Head gasket or worse?

[Ruffian1911]

I have a 98 TJ with a 2.5l with 149k miles.
I have all the symptoms of a blown head gasket. Overheating, unexplained loss of coolant, white smoke from exhaust, milky substance on bottom of oil filler cap, and overfill of the oil on dipstick (not milky). I did a compression test:
1 153 psi
2. 129
3. 68
4. 109
Do these readings indicate something worse than a blown head gasket?

 

[Link]

Definitely a bad head gasket. No real way to know for certain on the rest of it. If you have a scope you could run it down the spark plug holes and check things out and see how the cylinders look.

 

[Ruffian1911]

So I took the head apart and found where the gasket failed. Brought the head to a reputable machine shop who told me on the phone that they will degrease and mill it for $150. When I got there he asked me how many miles on it and then suggested that I also have a valve job done for $300 for everything. Any suggestions on what I should do?

 

[JustDandee]

When I did a 2.5 in my CJ. I asked the guy to mill a little aggressively looking for the slightly higher compression bump. It does not move the needle a lot but it was noticeable all through the rpm range, it just zipped around better. If I had the dough, do the valves, new seals. Your there and the payoff comes as you get over the 200k mile mark, it will still be running like a new motor.

 

[Link]

Do the entire head completely. It's worth the extra money.

How do the tops of the pistons and cylinder walls look?

 

[Ruffian1911]

Do the entire head completely. It's worth the extra money.

How do the tops of the pistons and cylinder walls look?

They look good. I called the shop this morning and told him to do the complete job. Price is $295 for everything

 

[TJ Jim]

They look good. I called the shop this morning and told him to do the complete job. Price is $295 for everything

Good decision!

 

[MutantNinjaTJ]

They say not to put a new head on an old lower, it will blow through the rings due to higher compression on top. Never tried it, always rebuilt the whole motor at that point.

 

[Danarch]

I think it is well worth it.

 

[Link]

They look good. I called the shop this morning and told him to do the complete job. Price is $295 for everything

Sounds like a good price to me. Smart decision!

 

[Link]

They say not to put a new head on an old lower, it will blow through the rings due to higher compression on top. Never tried it, always rebuilt the whole motor at that point.

I've rebuilt a few heads on old engines and never had any issues. I could see potentially a little more blowby on an older engine vs a new or rebuilt one but realistically, the per cylinder compression difference between an old head and a rebuilt one won't be a lot. It'll be a lot in the OP's case because his head gasket was damaged/gone already but if you had a higher mileage engine with a good head and head gasket, if you pulled it, rebuilt the head, and reinstalled it, you won't have much compression difference realistically.

 

[tr21triton]

They say not to put a new head on an old lower, it will blow through the rings due to higher compression on top. Never tried it, always rebuilt the whole motor at that point.

 

[Potomus Pete]

Now I'm scared. I have a new head going on a motor, well taken care of with 136K. Am I going to have trouble with the bottom end.

 

[tr21triton]

Now I'm scared. I have a new head going on a motor, well taken care of with 136K. Am I going to have trouble with the bottom end.

Nope you should be just fine. Just like the OP. If anything you will be happy happy happy because if your head and/or valves were the issue it will be fixed and you SHOULD notice better performance. There's no need to rebuild the bottom end unless there was a problem with it in the 1st place IMHO. the new head and valves are not going to put any more pressure on the lower end than it is designed to take, unless you had a large amount shaved down to increase compression. The same point link is saying

 

[Potomus Pete]

Thanks I'm about to put this Clearwater head on thats in my garage. . I have a 2.5, and I'm nervous considering I have never done one before. It seems too easy to be true compared to a Ford 302.

 

[Link]

Thanks I'm about to put this Clearwater head on thats in my garage. . I have a 2.5, and I'm nervous considering I have never done one before. It seems too easy to be true compared to a Ford 302.

Just do it. A long journey begins with a single step. EVERYONE who works on vehicles/equipment/mechanical stuff had to start somewhere. EVERYONE who repairs things has messed something up at some point. Don't be scared of it....youtube is your friend. I wish I had youtube when I was first starting out repairing stuff.....I would have made fewer mistakes!

 

[tr21triton]

Just do it. A long journey begins with a single step. EVERYONE who works on vehicles/equipment/mechanical stuff had to start somewhere. EVERYONE who repairs things has messed something up at some point. Don't be scared of it....youtube is your friend. I wish I had youtube when I was first starting out repairing stuff.....I would have made fewer mistakes!

agreed, just print out the installation procedure (available in service manual under resources here) and torque the way it says to. you'll be fine.

 

[JustDandee]

Honestly the concern of a swapping in recondition head on high mileage lower - probably applied more back in the day when 100k miles was a lot for an engine. Materials and process have improved that at the mileage y’all are indicating it would not concern me a bit.

 

[BlueC]

There is zero issue with putting a new or rebuilt head on an existing bottom end. The bottom end is either in good condition or it isn't. The new/rebuilt head will not magically wear the rings/cylinder/bearings.

 

[TJ Jim]

Just do it. A long journey begins with a single step. EVERYONE who works on vehicles/equipment/mechanical stuff had to start somewhere. EVERYONE who repairs things has messed something up at some point. Don't be scared of it....youtube is your friend. I wish I had youtube when I was first starting out repairing stuff.....I would have made fewer mistakes!

First engine I rebuilt I went step by step by a chilton’s manual. There was no internet or YouTube to follow. It ran great from startup to when I sold it 55,000 miles later. Being a brave soul and young and not real smart the day I started it I drove it 600 miles to visit family and it never missed a lick.
These days I’m not sure I’d trust a Chiltons rebuild