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How do I get compression into my engine? Answered

I have a 2000 Grand Am Pontiac 6 cylinder. I have low to no compression in my engine, i haven't got a compression test done, at first I thought it was because I had a hole in my radiator hose, but i changed that along with my battery and both are perfectly fine, but car still won't start. It makes the sound like there is no compression, so I was wondering how do you get compression back into an engine. I spoke with a mechanic and he said that i could pour transmission oil into the spark plugs and that should do, I just wanted a second oppinon and see if there are any other ideas.


Well compression is very essential to diagnose engine problems and increase your engine performance as well. After a certain time, every engine has the same problem especially in 4 cylindrical. It is rare in 6 cylindrical engine as available at buyusedengine.com/ but if it occurs then you need to do the following:

Borrow or buy a diagnostic vacuum gauge it will help a lot. Hook the engine to intake manifold-port directly and just start the engine. Let the engine to warm up for a time and be stabilized. Not the reading carefully, it should not above 20" at warm idle. Do it with each of your cylinder one by one.

I have Chevrolet 235 full pressure 6 cylinder motor 1953 and am having the same issue since long.....

I have checked timing belt as Jonorth said but its fine, is there any other issue that haven't noticed yet...??

Have you checked your timing belt or chain to see if its broken ?

You seem sure that you have no compression, but really-vague about what the problem is.

You could ask a mechanic to diagnose it.
You could take the engine apart so far as to remove the cylinder-head(s) and show us photos.

I.e. either start on it with some tools or pay someone else to look at it first.


Pouring transmission oil into the spark plugs is a wrong-idea for a compression problem. Also, the radiator-hose and the battery do not affect compression.

According to the How Stuff Works site, these might be the cause for no compression:

Lack of compression - If the charge of air and fuel cannot be compressed properly, the combustion process will not work like it should. Lack of compression might occur for these reasons:

  • Your piston rings are worn (allowing air/fuel to leak past the piston during compression).
  • The intake or exhaust valves are not sealing properly, again allowing a leak during compression.
  • There is a hole in the cylinder.

The most common "hole" in a cylinder occurs where the top of the cylinder (holding the valves and spark plug and also known as the cylinder head) attaches to the cylinder itself. Generally, the cylinder and the cylinder head bolt together with a thin gasket pressed between them to ensure a good seal. If the gasket breaks down, small holes develop between the cylinder and the cylinder head, and these holes cause leaks.

My advice is, take your car to a real mechanic. This is a problem that you are not going to be able to fix on your own.

You might want to buy the compression guage and check EACH cylinder. Then you will know how much compression each cylinder has. It might be that all cylinders have low compression which might indicate lots of engine wear. Or you might have 1 or 2 pistons that have the problem but the others are OK? By doing this test, you will learn a little about the problem and be better able to make your decision about what to do. From the way you ask the question, I suspect you REALLY DONT KNOW what is wrong but you are guessing it has low compression. If this is the case, your question should have been "why won't my engine start?" In that case, i would say you need to determine if the problem is one of 2 things. NO SPARK to the spark plugs.... or..... NO GAS to the cylinders. Check for spark by removing a plug and LOOKING while you crank the engine... You should see a spark in the plug if the plug is laying on a metal surface. If it passes that test, then try spraying some ENGINE STARTING FLUID into the air intake. If the engine starts for a few seconds, then the engine STOPS... this tells you the car is simply not getting any GAS.
Might be a bad fuelpump or clogged fuel filter or electrical problem in that area.
If the car passes BOTH those tests... ( it is getting spark and it is getting gas) then the problem might be bad timing ( broken timing belt or other serious problem) which is a problem beyond the scope of what i can help you with.


What your mechanic was telling you to do is PART of a compression test, where adding a few DROPS of oil around the rings can help tell you if you've lost compression because of it.

You need to do a compression test, testers aren't expensive. If you've lost it, there is no choice but to drop the head and investigate further. If you''ve never done it, its not THAT hard to do, but I'd get a friend who has done it to help - there are lots of things to watch and remember.


Compression checker is cheap to buy - or get a garage to check it.

IF it is low possible causes:

Leaking head gasket

Worn cylinder bore

Broken piston rings

worn valve

Dirty valve seat

Carbon build up on the valve stem preventing it closing.

Hole in the piston - sounds unusual but i have seen it.

Cracked cylinder bore.


5 years ago

First, a leaky radiator hose has absolutely no affect at all on an engine's compression. I have worked on engines ever since I was old enough to hand my dad a tool and I have never heard of anyone who could tell if the compression was bad by its sound when it won't run.
Secondly, if the compression is so bad the engine won't start, it is highly unlikely any sort of oil additive will help much, if at all.
A simple way to check the compression is to pull the spark plugs and hold your thumb or the palm of your hand tight against the spark plug,hole sealing it. Then have someone crank the engine. You should able to feel the compression stroke as the compressed air pushes against your thumb.
If the compression feels weak in all six cylinders, you likely have a warped or cracked head, a blown head gasket or both.
If the compression feels weak in only one cylinder, you may have a broken ring, a stuck or broken valve, a broken piston or connecting rod.
If the compression feels good and of near the same strength in all six cylinders, then you probably have a problem unrelated to engine compression.


5 years ago

  1. Did you ever run it ?
  2. Even low compression should start and run in place.
  3. I used STP oil treatment to improve compression on an old Chevy.
  4. Over several fuel tanks of running time the STP builds up a strong  varnish on the piston cylinder walls improving the cars compression.
  5. I never heard of detecting compression by the sound.
  6. There are major different kinds of transmission oils
  7. Take care you could blow the head gasket !
  8. Are you sure the ignition is firing ?

My quess is that you have a broken timing belt. Did the lack of compression start suddenly? When the belt breaks, the engine will turn over but the camshaft doesn't turn so there is no compression. Often when the belt breaks and the camshaft stops, some valves are help open and the pistons will hit some of them.