So I'm diagnosing some problems with my engine, and figured I'd pick up a cheap compression and leakdown tester from Amazon. When I get this stuff in the mail, it comes in a nice handy box, but I found a piece of old machined burs stuck inside one of the fittings:
I would have been a very unhappy camper if that had fallen into my cylinder. Also, the fittings used to screw into the spark plug well are too wide. I think this is probably common for several testing kits out there, so I had to buy a Lisle 12mm adapter. While I was at it, I bought a remote starter trigger switch, this made the compression test and finding TDC for the leakdown a breeze.
I decided to take a crack at this with a cold engine. Due to various circumstances, it was just too much of a pain to keep the engine warm for all of this testing while considering I'm doing only a little at a time. The temps in my garage are akin to a convection oven when the 110* ambient temps outside are accounted for, so stints working on the car are fairly brief as I'm quickly drenched in sweat, despite a portable swamp cooler being present and waiting until the evening.
The first tests showed about 155 psi in pretty much all cylinders, with cylinder 3 having a one time spike up to 165.
This didn't make a lot of sense to me, my last compression reading done by a BMW technician was "175 across the board" according to him. But when the cold engine is put into the equation, I suppose it is possible but I didn't hold much confidence in these results. They all matched up so well, it just screamed there was a leak in my testing equipment at that pressure.
I moved onto my leakdown test, put 90 PSI in my tank and hooked up the tester. It turns out, that when you calibrate the testing gauge to 0 leakage before starting, it only accepts approximately 31-32 psi of pressure into the system. So instead of the leakdown test being performed at 90+ psi, they were done at a third of that.
As expected, results were eerily similar, less than 5% on all cylinders:
So while the leakdown results were good and the compression results were meh, I decided these mediocre/garbage results were likely due to mediocre/garbage testing tools. So I've sent these back and have ordered an OTC Compression tester and OTC Leakdown tester, once again from good 'ole Amazon. The price for the China special compression and leakdown tester totalled $56.40, while the OTC pair came to $117.37. So the OTC stuff was $60 more and also requires the Lisle 12mm fitting... But was it worth it?
Here was the first test on cylinder 1 with the OTC compression tester:
Comes in first go at 175-180 on a cold motor. It is late and did not have time to finish testing but I wanted to come in here and point out the obvious, don't use that cheap crap for anything larger than a Briggs and Stratton lawn mower engine, and that is being generous. I'll update the thread later with my full compression and leakdown results for posterity.
UPDATE:
Here are the other five cylinder compression results:
So you can see that Cylinder 6 is a bit low once again. About 157 PSI vs 170 for the rest. Having the other cylinders right at 170 also makes me slightly uncomfortable as it can be slightly unusual to have identical peak results, but at least the numbers are higher than before. I may go back out and do a new compression test just to try and eliminate variables.
1: 175
2: 170
3: 170
4: 170
5: 170
6: 157
So for good measure I went out and did another compression test:
1: 179
2: 170
3: 173
4: 174
5: 173
6: 168
So this looks much better, at least the integrity of the results. There is an 11 PSI swing between Cylinder 1 and 6 however.
I would have been a very unhappy camper if that had fallen into my cylinder. Also, the fittings used to screw into the spark plug well are too wide. I think this is probably common for several testing kits out there, so I had to buy a Lisle 12mm adapter. While I was at it, I bought a remote starter trigger switch, this made the compression test and finding TDC for the leakdown a breeze.
I decided to take a crack at this with a cold engine. Due to various circumstances, it was just too much of a pain to keep the engine warm for all of this testing while considering I'm doing only a little at a time. The temps in my garage are akin to a convection oven when the 110* ambient temps outside are accounted for, so stints working on the car are fairly brief as I'm quickly drenched in sweat, despite a portable swamp cooler being present and waiting until the evening.
The first tests showed about 155 psi in pretty much all cylinders, with cylinder 3 having a one time spike up to 165.
This didn't make a lot of sense to me, my last compression reading done by a BMW technician was "175 across the board" according to him. But when the cold engine is put into the equation, I suppose it is possible but I didn't hold much confidence in these results. They all matched up so well, it just screamed there was a leak in my testing equipment at that pressure.
I moved onto my leakdown test, put 90 PSI in my tank and hooked up the tester. It turns out, that when you calibrate the testing gauge to 0 leakage before starting, it only accepts approximately 31-32 psi of pressure into the system. So instead of the leakdown test being performed at 90+ psi, they were done at a third of that.
As expected, results were eerily similar, less than 5% on all cylinders:
So while the leakdown results were good and the compression results were meh, I decided these mediocre/garbage results were likely due to mediocre/garbage testing tools. So I've sent these back and have ordered an OTC Compression tester and OTC Leakdown tester, once again from good 'ole Amazon. The price for the China special compression and leakdown tester totalled $56.40, while the OTC pair came to $117.37. So the OTC stuff was $60 more and also requires the Lisle 12mm fitting... But was it worth it?
Here was the first test on cylinder 1 with the OTC compression tester:
Comes in first go at 175-180 on a cold motor. It is late and did not have time to finish testing but I wanted to come in here and point out the obvious, don't use that cheap crap for anything larger than a Briggs and Stratton lawn mower engine, and that is being generous. I'll update the thread later with my full compression and leakdown results for posterity.
UPDATE:
Here are the other five cylinder compression results:
So you can see that Cylinder 6 is a bit low once again. About 157 PSI vs 170 for the rest. Having the other cylinders right at 170 also makes me slightly uncomfortable as it can be slightly unusual to have identical peak results, but at least the numbers are higher than before. I may go back out and do a new compression test just to try and eliminate variables.
1: 175
2: 170
3: 170
4: 170
5: 170
6: 157
So for good measure I went out and did another compression test:
1: 179
2: 170
3: 173
4: 174
5: 173
6: 168
So this looks much better, at least the integrity of the results. There is an 11 PSI swing between Cylinder 1 and 6 however.
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