Cylinder compression issue: Should I fix it or not?

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stylo328

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Hello all,

I have a 2004 TJ with a 4.0 and six speed. Last week the idle was pretty rough so I decided to change out the spark plugs (even though they were fairly new). I found the plug on cylinder six fouled. I couldn’t quite explain it but I put the new plugs in, cleaned the throttlebody and started to drive out of the neighborhood. The idle got progressively rougher so I drove it home and had it towed to the shop.

Today I received a call that compression on cylinder six is down in the 100 range while the other five are in the 150+ range. When they tested the compression on cylinder six the radiator hoses got very hard. The mechanic believes it’s a blown head gasket. I was quoted $1,700 for the repair and that is not including a replacement head if necessary. The jeep has a decent frame and average body and decent interior. I’m struggling with whether or not to fix it. I would really like the thoughts of the group on what you would do if you were in my position.
 
Sounds like a head gasket to me.

Why wouldn't you fix it? If you sell it with this issue, it's going to be a much harder sell.

If I was in your position I would fix it, no questions asked.
 
Thanks. I will ask the mechanic about hat tomorrow. That said, if it is in fact the head gasket, is $1,700 a reasonable cost for that repair?
 
$1700 sounds high for a head gasket job. Its a cam in block straight six with good access. Whats the labor rate at this shop?
 
X2 on a leak down test. They pump a calibrated flow of air into the cylinder and see where it's leaking out. Rings, valves, head gasket, etc. The comment about the rad hoses getting hard points to a cylinder leak into the cooling system, consistent with a head gasket and/or head crack.

We don't know your level of mechanical skill with wrenches, but a 4.0 is one of the easier engines to do a head gasket on. But it also depends what it needs when you get in there. If it just needs a gasket and cleaning the mating surfaces then it's the cost of a gasket set, head bolts, oil and fluids. Burnt valves or warped head needs a machine shop resurface and then recheck for pushrod length. Cracked head would need a replacement head. Warped block or leaking piston rings is much much more involved (but less likely). Does the $1700 estimate include any problems they might find such as a cracked head?
 
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What is the flat rate hours for just a head gasket? $1700 sounds expensive to me. I'm purely guessing 4-6 hours at a Jeep dealership. I am also out of touch with USA hourly shop rates. A quality completely rebuilt engine with a warranty could be bought for $1700.00 How many miles on the rig? If the problem is only in top end or gasket, you could pull the head, have a machine shop freshen it, and reinstall it yourself without too much trouble.
 
The $1,700. price sounds more in line with having the head re-built and installed not just a replacement gasket. My son and I replaced the gasket on his XJ starting about 8 in the morning and finishing up around 3 in the afternoon and I would hardly call it intense.
 
I'd say $1700 is steep, but the cost of running a competent shop these days is getting pretty insane, so that may be the going rate. If it's as simple as just a head gasket, I'd say up to $1000 would be fair at a good shop. The thing is though...a good shop won't just pull the head and replace the gasket. They'll send the head out to a machine shop to be cleaned and checked for cracks, and since it's off...very likely they'll get a valve job and possibly have it resurfaced as well, to cover their ass and make sure it stays fixed.

The way I fix my own vehicles and the way I fix customer vehicles are very different....I don't mind taking some calculated risks when I'm the only one that will get mad at me when it doesn't work...more often than not, this approach is not acceptable with a customer vehicle.
 
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Thank you all. The $1700 estimate includes a $200.00 allowance for any machining of the head or small crack repair. Engine has 178,000 miles. it needs a new oil pan cover as well. That is where my trepidation lies. Will I be starting a cycle of throwing good money after bad. Maybe a rebuilt engine is a smarter option?
 
stylo328 said:
Will I be starting a cycle of throwing good money after bad. Maybe a rebuilt engine is a smarter option?
Click to expand...

This is a great question to ask and the answer is possibly. 178k isn't scary mileage for a 4.0L engine. The slippery slope is replacing parts while they're doing the work. For example, if the oil pan has to be replaced, that's also the time to replace the the oil pump and rear main seal (RMS). While doing the headgasket, if it hasn't been done, that's also the time to replace the entire cooling system (radiator, hoses, waterpump, thermostat, pulleys, etc.). The cooling system is independent of repalcing the engine, but the oil pump and RMS are not.

All that said, only you can decide if the Jeep is worth keeping. If you're the type that's risk adverse, sell the Jeep and move on (Option 1below). If you think it has value, and are willing to accept the risk, your choice is then between options 2, 3 and 4 below. If it were me, my choices would be either option 2 or 3, dependent on what the leak down test says. In either case, I'd be prepared to spend more than the quoted $1700 to address the issues I mentioned.

1. Cut you loses and sell the Jeep like it is
2. Fix your head and headgasket
3. Get a re-manufactured head installed
4. Install a new engine
 
Shop rates around me are in the $115 to $140 hourly. So that makes it a 2 day job to replace a head gasket. That seems long even for someone doing it In their driveway. The problem comes with detecting why it happened and how to prevent it from happening again. This is the part that a normal guy has problems. You can't magnaflux the head, check for valve guide wear, etc. When an engine is bumping 200,000 miles it is a tough call if it has another 100,000 on it. If the engine is problem free that is one thing, but your engine may (or may not) be on the verge of new bearings, oil pump, maybe a new crank? It's a guessing game at this point. I'd be looking into a replacement engine. What would that cost? And with warentee? Either way it is cheaper than a new vehicle. And a used vehicle in a similar price range may have all sorts of problems that will run that cost up quickly.
Shop around for a different shop and see what they charge. But in the end it will be your best guess of what to do.
 
Thank you all for your thoughts. How difficult would this be to do at home. I’ve got a descent collection of tools and I’m sure I could find a machine shop if necessary. I’ve never done a head gasket before though. Would you attempt it if you were me?
 
stylo328 said:
Thank you all for your thoughts. How difficult would this be to do at home. I’ve got a descent collection of tools and I’m sure I could find a machine shop if necessary. I’ve never done a head gasket before though. Would you attempt it if you were me?
Click to expand...

Most mechanical automotive repairs are more intimidating than anything else. It's just nuts and bolts, with some attention to detail mixed in.

The main issue here is determining why you have low compression....someone told you a possible reason, but you have to validate that once the head comes off, by inspecting the cylinder walls, headgasket, and cylinder head.

Based one what you've already posted...I'd make sure the radiator cap is good...or go spend $9 on a new one, run the thing around for a bit until it's good and hot, then park it and let it cool. First thing after it cools, pull the plug on the cylinder suspected of pressurizing the cooling system and run the crank around until you can see the piston through the spark plug hole...do you see coolant too sitting on top of the piston? We need to confirm the diagnosis as best we can before you start the teardown...because it's often more difficult once everything is apart.
 
If I suspect a bad head gasket I start looking for oil in the coolant and coolant in the oil. With a cold engine pull the radiator cap and look for oil floating on top. You can also use a turkey baster and pull a sample. With a warm engine pull the dipstick and see if the oil looks like a milkshake.
I agree with PatMc that most mechanical automotive repairs are more intimidating than anything else. It's just nuts and bolts, with some attention to detail mixed in.
 
Like they said, if you can change a water pump you can rebuild an engine. It's a matter of faith in you and having the proper tools. Until something goes wrong. Broken studs can make an easy job nearly impossible. But worse case scenario on a head job is you might need to replace the head. And that may be what you need anyway. First I would validate the compression test. A tester is cheap to buy and easy to use. A bad head gasket will normally either push oil into coolant or coolant into oil. Normally. I have seen several blown gaskets that do neither. And a cracked head may do neither too. It all depends where the gasket is leaking. So confirm the compression. If this isn't your daily driver and you have an indoor place to do it then you can save a lot of cash doing it yourself. But you have to be organized and label everything you remove. Take a pic of every step to be sure you don't miss anything and be analy clean and neat.
Other than that, it's a piece of cake. I rebuilt my first (tractor) engine at 10 years old. That was in the '70s. And it's still running today. So it can't be too difficult. I leaned to really love working on machinery at an early age. It's never too late to learn a new love.
 
I would do it yourself...it is not your DD and if you get in over your head you will only end up in the same position you are in now...paying a shop (OK maybe a tow also). Go for it, it will be so satifying to accomplish this and know you saved a grand or more.
 
All good points here. If you have even average mechanical ability and a basic set of tools resources there isn't any reason you can't tackle it yourself. It might take you a bit longer, but between this forum and YouTube there are tons of resources to help you along the way.

I also agree that the $1700 quote seems a tad steep. Like others have already pointed out you're getting into the price range of a rebuilt engine with a warranty.
 
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