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  #11  
Old 05-15-2014, 08:48 AM
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In regular testing with the engine warm on a 1fz with high miles I see into 160+ psi. On cold engines I expect 10-15 lbs. One thing most people testing do not seem to take into account is the carbon build up on a piston. This will increase compression ratio(ever wonder where the pinging is coming from pulling a load on older engines).
Are you trying to figure out where the coolant is coming from? Or just trying to see if it is the head gasket? Coolant on a 1FZ can also come from the front timing cover, as well as the oil cooler. Just put some shop air to #5 with the valves closed and see if you get bubbles or air hissing in the radiator. I usually start with low pressure and increase to 80 psi max
In the long run, I have learned to use these test as a guide. but in the end, with the 1fz and its crappy original head gasket design, and carbon build up, pulling the cylinder head is more valuable to see all you need to know on what is up. Takes a few hours, but you will be light years ahead and not guessing
I know you may not know me, but I have had well over a 100 of these 1fz engines apart in the last 15 years.
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  #12  
Old 05-15-2014, 09:49 AM
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Quote:
Originally Posted by Rzeppa View Post
No, not really. Compression tests are not done at engine operating temperatures, they are always done at ambient temperatures, in order for the results to be meaningful for comparison to specifications. Diagnosing a fault is a completely different scenario and as such testing while at operating temperatures is perfectly acceptable. Most of us do compression tests to see whether we're due for a rebuild or how well our rebuild went! Also, the old "put some oil in each cylinder" test is to see if our low compression is due to worn rings or a valve not sealing well.

Totally agreed about the expansion causing different conditions in compression, including exposing a fault that might not be observable at ambient temperature.
oil in a cylinder making compression go up means worn rings, not valves really.

either way i'm not sure i'd freak out over the variance or even the number itself. Sure it might be worn, but the thing you should figure out is why #5 is low. super easy to do like Robbie said and apply shop air while it's at TDC, valves closed. listen for air from intake, exhaust, and PCV. look for bubbles in coolant. you can do this with the bits from a cheap HF leakdown kit. If it has that low a compression the leakdown numbers are gonna suck anyways so figure out where the air is going. Just be careful.. when you put pressure to a cylinder at TDC it can come off of TDC and spin the motor.... which if you have a manual (i know the 80 is an auto) can move the rig, or if you have a wrench on the crank pulley that you used to move the motor, can hit you in the face.
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  #13  
Old 05-15-2014, 10:32 AM
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Rzeppa Rzeppa is offline
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Quote:
Originally Posted by rover67 View Post
oil in a cylinder making compression go up means worn rings, not valves really.
That's what I wrote - that's how you differentiate whether the low compression is from valves or rings
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  #14  
Old 05-15-2014, 10:39 AM
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but if the oil doesn't do anything it could be other things leaking not just valves. other things that come to mind are head gasket or hole in piston. If it were a goal to differentiate if low compression were from valves or rings I'd pressurize the cylinder as was mentioned above. dumping oil in a cylinder might only tell you if rings are worn or not depending on what else is leaking.
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  #15  
Old 05-16-2014, 02:15 PM
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Usually Coolant is not found in the oil on a Head gasket failure of minor degree. Coolant in the oil is typically found with a major blow out, like the head gasket is pukeing coolant in to the cylinder. So one would find coolant upon removing the spark plugs and trying to do a compression test.
So some other hints for finding cooling leaking into the oil pan. Put a dye into the coolant, use a cooling system pressure tester, remove the valve cover and look for the dye. I have found the casting broken around the plugs in the valley of the cylinder head, leaking cooling between the front timing cover. And then If I could not find any other place, remove the oil pan and look for dye. If not then suspect the oil cooler. But the oil pressure is usually higher than coolant, so usually oil gets into the cooling system, not really the other way around. Lots of work to sometimes find a coolant leak. Anyhow good luck with this.
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