Compression problems ...!!! Help wanted ..

[celica2004]

HI,

I brought a 1993 toyota corolla (143 K) yest. for $1500 . When got a maintenance report from a service centre they said that the compression ratios in the engines are #1) 130 , #2) 110 , #3) 30 , #4) 130.. and also said that it may give some big probs in near future...


How good is their judgement dudes..?? They also recommended me to change VC Gasket (Leak).. Will it help if I change the gasket ($30 ) ??

I appreceiate your answers..


thanks.
New Corollate..

[Toysrme]

142 psi minimun and 178 psi normal.
Anything between the two is OK as long as everything is fairly consistant.

If the valve cover gasket is leaking change it. I know my v6 gaskets are $12 online, and from stores in-person. I would think they're overcharging you for the gasket by mroe than double, considering they have absolutely 0 extra work to change it.


You obviously got a problem.

[cobrajet25]

Your shop was not talking about compression RATIOS, but rather the actual compression PRESSURES inside the cylinders. Big difference. Compression ratio is the difference in the volume of the cylinder while the piston is at the bottom of it's travel versus the volume while it is at the top of it's travel. It is expressed as a ratio, like 8.5-to-1 or 9.3-to-1 or something. If your engine has an 8.5-1 compression ratio, then there is 8.5 times more space in the cylinder when the piston is at the bottom of the cylinder than when it is at the top. Wear does not affect the compression ratio too much.

Compression pressure is the actual pressure (expressed in Pounds per Square Inch, or PSI) of the air/fuel mixture that each cylinder builds up when the piston goes from the bottom of the cylinder to the top on the compression stroke. Compression pressure (or just "compression", as it is commonly called among gearheads) is greatly affected by wear. As cylinder walls, rings, and valves wear out (due to lack of maintenance or high mileage), they are no longer able to keep as much pressure in the cylinder when the piston reaches the top of the cylinder. The compressed air/fuel mixture leaks past worn valves and rings, so there is less air/fuel mixture in the cylinder for combustion when the spark plug fires. This obviously leads to less power, and a condition called "blow-by".

If you are only running 30 psi on #3, then that cylinder is for all purposes dead. Essentially, you have a 3 cylinder car. Since the other cylinders are all low but fairly even, I doubt that it is a blown head gasket. Normally a blown head gasket will show up as two really low cylinders that are next to each other, but sometimes it only affects one cylinder. A good sign of a blown head gasket is coolant in your oil or oil in your coolant, which your mechanic would have surely spotted. Chances are it is a burnt valve, a bent valve, or a broken compression ring (or two) on the number three cylinder. Since the other three cylinders are all well below the minimum recommended compression (142 psi, as Toysrme said), the engine is just plain worn out and needs to be either rebuilt or replaced. Bummer. Changing the valve cover gasket wouldn't help a bit unless you are trying to stop an oil leak. That engine is gone.... You can get a 4A-FE crate motor with 30-40k on it for $300-$400 with a little searching, and if you change the motor youself you would have a great car for under $2000. Even if you paid to have the motor changed, you would still only be in it for about $2500..not bad for a car that now only has 30,000 miles on it! These engines are pretty easy to find at wrecking yards, too, and prices are cheaper. If these cars are maintained they can easily reach 300,000 miles and still run great. The 4A-FE is an extremely well-built and well-designed motor...one of Toyota's best. If they are not, then 100-125,000 is about all they are good for (which is still more than most cars are capable of). Good luck. Regards, Aaron

[celica2004]

Originally Posted by cobrajet25

Your shop was not talking about compression RATIOS, but rather the actual compression PRESSURES inside the cylinders. Big difference. Compression ratio is the difference in the volume of the cylinder while the piston is at the bottom of it's travel versus the volume while it is at the top of it's travel. It is expressed as a ratio, like 8.5-to-1 or 9.3-to-1 or something. If your engine has an 8.5-1 compression ratio, then there is 8.5 times more space in the cylinder when the piston is at the bottom of the cylinder than when it is at the top. Wear does not affect the compression ratio too much.

Compression pressure is the actual pressure (expressed in Pounds per Square Inch, or PSI) of the air/fuel mixture that each cylinder builds up when the piston goes from the bottom of the cylinder to the top on the compression stroke. Compression pressure (or just "compression", as it is commonly called among gearheads) is greatly affected by wear. As cylinder walls, rings, and valves wear out (due to lack of maintenance or high mileage), they are no longer able to keep as much pressure in the cylinder when the piston reaches the top of the cylinder. The compressed air/fuel mixture leaks past worn valves and rings, so there is less air/fuel mixture in the cylinder for combustion when the spark plug fires. This obviously leads to less power, and a condition called "blow-by".

If you are only running 30 psi on #3, then that cylinder is for all purposes dead. Essentially, you have a 3 cylinder car. Since the other cylinders are all low but fairly even, I doubt that it is a blown head gasket. Normally a blown head gasket will show up as two really low cylinders that are next to each other, but sometimes it only affects one cylinder. A good sign of a blown head gasket is coolant in your oil or oil in your coolant, which your mechanic would have surely spotted. Chances are it is a burnt valve, a bent valve, or a broken compression ring (or two) on the number three cylinder. Since the other three cylinders are all well below the minimum recommended compression (142 psi, as Toysrme said), the engine is just plain worn out and needs to be either rebuilt or replaced. Bummer. Changing the valve cover gasket wouldn't help a bit unless you are trying to stop an oil leak. That engine is gone.... You can get a 4A-FE crate motor with 30-40k on it for $300-$400 with a little searching, and if you change the motor youself you would have a great car for under $2000. Even if you paid to have the motor changed, you would still only be in it for about $2500..not bad for a car that now only has 30,000 miles on it! These engines are pretty easy to find at wrecking yards, too, and prices are cheaper. If these cars are maintained they can easily reach 300,000 miles and still run great. The 4A-FE is an extremely well-built and well-designed motor...one of Toyota's best. If they are not, then 100-125,000 is about all they are good for (which is still more than most cars are capable of). Good luck. Regards, Aaron

Thanks Aaron ,,


Thanks for your valuable reply.. My mechanic suggested me to repair
1) Cooling system flush
2) fuel injection cleaning
3) distributor cap
4) rotor button
5) ignition wires
6) Oxygen sensor
7) VC Gasket (LEAK)
8)Brake fluid/flush
9) Struts/shocks



Please suggest me which one is more important for time being.. and which will help to solve the problem associated with low compression..

Can we guss what went wrong with my engine using the above information.???

Appreciate your answer...

Thanks,

James.

[Raddman]

Originally Posted by celica2004

Thanks Aaron ,,


Thanks for your valuable reply.. My mechanic suggested me to repair
1) Cooling system flush
2) fuel injection cleaning
3) distributor cap
4) rotor button
5) ignition wires
6) Oxygen sensor
7) VC Gasket (LEAK)
8)Brake fluid/flush
9) Struts/shocks



Please suggest me which one is more important for time being.. and which will help to solve the problem associated with low compression..

Can we guss what went wrong with my engine using the above information.???

Appreciate your answer...

Thanks,

James.

None!!! Get another mechanic because this one is trying to rip you off big time, none of those things he suggested will help/solve your "compression problem" Did you read Aarons complete post and did anything sink in? As Aaron suggested you need a complete engine rebuild or a rebuilt/used engine...I'm not trying to be a smart A$$ but apperantly you know nothing about cars and I hate to see people like you get ripped off by shady machanics... At lease get another opinion before you start sinking money into your car for things you don't need and won't solve your original problem....JMHO ...Raddman
__________________________________________________ _________________________________

"HONK IF YOU HATE NOISE"

[TekPhobia]

So..how does the car run? Does it lack power? Rough idle?

It would be good to find a GOOD mechanic to do a compression test (wet) and a leakdown to see WHERE the problem is.

-Tim

[celica2004]

thanks Tim

The car runs fine... But Aaron said that my car will not have full power.. i tried to drive at 75 Mph .. it was fine.. can u tell me how much leakdown test costs.. ?? and what may be the potential problems in that??

apprecieate ur answer.

[TekPhobia]

Well, I only question the original compression test results. A cylinder with 30psi would be very noticeable (i.e., rough idle, etc.).

I honestly don't know how much a leakdown test would cost. I figure an hour of a mechanics time should be enough. If in fact the HG/rings are shot, the leakdown will help determine that.

-Tim

[reym]

TekPhopia is right, A cylinder with 30 psi means the engine would run rough and hard to accelerate from 0. You would feel some drag as you accelerate from 0. The performace becomes terriblly noticable when climbing uphill. Kindly check your battery because compression depends on crank rpm. Try another mechanic.

[cobrajet25]

I agree with everyone here. If your car seems to run alright, the compression figures provided by your mechanic are probably wrong. A cylinder only running 30 psi would create some real issues, particularly at idle. As I said, that cylinder is not really contributing much. Go to another mechanic and have another compression test done, as he may get different numbers. That is the best advice I can give you. While it might be interesting to do a leakdown test and find out what the exact problem is, it would just be an academic exercise. If the compression is actually that low, then a rebuild or replacement is in order whether the problem is the valves OR the rings. Not worth doing a leakdown test, and I instead would spend the money making sure the compression figures are correct by going somewhere else.

If the car runs and idles okay now, then you might just drive it until the engine gives up completely. I personally would not put any money into that engine if the compression is actually that low. Doing what your mechanic is suggesting will accomplish nothing but lining his pockets, and if his compression figures are right he DAMN WELL KNOWS IT. There is NO point in replacing external parts on an engine with that kind of internal wear. Sounds like that guy is just a pirate. Have your compression figures double-checked by another mechanic, or you can even do-it-yourself. Compression testers are available at any parts store for about $30. All you have to do is take out all of the spark plugs, disconnect the coil wire, block the throttle wide open, screw the tester tightly into a spark plug hole, and crank the engine over for about 5-10 seconds. The reading on the tester is your compression. Repeat this for all four cylinders. Good luck, and keep us posted. Regards, Aaron

[celica2004]

thanks Aaron,

I will get a compression tester and test it by myself.. And will post my updates..

thanks for ur advice..

[celica2004]

Originally Posted by cobrajet25

Your shop was not talking about compression RATIOS, but rather the actual compression PRESSURES inside the cylinders. Big difference. Compression ratio is the difference in the volume of the cylinder while the piston is at the bottom of it's travel versus the volume while it is at the top of it's travel. It is expressed as a ratio, like 8.5-to-1 or 9.3-to-1 or something. If your engine has an 8.5-1 compression ratio, then there is 8.5 times more space in the cylinder when the piston is at the bottom of the cylinder than when it is at the top. Wear does not affect the compression ratio too much.

Compression pressure is the actual pressure (expressed in Pounds per Square Inch, or PSI) of the air/fuel mixture that each cylinder builds up when the piston goes from the bottom of the cylinder to the top on the compression stroke. Compression pressure (or just "compression", as it is commonly called among gearheads) is greatly affected by wear. As cylinder walls, rings, and valves wear out (due to lack of maintenance or high mileage), they are no longer able to keep as much pressure in the cylinder when the piston reaches the top of the cylinder. The compressed air/fuel mixture leaks past worn valves and rings, so there is less air/fuel mixture in the cylinder for combustion when the spark plug fires. This obviously leads to less power, and a condition called "blow-by".

If you are only running 30 psi on #3, then that cylinder is for all purposes dead. Essentially, you have a 3 cylinder car. Since the other cylinders are all low but fairly even, I doubt that it is a blown head gasket. Normally a blown head gasket will show up as two really low cylinders that are next to each other, but sometimes it only affects one cylinder. A good sign of a blown head gasket is coolant in your oil or oil in your coolant, which your mechanic would have surely spotted. Chances are it is a burnt valve, a bent valve, or a broken compression ring (or two) on the number three cylinder. Since the other three cylinders are all well below the minimum recommended compression (142 psi, as Toysrme said), the engine is just plain worn out and needs to be either rebuilt or replaced. Bummer. Changing the valve cover gasket wouldn't help a bit unless you are trying to stop an oil leak. That engine is gone.... You can get a 4A-FE crate motor with 30-40k on it for $300-$400 with a little searching, and if you change the motor youself you would have a great car for under $2000. Even if you paid to have the motor changed, you would still only be in it for about $2500..not bad for a car that now only has 30,000 miles on it! These engines are pretty easy to find at wrecking yards, too, and prices are cheaper. If these cars are maintained they can easily reach 300,000 miles and still run great. The 4A-FE is an extremely well-built and well-designed motor...one of Toyota's best. If they are not, then 100-125,000 is about all they are good for (which is still more than most cars are capable of). Good luck. Regards, Aaron

HI Aaron,

I tested the compression in the cylinders of the engine in my car. I found that they are 1)180,2)185,3)181,4)180.

Once I took it to a mechanic he said that the compressions which are far away from the readings that I got.

The procedure that We followed in doing this is
1) Ran the car for a while
2) Stopped the engine, and removed spark plug wires in all the cylinders, and removed spark plug of each cylinder at a time,
3) Inserted the compression tester into the cylinder, and cranked the engine ( obvisiouly engine will not start).
4) and noted the reading on the compression tester.

Is this procedure a right way to conduct it.. are my readings reliable.??

Hope to hear from u soon.

Thanks,
new corollate

[toyotaspeed90]

ok first off..... if you have compression that low in one cylinder it's generally a HEADGASKET..... in all of the ramblings above nobody even mentioned that ..... but worst case scenario would be a piston ring (and by no means actually requires a full rebuild)

in any case.... the route you went to test it yourself seems to be accurate...... doesn't really matter if the engine was running previously or not (essentialy you did a "wet test" without actually adding oil to the system...... a wet test can help see if you have a loss of compression through the rings)