Quick summary of how I got to where I am and then the question: I've had my 2002 Ranger since 2006, bought it with 36k miles and it now has 215k. 4L V6 SOHC XLT 4x4. I was recently driving home from work and noticed the temperature started jumping all over the place, so I pulled in to a gas station and noticed the reservoir was empty. Topped it off hoping to limp home (still 40 miles away...) 10 miles in it's jumping around, I connect my reader and watch the temp go from 190s to slowly up to 230 for a mile or so then fall back to 190. I think maybe it's thermostat so I keep going, watching the temp as it goes up then down. Not smart, obviously. It finally over heated and I had to pull (stall) to the side of the road.

Tow to a shop, they say it's water pump and cracked thermostat housing. $1k to replace, but everything else looks ok. "they won't know for certain until they pressure test it". Get a call that it's a blown head gasket and another $3k to fix. I tell them nope and go pick it up. So it has a new pump, thermostat housing, sensors, etc and a blown gasket. I drove it home from the shop, it ran like ****, but made it home, a 2 mile drive.

All that to say this: I think I'm going to attempt the head gasket replacement myself. I have the space to store it while I work on it and it no longer needs to be a daily driver, just a lowes/errand truck. I'm an engineer by day, woodworker and DIY guy by night so I feel like I have the skills. I've replaced the fuel pump, alternator, done brakes, things like that on the ranger so I've got SOME automotive experience, but definitely no engine internals.

Any gotcha's I need to look out for while doing the fix? I'm thinking gasket kit, studs, machine the heads (unless they are flat, doubtful) or replace if cracked. Keep it simple. Do I need a timing tool?

Basically looking for any tips and tricks before I dive in. I figure I might as well, what do I have to lose...

 

Welcome to the forum

Very rare for 4.0l SOHC to blow a head gasket, never even read about a cracked head, 4.0l OHV engine did get cracked heads if over heated, totally different engine.
But since you are an engineer you can guess what happens to a softer material when it is placed between two EXPANDING metal parts, i.e. the block and heads while they over heat and expand
Thats what blows a head gasket, it gets crushed

Only "gotcha" is the timing chains on the 4.0l SOHC 1997 to 2004 had older design that tended to fail, if already updated then all is well

Cam timing is a big deal, of course, so check it twice then one more time, lol.

Head gasket failure can be IDed free, do a search for "Glove Test" on this site
simple easy test and 100% accurate
Can also ID where the leak is

 

I think the main gotcha for doing the head gaskets is; you are very likely going to need to remove the engine to do it. I think it is the right head that makes this necessary. It is extremely difficult to get to the rear timing chain without removing the engine. Yes, I am pretty sure you need the timing tool so you don't lose the timing when you remove the heads. I have not done this but am familiar with what is required to change the timing chains and cassettes because I expect to have to do this someday considering I have over 220K miles on my 4.0 SOHC.

 

If the heads are aluminum (I think?) and the block cast iron I could see that causing a nice little squish, haha. As suspected on the chains and I'm looking up the glove test right no. Thank you for the reply!

Not what I wanted to hear on the engine removal... if it comes to that I might just buy the engine lift from harbor freight. Like I said, I have the space (barely) to park the truck for awhile and work on it so I don't have much to lose besides time and money (hopefully keep the money loss low..).

All that said, just messed with the truck a bit after getting home from work, it has some odd behavior: 1. Oil looks fine and no water out exhaust. Cranks fine, idles fine, has what appears to be oil leaking on to the driver side exhaust manifold, starts to smoke after a few minutes where the oil is on the manifold. This leak has been there for about the last 30k miles... it's slightly worse now it seems. The weird part: I ran it at 2k RPM for about 1-2min... runs fine, temp comes up, then... it doesn't stop going up, it shoots up in to the 230s again... smoke increases and I kill it, obviously. So same damn behavior as the day it "died" This is with a new water pump, new thermostat housing, new t-stat. Why is it overheating still? There doesn't seem to be any obvious coolant leak, rad and reservoir are fine. Nothing under the truck, no coolant in exhaust...

Odd. Or I misunderstand the symptoms of a leaking/blown gasket...

 

Took the cap off the radiator, idled it for 3 minutes, replaced cap. Doesn't overheat now. Sits consistently at 175

I've got a misfire in cylinder 5 however...

 

Head gasket is OK

Pull out #5 spark plug and see what it tells you

You might do this first and then pull it out
Cold engine
Unplug Coil Pack's 4 wire connector, you want a No Start
Crank engine over a few times, count to 5 each time
Now pull out spark plug

Tip should be WET with fuel, if not could be fuel injector issue

But look at the tip and coloring to see what it tells you

 

Well that's good news, I think.

I will give this a try tonight! Thanks!

 

A cylinder needs 3 things to "fire"
1. Spark, at the right time
2. Fuel, in the correct mix with air(oxygen)
3. Compression, above 100psi, this is because liquid gasoline can't be ignited with a spark

Yes, the movie guys get that part wrong, lol, gasoline fumes are very very flammable, but not the liquid
Compression is HEAT, so the compression is needed to heat up and vaporize the gasoline that enters the cylinder so a spark can ignite it
You need about 30% vapor minimum in a cylinder for a spark to work, then the rest quickly vaporizes from the heat of ignition.

Cold engines with cold gasoline need to be "choked" for this reason, cold gasoline might only be 10-15% vapor depending on outside temps.
In the Carb days the Choke Plate was closed for cold starts so more gasoline was sucked out of the Jets, to get the minimum 30% vapor for starting.
Fuel injection computers have a Temp sensor, ECT sensor, computer adds more gasoline via the injectors for cold starts, so same as choke plate did for carb

 

Turned it over a few times, pulled the plug, wet with fuel. Cleaned it up, put it back in, no more misfire.

Idled it for a good 10 minutes, then about 3-5mins at 2k rpm. It started spiking the temp (230) so I shut it down. I cracked open the rad cap and it spit fluid / sucked air. Repeated the test again (idle then 2k rpm) and it stayed at 175. Repeated this 3 times, ran fine, temp stayed fine.

So... I'm not sure what to think. It definitely has an oil leak around 5 and 6. I think it's around the valve cover gasket, but not certain.

I'm thinking I might run it around the block tomorrow and see how it performs. Unsure why the shop was saying head gasket when I'm not seeing any signs of that now.

 

Put a balloon or glove over the rad cap opening, Glove Test
Start Cold engine
If balloon or glove inflates you have a leaking head gasket, period, very definitive test

All warmed up engines will spit out fluid and suck in air if you open the rad cap

Coolant expands as it is heated up, just like all fluids do, the point of the rad cap is to let the expanding coolant build up some internal pressure, usually cap is rated at 16PSI
This higher pressure raises the boiling point of the coolant

Water boils at 212degF, at sea level, at 5,000ft elevation water boils at 200degF, so less air pressure = lower boiling point

50/50 coolant/water boils at 230degF, at sea level

If there is 15psi of pressure added then 50/50 boils at 265degF, so the added pressure is a benefit

This is why you should never remove rad cap until engine coolant has cooled down to 0psi in the rad.

The reason a head gasket failure causes overheating is because when a cylinder fires, there is over 1,000psi in that cylinder pushing the piston down, thats what powers the crank/engine
Each cylinder is surrounded by coolant to remove the heat, so surrounded by coolant passages between block and head
If the head gasket around a cylinder fails it will let some of the 1,000PSI pressure leak out and into a coolant passage.
This pressure is AIR, well exhaust, lol, but in any case it ain't coolant.
The air displaces the coolant around the cylinder, and makes an air pocket in the head, this restricts the flow of coolant and engine starts to over heat
Rad cap will also get above its 16psi rating, so will open and warm coolant will fill up the overflow tank, when the air from the gasket leak makes it's way to rad it will go to the top and then it will flow out the rad cap to the over flow tank, and you will see bubbles coming up in overflow tank
People often confuse that with "boiling", while it is very hot, it is not boiling coolant, it is the air forced into cooling system from head gasket leak

 

Well damn, got around to doing the balloon test.

Tied a latex glove around the rad cap opening, disconnected coil pack, turned it over, glove immediately inflated. Connected the coil pack, removed the glove and left the rad cap off, cranked it for 2 secs, overflowing fluid.

Seems pretty definitive now on the head gasket being the issue.

If so, could the shop not have tested that prior to me spending $1k replacing the water pump?...

(why I went through all the other rigmarole before just trying the glove like you said in post 2, I don't know haha. Think I was scared of what I would find. Argh!)

 

Small head gasket leak wouldn't show up on Shop Tests, chemical test, if they did one.
Glove test is too "old school" for most shops to use, i.e they don't teach in mechanic school, lol, because it is too hard to charge for it

You can find out which cylinder is leaking using glove test
Remove 1 spark plug at a time and repeat test, coil disconnected
When glove stops bouncing last spark plug removed was from the leaking cylinder, put it back in to confirm.

You can use Rislone Head Gasket Fix or similar to seal the leak temporarily
Follow instructions.....very important
This won't hurt radiator or heater core, common myth mechanics like to use
It is a Liquid Glass that hardens at HIGH temps, 900+degF, so it seals the leaking cylinder only.

You must leave it in until you are ready to change the head gasket, because the seal will break away and re-seal over and over as engine metal heats up(expands) and cools down(contracts).

But it will get you back on the road

How long will it last?
I put some in neighbors engine, a POS worth the $30 for the sealer but not worth the $800 to redo the heads, lol.
He ran it for 3 years, he did change coolant and added another can of sealer after 2 years, eventually his transmission blew up, but head gasket was still sealed, lol.

 

Perfect. I only need it on the road for lumber errands so that should be ideal. The truck isn't worth much anymore so I was in the same boat, couldn't justify the expense.

I'll give the sealer a try and report back.

Thanks again!

 

It does work well, used it on many different motors over the years.
But it is a TEMP fix.

 

She lives! Gasket Fix sealed it up and it's running great. Will be a nice little lumber truck. Idle is a little rough, but it was like that prior to "the indecent". All other RPMs above idle are smooth as butter. Valve cover (or somewhere in that area) oil leak is a little worse than before, but not a huge issue. I might tackle that at some point, seems much easier than the head gasket replacement. Stays cool, no check engine lights, perfect.

Thanks again for the help!!

 

Good work

Thanks for posting the update