How long does a compression and leakdown test take?
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From: Montreal
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How long does a compression and leakdown test take?
Hey guys,
Have a purchase of sale agreement for a 996tt in Montreal. Looking for a garage to do my PPI with. Visited two garages today, both are highly recommended, both owners spent time with me showing me their current projects etc. One shop is more of a "street car" repair shop (high end generalist: Had 3 porsches on his lift, a DB9, a Merc and had just finished a Rolls Royce Turbo engine rebuild) and the other is more of a "track/mod" repair shop (had 2 997 GT RS'es, Cayman S, 986 Targa, and a honda civic in his shop).
I want to run a leakdown and compression test on the car. The generalist said it would take about 4 hours and wanted to do it when the engine was cold.
The track guy said it would take 1.5 hours. He had the 997 GT RS on the lift and showed me exactly what he has to do and said that it takes 4 hours to do a compression and leakdown for someone who hasn't done one before. He also said he would ideally do it when the engine is cold and also when the engine is up to temp.
When I told the generalist that the track guy said 1.5 hours, he was pretty surprised and said that it was impossible.
Both guys seem like straight arrows, honest and reputable. So how long does one of these tests take and any thoughts on who I should go with?
Have a purchase of sale agreement for a 996tt in Montreal. Looking for a garage to do my PPI with. Visited two garages today, both are highly recommended, both owners spent time with me showing me their current projects etc. One shop is more of a "street car" repair shop (high end generalist: Had 3 porsches on his lift, a DB9, a Merc and had just finished a Rolls Royce Turbo engine rebuild) and the other is more of a "track/mod" repair shop (had 2 997 GT RS'es, Cayman S, 986 Targa, and a honda civic in his shop).
I want to run a leakdown and compression test on the car. The generalist said it would take about 4 hours and wanted to do it when the engine was cold.
The track guy said it would take 1.5 hours. He had the 997 GT RS on the lift and showed me exactly what he has to do and said that it takes 4 hours to do a compression and leakdown for someone who hasn't done one before. He also said he would ideally do it when the engine is cold and also when the engine is up to temp.
When I told the generalist that the track guy said 1.5 hours, he was pretty surprised and said that it was impossible.
Both guys seem like straight arrows, honest and reputable. So how long does one of these tests take and any thoughts on who I should go with?
I believe it would take closer to 4 hours,,just look how long it takes to do a plug swap and then add the time for the test..
I do my leak down tests on my other vehicles with the motor warm..
Maybe the cranking compression test will show good results and the plugs will show no sign of oil residue..
Good Luck..
I do my leak down tests on my other vehicles with the motor warm..
Maybe the cranking compression test will show good results and the plugs will show no sign of oil residue..
Good Luck..
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Joined: Jun 2009
Posts: 2,190
From: Benton County, AR
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Hey guys,
Have a purchase of sale agreement for a 996tt in Montreal. Looking for a garage to do my PPI with. Visited two garages today, both are highly recommended, both owners spent time with me showing me their current projects etc. One shop is more of a "street car" repair shop (high end generalist: Had 3 porsches on his lift, a DB9, a Merc and had just finished a Rolls Royce Turbo engine rebuild) and the other is more of a "track/mod" repair shop (had 2 997 GT RS'es, Cayman S, 986 Targa, and a honda civic in his shop).
I want to run a leakdown and compression test on the car. The generalist said it would take about 4 hours and wanted to do it when the engine was cold.
The track guy said it would take 1.5 hours. He had the 997 GT RS on the lift and showed me exactly what he has to do and said that it takes 4 hours to do a compression and leakdown for someone who hasn't done one before. He also said he would ideally do it when the engine is cold and also when the engine is up to temp.
When I told the generalist that the track guy said 1.5 hours, he was pretty surprised and said that it was impossible.
Both guys seem like straight arrows, honest and reputable. So how long does one of these tests take and any thoughts on who I should go with?
Have a purchase of sale agreement for a 996tt in Montreal. Looking for a garage to do my PPI with. Visited two garages today, both are highly recommended, both owners spent time with me showing me their current projects etc. One shop is more of a "street car" repair shop (high end generalist: Had 3 porsches on his lift, a DB9, a Merc and had just finished a Rolls Royce Turbo engine rebuild) and the other is more of a "track/mod" repair shop (had 2 997 GT RS'es, Cayman S, 986 Targa, and a honda civic in his shop).
I want to run a leakdown and compression test on the car. The generalist said it would take about 4 hours and wanted to do it when the engine was cold.
The track guy said it would take 1.5 hours. He had the 997 GT RS on the lift and showed me exactly what he has to do and said that it takes 4 hours to do a compression and leakdown for someone who hasn't done one before. He also said he would ideally do it when the engine is cold and also when the engine is up to temp.
When I told the generalist that the track guy said 1.5 hours, he was pretty surprised and said that it was impossible.
Both guys seem like straight arrows, honest and reputable. So how long does one of these tests take and any thoughts on who I should go with?
Visit the car cold and with the A/C off verify the warning lights all come on -- especially the CEL! -- and all go off when the engine starts.
Let the engine idle until warm. All the time listen to the engine as it transitions from cold, to warm to nearly hot.
After 10 or more minutes of idling then have the seller take you on a test ride. He should drive a 15 mile route that gives him the opportunity to demo the car in a variety of situations.
Back at the starting point you drive the car over the route and drive the car the same way.
A compression or leak down test does not even tell you if the engine runs, let alone if it misfires or overheats or leaks, or has other issues.
A compression test done cold can deliver erroneous results. The 1st cylinder is "dry" and clearances are large and thus delivers a low compression number.
Subsequent cylinders now wet with oil from the oil jets deliver better numbers as the testing progresses from the 1st to the last cylinder.
Testing the engine warm is not without its own risks. As testing progresses the engine cools and the numbers change from what they would be were all cylinders tested with the engine temp constant.
(Another issue I have with any test that involves removing the spark plugs is the plugs should not be reused. OE plugs come with a dry thread lube that is a one shot deal. The idea is when the plug is removed it is replaced. Reinstalling a plug previously removed runs the risk of spark plug thread damage from the plug and head threads galling due to the now depleted dry thread lube or plug seizure in the head.)
After the test ride and drive then with the engine having run a good hour and the car having been used for about that long then a PPI is done. If there are any fluid leaks they have a much better chance of being spotted from the engine/car having been used before.
A compression test is nearly useless unless the engine is sick so sick a test ride/drive described above would have you back home in time for cornflakes rather than spending any more time with a car with an obviously sick engine.
And a leak down test? This is best reserved for trying to determine why an engine is sick. In your case unless you are buying a project car with a sick engine to resurrect forget this test.
Registered User
Joined: Mar 2008
Posts: 2,807
From: Montreal Canada
Rep Power: 268
Hey guys,
Have a purchase of sale agreement for a 996tt in Montreal. Looking for a garage to do my PPI with. Visited two garages today, both are highly recommended, both owners spent time with me showing me their current projects etc. One shop is more of a "street car" repair shop (high end generalist: Had 3 porsches on his lift, a DB9, a Merc and had just finished a Rolls Royce Turbo engine rebuild) and the other is more of a "track/mod" repair shop (had 2 997 GT RS'es, Cayman S, 986 Targa, and a honda civic in his shop).
I want to run a leakdown and compression test on the car. The generalist said it would take about 4 hours and wanted to do it when the engine was cold.
The track guy said it would take 1.5 hours. He had the 997 GT RS on the lift and showed me exactly what he has to do and said that it takes 4 hours to do a compression and leakdown for someone who hasn't done one before. He also said he would ideally do it when the engine is cold and also when the engine is up to temp.
When I told the generalist that the track guy said 1.5 hours, he was pretty surprised and said that it was impossible.
Both guys seem like straight arrows, honest and reputable. So how long does one of these tests take and any thoughts on who I should go with?
Have a purchase of sale agreement for a 996tt in Montreal. Looking for a garage to do my PPI with. Visited two garages today, both are highly recommended, both owners spent time with me showing me their current projects etc. One shop is more of a "street car" repair shop (high end generalist: Had 3 porsches on his lift, a DB9, a Merc and had just finished a Rolls Royce Turbo engine rebuild) and the other is more of a "track/mod" repair shop (had 2 997 GT RS'es, Cayman S, 986 Targa, and a honda civic in his shop).
I want to run a leakdown and compression test on the car. The generalist said it would take about 4 hours and wanted to do it when the engine was cold.
The track guy said it would take 1.5 hours. He had the 997 GT RS on the lift and showed me exactly what he has to do and said that it takes 4 hours to do a compression and leakdown for someone who hasn't done one before. He also said he would ideally do it when the engine is cold and also when the engine is up to temp.
When I told the generalist that the track guy said 1.5 hours, he was pretty surprised and said that it was impossible.
Both guys seem like straight arrows, honest and reputable. So how long does one of these tests take and any thoughts on who I should go with?
It is simply impossible to do a leakdown test in one hour. This guy don't know what he's talking about or never work on a turbo before. It can be done in 3 to 4 hours minimum. What shop you went to? Are you looking at the red GT2 that's on the market? If so be aware there are problems with this car.
Last edited by jpflip; Mar 29, 2013 at 04:13 PM.
About an hour or so.
Visit the car cold and with the A/C off verify the warning lights all come on -- especially the CEL! -- and all go off when the engine starts.
Let the engine idle until warm. All the time listen to the engine as it transitions from cold, to warm to nearly hot.
After 10 or more minutes of idling then have the seller take you on a test ride. He should drive a 15 mile route that gives him the opportunity to demo the car in a variety of situations.
Back at the starting point you drive the car over the route and drive the car the same way.
A compression or leak down test does not even tell you if the engine runs, let alone if it misfires or overheats or leaks, or has other issues.
A compression test done cold can deliver erroneous results. The 1st cylinder is "dry" and clearances are large and thus delivers a low compression number.
Subsequent cylinders now wet with oil from the oil jets deliver better numbers as the testing progresses from the 1st to the last cylinder.
Testing the engine warm is not without its own risks. As testing progresses the engine cools and the numbers change from what they would be were all cylinders tested with the engine temp constant.
(Another issue I have with any test that involves removing the spark plugs is the plugs should not be reused. OE plugs come with a dry thread lube that is a one shot deal. The idea is when the plug is removed it is replaced. Reinstalling a plug previously removed runs the risk of spark plug thread damage from the plug and head threads galling due to the now depleted dry thread lube or plug seizure in the head.)
After the test ride and drive then with the engine having run a good hour and the car having been used for about that long then a PPI is done. If there are any fluid leaks they have a much better chance of being spotted from the engine/car having been used before.
A compression test is nearly useless unless the engine is sick so sick a test ride/drive described above would have you back home in time for cornflakes rather than spending any more time with a car with an obviously sick engine.
And a leak down test? This is best reserved for trying to determine why an engine is sick. In your case unless you are buying a project car with a sick engine to resurrect forget this test.
Visit the car cold and with the A/C off verify the warning lights all come on -- especially the CEL! -- and all go off when the engine starts.
Let the engine idle until warm. All the time listen to the engine as it transitions from cold, to warm to nearly hot.
After 10 or more minutes of idling then have the seller take you on a test ride. He should drive a 15 mile route that gives him the opportunity to demo the car in a variety of situations.
Back at the starting point you drive the car over the route and drive the car the same way.
A compression or leak down test does not even tell you if the engine runs, let alone if it misfires or overheats or leaks, or has other issues.
A compression test done cold can deliver erroneous results. The 1st cylinder is "dry" and clearances are large and thus delivers a low compression number.
Subsequent cylinders now wet with oil from the oil jets deliver better numbers as the testing progresses from the 1st to the last cylinder.
Testing the engine warm is not without its own risks. As testing progresses the engine cools and the numbers change from what they would be were all cylinders tested with the engine temp constant.
(Another issue I have with any test that involves removing the spark plugs is the plugs should not be reused. OE plugs come with a dry thread lube that is a one shot deal. The idea is when the plug is removed it is replaced. Reinstalling a plug previously removed runs the risk of spark plug thread damage from the plug and head threads galling due to the now depleted dry thread lube or plug seizure in the head.)
After the test ride and drive then with the engine having run a good hour and the car having been used for about that long then a PPI is done. If there are any fluid leaks they have a much better chance of being spotted from the engine/car having been used before.
A compression test is nearly useless unless the engine is sick so sick a test ride/drive described above would have you back home in time for cornflakes rather than spending any more time with a car with an obviously sick engine.
And a leak down test? This is best reserved for trying to determine why an engine is sick. In your case unless you are buying a project car with a sick engine to resurrect forget this test.
It as a Basic 101 start to most mechanical engine testing..
The compression test readings will show you if the motor is some what sound by comparing the numbers,strength,of each cylinder for uniformity..If one is way lower then the highest average,,then you should proceed to a leak down in that cylinder that is low to check condition of rings seal,valve seal and if done right the bore condition also.
A basic leak down will take a while because you have to bring each cylinder you test up to TDC firing,,,all valves closed in that test cylinder...That will determine where and how much/bad the leak is..
I hope this helps..Good Luck..
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