I have an 1980's B7100 HST-D, D750 AH engine. It is new to me and it's in fairly good condition for it's age. The engine starts up without prolonged cranking but it smokes way more than I believe it should. After it warms up it still smokes but not nearly as much as at start-up. The breather also smokes but very small amount. Otherwise, the tractor operates to my satisfaction.
I know all the "smoke" talk is very subjective, especially on a tractor of this age and with no working hour meter. I would like to reduce most of the smoking if possible and to that end if have performed the following tests:
Compression Test: Cyl #1: (Dry 240#); (Wet 250#), Cyl #2: (Dry 200#); (Wet 200#), Cyl #3: (Dry 220#); (Wet 240#).
Leak Down Test @ 100 PSI: Cyl #1 = 12%, Cyl #2 = 18%, Cyl #3 = 15%. These tests were done with the push rods removed. I hear quite a bit of air escaping from the intake ports, the intake assembly has been removed. The exhaust is much more quiet and the valve cover vent is also very quiet.
Cranking oil pressure = 40 psi with glow plugs removed.
What has me confused is why does it have such low compression but a very acceptable leak down test. I have also tested the gauges used in these tests to make sure my results were accurate. Unless I am not understanding my results (very possible) and with good oil pressure I think I will have the head reconditioned because of the very noticeable air leak at the intake valves.
My findings don't make a lot of sense to me, low compression but good leak down test, and I am hoping someone can shed some light on why my test results seem to conflict with each other and if starting with reconditioning the head makes sense.
Thank you in advance. Larry
I know all the "smoke" talk is very subjective, especially on a tractor of this age and with no working hour meter. I would like to reduce most of the smoking if possible and to that end if have performed the following tests:
Compression Test: Cyl #1: (Dry 240#); (Wet 250#), Cyl #2: (Dry 200#); (Wet 200#), Cyl #3: (Dry 220#); (Wet 240#).
Leak Down Test @ 100 PSI: Cyl #1 = 12%, Cyl #2 = 18%, Cyl #3 = 15%. These tests were done with the push rods removed. I hear quite a bit of air escaping from the intake ports, the intake assembly has been removed. The exhaust is much more quiet and the valve cover vent is also very quiet.
Cranking oil pressure = 40 psi with glow plugs removed.
What has me confused is why does it have such low compression but a very acceptable leak down test. I have also tested the gauges used in these tests to make sure my results were accurate. Unless I am not understanding my results (very possible) and with good oil pressure I think I will have the head reconditioned because of the very noticeable air leak at the intake valves.
My findings don't make a lot of sense to me, low compression but good leak down test, and I am hoping someone can shed some light on why my test results seem to conflict with each other and if starting with reconditioning the head makes sense.
Thank you in advance. Larry
