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Head Gasket replacement

Hi everyone!

I have a 2001 NIssan Sentra GXE with 125,000 miles on it. I recently took it to my mechanic because the car has rough idle( one time it started shaking violently while at a stop light). Well to make a long story short, he did a compression test which came back that I had 140 pounds of pressure in cylinder 2 and 3 and cylinder 1 and 4 were fine and that the head gasket needs to be repalced. The cost 1000 dollars. I told him I would get back to him. I don’t know what t do, this is my first car, I 've had it for two years and have had no major issues with it. Part of me wants to get it fixed but the people I’ve talked to say replacing the gasket is like opening a can of worms. I could purchase another used car but that will eat up all of my savings and I am not sure I am comfortable with that.

Before committing to an expensive repair, you owe it to yourself to get a second opinion.
And then, if the second mechanic also states that you need a new head gasket, see how much he would charge for it. $1k for head gasket replacement on an I-4 engine is rather high–unless other repairs are included for that price.
Is that $1k quote for just a head gasket replacement?

As to ditching this car and buying another used car, think about this:
The “new” used car will likely be a mass of unknowns regarding its overall condition and its previous maintenance.

Your “new” car could wind up needing expensive repairs, just like the one that you have currently. If you have maintained your current car at least as well as Nissan specifies, and if all other systems of the car are in good condition, I think you would be better-off repairing the known quantity, rather than buying an unknown quantity.

I agree with VDCdriver. Don’t ditch the Sentra because of a bad head gasket. Get that second opinion because a $1k quote is in the high end of an estimate for this job. The Nissan Sentra GXE is a very good vehicle if properly maintained.

I third the motion. 140 lbs does not sound too low to me. $1k sounds too high. You may have another problem, but I think you need another mechanic first.

Yes! The price he quoted me is for the gasket replacement plus whatever work needs to be done in relation to the gasket. Intially he would have charged me 1300 but I had a tune up done 3 weeks prior(they initally thought that was the problem), he would only charge a grand if I paid cash.

Also, I did call another mechanic, he also stated that 140 didn’t sound too low and that I should take it to a nissan dealership for a second opinion.

“He would only charge a grand if I paid cash”. Please get a second opinion from another mechanic. His comment makes him sound a little shady in my opinion.

I made a mistake. I found the information sheet the mechanic gave to me; it’s basically a diagram of an engine that he gave to me to explain what’s going on with the car. Anyway, he wrote that the the compression in 2 and 3 is 120, not 140. Didn’t know if that makes a difference.

I am going to get my second opinion tomorrow. i found a shop that specializes i engine issues.

A 140 is abnormally low and 120 is even worse. When you have an in-line 4 cylinder engine and 2 adjacent cylinders have lower than normal compression this generally means a leaking head gasket. This is especially true if it’s the 2 center cylinders that are involved.

Replacing the head gasket is normally not opening up a can of worms unless there are a few extenuating circumstances to go along with it. That would be loss of coolant, overheating, or abnormally low compression readings on the 2 outer cylinders.
Did he happen to mention what the numbers are on those 2 outers?

Cylinder 1 and 4 are at 160 psi.

Actually, 160 is a bit low and this could be attributed to more wear than usual, oil coking, or any past overheating episodes.

What should have been done during the compression test (I’m assuming it was not) is that the original test should have been followed up with what is called a wet test.
This simply means the compression is retested with each cylinder getting a small squirt of motor oil before the test. If the readings take a jump upwards (say from 120 to 150, 160 to 180, etc) then the piston rings are worn. This is major of course and would mean a re-ring job at the least and an overhaul at worst.

I have a feeling that if the compression is retested you are going to find a ring problem. It could also be that the engine has severely overheated in the past and the center 2 cylinders compression being low could be due to fried piston rings. The center 2 cylinders will also be the ones that have a tendency to run hotter than the outer 2.

At this point I would say hold off on any head gasket fix until the ring condition situation is cleared up and I might ask if you bought this car new or used?

If the rest of the car is in decent shape replacing the engine would make more sense than replacing the whole car.

I wasn’t that concerned with 140, I’ve seen reasonably good engines run at that pressure. 120 does concern me, especially with the other two at 160. I fully concur with everything else that OK4450 said.

Got the second opinion today, it’s not the gasket! It’s an issue with the head and the engine has to come out! He conducted more test, said that when he puts air into cylinder 2 and 3, it goes into 1 and 4( I hope I am recalling this correctly.). Said he is certain the problem is with the valves but he has to take the engine out , take it apart to make sure. Worse case scenario, engine replacement.

Ok Air into 2 & 3 comes out 1 & 4 Thats a bad head gasket or cracked head. If the oil presser is ok. I cant see why he would pull the engine. I would pull the head first. Look things over,before I would pull the engine.

I might be wrong but to me seems like the more practical solution is a newer/used engine from a salvage yard with some warranty.

I’m not sure this is being related correctly. The engine does not have to be removed to perform cylinder head work and it’s extremely unclear how this air test was done.

If the air going into 2&3 comes out 1&4, then all cylinders would have low compression. Find another mechanic for a third opinion.