issues, we will see in 9 months.

I have a Craftsman Torque wrench, it is at least 20 years old if not more.
It has seen alot of use but not in the last 10 years.
This is what I used on the 1994 ranger heads.

You can test a torque wrench at home if you have a vise and some weights, I did such a test and ...............oh my.

Clamp the torque wrenches 3/8 or 1/2 inch drive in the vise side ways, so it is parallel to the ground.
Measure from the drive 12 inches down the handle and mark that spot, tape is fine.

Ft/lbs of torque is the weight(lbs) you are applying at 1ft(12inches)

so if you were to hang a 50lb weight at the 12" mark on the wrench, it should click if it is set to 50 ft/lbs, if it's set to 55 ft/lbs it shouldn't click.

Mine didn't, so I adjusted it up, and then up, and then up, if finally "clicked" at 68 ft/lbs.

So when I was tighting the head bolts to 59 ft/lbs as specified, I was really only tightening them to maybe 40 ft/lbs.
Then the 1/4 turn probably got me to about 60 ft/lbs

This is probably why they lasted a few months before they started leaking.

Since I don't wrench much any more I rented a torque wrench to do the head this time.
I also tested the rented wrench against mine and confirmed the 20lb difference at the 60 ft/lb area

 

[2813josh]

Hopefully it lasts this time. That glove trick is pretty cool,never thought of that. I guess it's like a McGyver leakdown tester lol

 

[shane96ranger]

That is a cool diagnostic tool. It makes perfect sense. I'm crossing my fingers that it's the last rodeo for you with the head gaskets too.

 

[RonD]

Yes, hope it is the last time as well.

Outside of the TOTAL FAILURE of my repairs I am getting pretty fast at taking the top end of this engine apart and putting it back together, lol.

Not counting the time to get parts, I am at about 4 hours from battery disconnect to start and test, without air tools.

But because of the TOTAL FAILURE I guess I could have got the same results if it only took me 4 minutes, lol.

"A poor workman always blames his tools"
In my case I am hoping it was the tool(torque wrench) that was what these failures had in common.

 

[alwaysFlOoReD]

Two great tools/tests to put in my arsenal, thanks Ron!
I guess its a little early for the 9 month review....but how are things holding up?

Richard

 

[RonD]

So far so good

 

[Andy D]

Great thread Ron. But all this talk about 4.0 heads cracking has me a little scared. My 4.0 runs fine and runs cool if anything. Will an over heat cause the cracking ,or is it just a bad head design? TIA

 

[84bluebronco2]

Makes for some good info there! I'm glad that I just have problems getting my Exploder to get warm, not the other way around lol. Hopefully I can get that sorted eventually

 

[RonD]

Never heard of a head cracking without over heating first.
It is just a thin point in the casting, between the valve seats.
Normal combustion temps are 2,000deg, when over heating it gets up past 3,000deg pretty fast and the top point of the cylinder gets hottest, where the valves are, so the most expansion of metal is at that point.

Run a 192deg t-stat to get engine temp up faster and hold it up.

Engines run best with coolant temps at 200deg to 220deg, best fuel economy and best lubrication, oil viscosity is measured at 212deg.

A t-stat doesn't set engine temp, a 180deg or a 192deg t-stat are both wide open at 200deg.

Using a 180 means the engine would have to warm up all the coolant in the system starting at 181deg, so engine will take longer to get to the 200deg operating temp.

Using a 192 means engine starts warming up all the coolant at 193deg.

Using a 180 t-stat on a cooling system designed for a 192 might mean the engine will run at 190deg or less, because of the cooling system size, especially in cold weather.

Most ford engines/cooling are designed for a 192 t-stat.

 

[adsm08]

The 6.4L Powerstroke cracks heads without overheating. I had one last year, 10 cracks in the head, around the valves, with no overheating at all.

 

[Andy D]

The 6.4L Powerstroke cracks heads without overheating. I had one last year, 10 cracks in the head, around the valves, with no overheating at all.

heh heh, so as long as the 4.0 doesnt diesel, I'm good
Bugs would get hot and seize or drop #3 exhaust valve. I never got a 360 AMC V8 hot enough to cause damage, same with the BMWs . I overheated a Datsun 1.6 to the point where it detonated through the piston and bent the rod. I bought a junk engine for the parts and got another 50 k out of it.

 

[RonD]

lol, OK as far as Ford 4.0l V6 heads, I haven't come across any that have cracked without over heating first.

What I read about the Ford 6.4 diesel head cracks was that is was much less of a problem than the 6.0 head cracks, lol, oops, another idea that was almost a good one.

I love Ford trucks, have tried others but IMO Ford makes the best truck in it class, but sometimes Ford needs to just let an idea go not build on it, trying to fix it.

 

[adsm08]

heh heh, so as long as the 4.0 doesnt diesel, I'm good
Bugs would get hot and seize or drop #3 exhaust valve. I never got a 360 AMC V8 hot enough to cause damage, same with the BMWs . I overheated a Datsun 1.6 to the point where it detonated through the piston and bent the rod. I bought a junk engine for the parts and got another 50 k out of it.

I slagged a VW 4-cyl once. My uncle checked and topped off the coolant before I took it, didn't get the cap on right, I hit the highway and took off, and she burned herself up darn quick.