Low Compression!!!!

[TFFC]

Alright I have a 91 tsi fwd with low compression. I have 60 psi across the boardI have pulled the head and replaced the head gasket, no bent valves. Timing is dead on, good battery, good starter. I have tried everything to get this car to have compression. I can't figure it out, Emissions removed except block off egr. any suggestions on why this is????

 

[talon1987]

sounds like bad piston rings ... if everything else checks out

-Pat

 

[bryanwheat]

Sounds like you need some rings my friend. When you pull the head off, it is always a good idea to pour a very light liquid (alcohol) in the cylinders and see how long it stays. Usually a couple of hours is good. If is leaks thru in a matter of minuted, you need some rings, but from what you are saying, it sounds like you just need to pull the head, pull the oil pan, pull the pistons , check ring lands for damage, hone the block, reinstall the pistins with new rings, reinstall the head, put mr oil pan back on, and call it a day.

 

[JamiesTSI]

Did you try a little oil in each cylinder, before you do the compresion check, to see if the compression goes up?

 

[TFFC]

When I pulled the head off, all the rings looked good, and the walls still had their nice cross hatch pattern. When I did a compression test. I get about 60 PSI on all the cylinders. So I think to myself, What are the chances that all 4 cylinders lost the rings at the same time. So I am not to sure the rings are bad. I need to a leak down test nest, just waiting on a air compressor. Any other ideas??

 

[Old Mitsu Tech]

Well, I was going to suggest a wet compression test. If you pour some light oil in your cylinders and crank it and the compression jumps, it's likely rings. If no change, then valves or other leakages. IE head gasket and such or even the timing belt off a tooth.

When you get the head back on, make absolutely positively sure the timing belt is on properly. To the tooth. One tooth will make low compression, 2 will make evern lower compression. 3 will sometimes bend valves.


Something is causing it. I would look at the timing belt issue as it's the most common to get wrong.

Good Luck

 

[diambo4life]

Two words for you. Leakdown test.

 

[JiggahMan]

Well, I was going to suggest a wet compression test. If you pour some light oil in your cylinders and crank it and the compression jumps, it's likely rings. If no change, then valves or other leakages. IE head gasket and such or even the timing belt off a tooth.

When you get the head back on, make absolutely positively sure the timing belt is on properly. To the tooth. One tooth will make low compression, 2 will make evern lower compression. 3 will sometimes bend valves.


Something is causing it. I would look at the timing belt issue as it's the most common to get wrong.

Good Luck

If you end up putting the oil in the cylinders, MAKE SURE IT GOES TO THE RINGS. NOT in the dish of the piston, that will raise compression for obvious reasons.

 

[sherwinz28]

Try a different compression tester. I just bought a new one and it shows different readings then my old one. My old one was saying like 130-140 and this new one is saying 155+ except for my last cylinder which is 30