Cracked cylinder head symptoms

[Tech]

This is just an FYI post: Several months ago I noticed that my '91 Explorer was using about 1 cup of coolant per week. There were no indications of any external leaks and the oil level seemed to remain constant; at least, it was not increasing. Also, the oil never appeared to be contaminated. Eventually, I noticed a small amount of moisture on the underside of the oil-filler cap and PCV valve -- bad sign. So, I pulled both cylinder heads. I couldn't see anything wrong with either head so I took them to a specialty shop. They found that one head had an internal crack in one of the passages and it was junk (not repairable).

Since I am really happy with my Explorer and plan on keeping it indefinately I decided to replace both heads with factory-new units. It's note-worthy that the replacement heads are for a '93 or '94 Explorer and are allegedly improved over the crack-prone '91 heads. I also used all new Ford gaskets as they are of an improved design over the originals (no more leaky valve-covers!)

My Explorer had 97k miles when the coolant problem reared it's ugly head. Also, it was using about 1 quart of oil every 3000 miles, which really isn't bad. Interestingly, since I installed the new heads, the oil consumption has gone down to about 1/4 to 1/3 quart every 3000 miles. Apparently, the valve guides and/or seals were worn. Another bit of good news you Explorer fans will like to hear is that the cylinder walls looked like new, even after 97k miles -- there was absolutely no ring ridge! Even the factory cross-hatch was still visible! I guess changing the oil every 3k miles has paid off.

If anyone is planning on removing the cylinder heads on their Explorer (the standard, 4.0L pushrod engine) and would like some details on what's involved, please feel free to e-mail me.

[This message has been edited by Tech (edited 08-17-1999).]

Dave - Thanks for the great post. Good info to file away for future reference. My '91 has 145,000 miles and I am fanatical about keeping the engine cool since there are so many stories out there about early Explorer cracked heads.

(non-Explorer content follows...) I also appreciate your webpage. It is very well-written. I was eight and nine years old when you were in Vietnam. My older brother missed the draft by only a few numbers when they stopped calling guys up. I remember making Christmas cookies and stuff and packaging them up to send to the guys in Viet Nam. I also distinctly remember seeing film clips of the war on the evening TV news and thinking that the audio I was hearing (gunfire etc.) was nothing at all like the war movies. Your points about broadcast media/Hollywood distortion of reality is well-taken. Welcome home! And thanks for your service.

Pete Chandler
Bakersfield
'91 4x4 4dr XLT

[Mike 92 XLT]

After a drive, should the underside of the oil filler cap be completely dry? I took a look at mine yesterday after coming home from work, and it was wet, but when I wiped it, it was brown like oil.

thanks

Mike
92 XLT 4x4

[This message has been edited by Mike 92 XLT (edited 08-10-1999).]

[takao]

I've sent my 92 to the dealership while it was under warranty they told me the leak was the gaskets, new gaskets went in, then the other two times they said the radiator cap was bad. My coolant leval drops a bit every month but no coolant in the oil no coolant on the ground. I always thought it was funny that my exhaust pipe was always clean "no grey residue" thanks for the information. due you know if newer version heads fit?

[srwilson8074]

I have a 94 explorer and I need to replace the intake manifold gasket, does anyone have experience with this and should I replaced the heads? I do not want to go through the process of replacing intake gaskets and finding heads are shot. Waiting to get a presure test done. is there anything I need to keep my eye open for?? any help would be appreciated.

[Burns]

Little tip for you since your a new poster.

It looks like you used the search but you posted a reply to a thread from 1999. I highly doubt that there will be any reply to this thread now.


Happy Searching

[Tech]

Originally Posted by srwilson8074

I have a 94 explorer and I need to replace the intake manifold gasket, does anyone have experience with this and should I replaced the heads? I do not want to go through the process of replacing intake gaskets and finding heads are shot. Waiting to get a presure test done. is there anything I need to keep my eye open for?? any help would be appreciated.

It's been a long time since I did the job, but I think there's several gaskets involved with the intake system. There should be 2 gaskets on the lower manifold where each side mates with the left and right cylinder head. Also, there should be one gasket between the upper and lower intake manifold (the manifold is 2-piece. This of course, is assuming you have the standard 4.0L pushrod engine, not the overhead cam engine.

As to your cylinder heads, replacing them (which is a bit of work) depends on symptoms. Compression OK? Loosing coolant (cracked head). How many miles are on the current heads?

If the compression checks out good on all 6 cylinders and there's no evidence of coolant leaks, I wouldn't worry about the heads too much.

Best of luck!

Tech

[srwilson8074]

Tech,
Thanks fo rthe information. I work on older cars but for some reason the newer cars scare the heck out of me. I want to put dye in the coolant and see if I can pin point the leak. I know that it leaks behind the AC bracket, this is just by adding coolant. This truck holds a lot of sentimental value, it was given to me by my nephew and it is in really good shape. Mileage on it is 124,360 mile. It has been maintained very well. Other then the h not being able to find a headlight switch for a 94 limited with auto darkning mirrors this truck is great. I appreciate your quick response and your help, hopefully I can repay the favor someday. Thanks so much Steve.

[Tech]

Originally Posted by srwilson8074

Tech,
Thanks fo rthe information. I work on older cars but for some reason the newer cars scare the heck out of me. I want to put dye in the coolant and see if I can pin point the leak. I know that it leaks behind the AC bracket, this is just by adding coolant. This truck holds a lot of sentimental value, it was given to me by my nephew and it is in really good shape. Mileage on it is 124,360 mile. It has been maintained very well. Other then the h not being able to find a headlight switch for a 94 limited with auto darkning mirrors this truck is great. I appreciate your quick response and your help, hopefully I can repay the favor someday. Thanks so much Steve.

Sometimes an external coolant in the cylinder head area is caused by a bad head gasket. The cracked head on my Explorer was completely internal, so there was no visible coolant on the engine.

Pulling the heads involves unbolting the AC pump (not the lines) and carefully moving it to the side. I suspended my AC pump from the hood with a small rope, being careful not to put any unnecessary strain on the AC lines. There's quite a few electrical connectors to deal with as well, but if you label them and/or take pictures you should be OK.

You'll need some metric wrenches, a torque wrench, as well as some big torx sockets for the head bolts.

-Tech

[srwilson8074]

Thanks again, will a system pressure test reveal a crack in the head if it is internal? Should I get the head magnafluxed? What is the difference of new heads and rebuilt, is there a new design with thicker walls?

[Tech]

Originally Posted by srwilson8074

Thanks again, will a system pressure test reveal a crack in the head if it is internal? Should I get the head magnafluxed? What is the difference of new heads and rebuilt, is there a new design with thicker walls?

I'm not sure what the procedure is for testing the heads for cracks. It could very well be magnaflux. In my case, I just got bold and pulled both heads and took them to a shop that specializes in cylinder heads. The crack was in the #5 cylinder head area and was not repairable. From what I found, early Explorers were prone to cylinder head cracks, so I opted to replace both heads with factory new assemblies, even though the other head checked OK. I did not want to do this job again. The new heads are improved and are not prone to cracking like the earlier versions. I bought "complete" head assemblies, in that they had new valves and springs already installed. I bought all the parts from Ford. As I recall, the new complete heads weren't that much more expensive than rebuilts.

I also bought a complete upper engine gasket kit which was also much improved over the originals. It included not only new head gaskets, but also the complete intake manifold set and valve cover set. The valve covers were always prone to leaking oil and the new gaskets cured that problem completely. So when I was done I had a leak-free engine!

A side benefit to the new heads was reduced oil consumption. My Explorer had about 97,000 miles on it and I think it used about one quart of oil between changes. Not bad, really. But after I replaced the heads the oil consumption went down noticeably. I believe the oil consumption was due to worn valve guides and/or worn valve seals, which can cause increased oil consumption.

When the job was done, the engine ran like new and continued to do so until I sold it at around 125,000 miles. It was a good engine.

-tech

[srwilson8074]

I think I will rsource a new set of heads, I would rather take it apart once and for all and do it right. The truck get about 18 mpg which I don't think this is bad. The truck is very comfortable so I think it worth it. Thanks again for all your help.

>steve

[wolstrading]

I am planning on redoing my 05 explorer . I find the oil looking milky in the dip stick and it took about 4 bottles of coolant. What do I do pls? How do I begin?

[35Remmy]

WOLS, if your oil is milky, I would advise on NOT driving it!!! You'll destroy that motor FAST!!!

[35Remmy]

Also, I've always been told that it's a bad idea to put new heads on a high mileage engine because the higher compression is too stressful on the bottom end.

If I were replacing heads, or head gaskets for that matter, I would definitely go with new lifters...however, isn't it a big no-no to break in new lifters on the old camshaft? So a new camshaft to match the new lifters would be necessary, wouldn't it?

[Tech]

Originally Posted by 35Remmy

Also, I've always been told that it's a bad idea to put new heads on a high mileage engine because the higher compression is too stressful on the bottom end.

If I were replacing heads, or head gaskets for that matter, I would definitely go with new lifters...however, isn't it a big no-no to break in new lifters on the old camshaft? So a new camshaft to match the new lifters would be necessary, wouldn't it?

Replacing the cylinder heads with new, factory stock heads will not raise the compression. It might restore the compression to factory specs IF there was leakage in the cylinder due to a bad head gasket or leaking valves. About the only other thing that will cause the compression to drop is worn piston rings and/or worn cylinder walls.

As to "stress" on the lower end, there's no reason why the lower end couldn't live up to a healthy top end unless the main and rod bearings are shot. Typically, those bearings go can 200 thousand miles or more and still function properly.

I replaced the heads on my '91 Explorer at about 98,000 miles and the cam and lifters looked like new. I pulled each lifter and examined it and the corresponding cam lobe. Also, the lifters had roller bearings riding on the cam, so there's no a "break-in" issue.

-1.3L

[srwilson8074]

If I might add that its an old wives tale about replacing new heads on an older bottom half. The pistons make the compression after it reachs its top stroke. The newer valve seating will make sure all the cylinders do not have any leaks and the compression should beclose as long as there is no problems with the rings and pistons. "If the motor had been smoking and knocking in the bottom end then I would not recommend it"
I have a couple of question and maybe I could give some advice.
Did the car over heat and was it driven for a long period of time overheating?
Did you notice white smoke coming from the exhaust? There are a couple of simple things you can check yourself without spending a lot of $$$$$$$$.
Did you pull any plugs and check to see if you have traces of coolant?
Try to get the piston as close to top as you can, take a medical swab and insert this in to the cylinder and see if there is any anti-freeze, that will help eliminate any questions if the head gasket is leaking into the cylinder also.
Did you see any traces of coolant on the plugs?
When the vehicle is running do you have white smoke coming from the exhaust? Is there a sweet smell evident when the vehicle is running?
If you are fortunate the gasket is only leaking into the oil return port, "NOT" saying this is great but it leaves less chance of scorching the cylinder walls.
Pressure test the system and watch the gauge, remove the oil fill cap and put your ear over the hole to see if you can hear a hissing or leaking sound.
Milky oil is a sure sign of coolant in the anit-freeze, if you don't have to run the car I wouldn't.
Once you have the heads removed, I would take them to a good machine shop and have them check the head for warpage, you can do this yourself also with a straight edge, laying it across the head moving it ever so slowly and watching to see if you can see space that is different fron one side to the other. "AFTER THE GASKET HAD BEEN REMOVED sorry" Water test where the valve seat.
Turn head over so the bottom is facing up, put a little waterin each port and watch to see if it leaks, if not valves are seating good.
Remove the water with a rag or sponge, air dry the put a little Marvel Mystery oil to ensure they do not have a chance to let rust to start.
Check the pistons the same way but with a light guage oil.
Feel the top of the cylinder wall and check to see if there is a ridge, any scratches from top to bottom, slight cross etching is fine.
If all this checks out fine, I would buy a quality gasket set and new head bolts, some engine manufactures recommend that when you change the gaskets, change head bolts also.
Torque the bolt in sequence, tighten them with a torque wrench and bring the bolts up to the called for spec.
Please pre match gaskets with the old ones making sure all the openings in the gasket match the ones on the head.
Don't forget the RTV on each of the four spots where the plenium and heads meet. Just use a little and let this set up for a couple of minutes and then remove excess from the motor once it drys.
Hope this helps sorry if it is long but I wanted to try to help with as many steps as I could so you wouldn't worry about them.

[35Remmy]

I must have had a pre-exisiting problem then because my '93 wrangler was experiencing blow-by at 150,000 miles (2.5L slug) and running a little rough.

Had the head rebuilt, slapped it on, started it up, and she ran like a sewing machine for about 2 days...until the blow-by got SO bad it filled my air filter box...took the head back off...cylinder #3 was gone. Rings broken, crown chipped, skirt scored. Game over!!!

Funny thing is my father told me not to do a new head because the motor had a lot of miles on it. Heh. Should of listened to dad. In this case, it certainly wasn't a wives tale!!!

Like you said, though, there was obviously a wear problem to begin with with the blow by.

[wolstrading]

Thanks dude, It is at the shop now.

[srwilson8074]

Sorry if the information I offered was not what you thought it should have been, i was commenting on my experience with cars over the many years I have worked on them. I hope your cars turns out fine