Compression test results - Page 2 - Alfa Romeo Bulletin Board & Forums
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post #16 of 35 (permalink) Old 09-25-2018, 05:56 PM
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All this is nonsense...Chas H said it all in post #7
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post #17 of 35 (permalink) Old 09-25-2018, 08:18 PM
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Quote:
Originally Posted by ARwrench View Post
All this is nonsense...Chas H said it all in post #7 <img src="http://www.alfabb.com/bb/forums/images/AlfaBB_2015/smilies/tango_face_wink.png" border="0" alt="" title="Wink" class="inlineimg" />
Heck good point!
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post #18 of 35 (permalink) Old 09-26-2018, 05:14 AM
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Closed throttle DOES make the resulting reading lower!!

Frankly, even-ish reading between cylinders is more saying "general wear" than a cracked ring (then one cylinder is dramatically different). Or head gasket failure - that's typically uneven pressures.

Looking at the original question: Oil lost.

1) Is there OIL in the ANTIFREEZE??
2) Cardboard under the car - Oil puddle anywhere??

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post #19 of 35 (permalink) Old 09-26-2018, 06:21 AM
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Originally Posted by bruce1976spider View Post
Closed throttle DOES make the resulting reading lower!!
Well, of course it does. And the reason is quite simple. An internal combustion engine is a pump. An air pump to be more precise. The output is therefore dependent upon, among other things, it's input. The lower the input, the lower the output. This is why closed throttle compression readings are ALWAYS lower then WOT readings.

The dry/wet compression numbers do tell a bit of a story. The reported symptom is 250 miles/quart of oil. If all of this oil was coming up past the oil control rings, the cylinders walls would be oil coated. This could give false high compression readings as the dry test is effectively a wet test. However, the delta between the dry and wet test readings is too high. Therefore, the oil rings are NOT the major source for the oil consumption.
Moot point really as the dry/wet readings indicate compression problems anyway.

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post #20 of 35 (permalink) Old 09-26-2018, 07:13 AM
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Quote:
Originally Posted by alfaparticle View Post
A throttle opening of 10% will supply sufficient air for the engine to rev at 6000 rpm. That is about 200 times higher than the engine is spinning during a compression test. The WOT requirement is an old wives tale.
Ed, I'd like to challenge you on this. Running the test with the throttle wide open makes for consistency across each of the cylinders. Rhetorically, how can anyone know that they are consistently holding the throttle in the exact same position if it's not wide open. As Jim stated, it's all about moving air through the cylinders. More air equals more horsepower.

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post #21 of 35 (permalink) Old 09-26-2018, 08:46 AM
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Car is new to you.....so, by chance could engine have been re built recently? I used minimum a quart every 500 miles for 10,000 miles after mine was rebuilt....now, almost suddenly ...using almost nothing....took mine awhile to get seated I guess... I use Castrol GTX 20-50

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post #22 of 35 (permalink) Old 09-26-2018, 08:51 AM
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on the UK forum a guy posted his compression readings and thought he had a looming problem, I'll quote:
"Firstly can I say I'm a total novice mechanic.
I was concerned that my 1300 Super was hesitant below 2000 revs. I decided to run a compression test and the results were not good.
1: 107
2: 90
3: 110
4: 137
I have to admit that I didn't warm up the engine, did not touch the throttle during the test and the test was dry. is it worth re-testing..."

I told him his readings meant nothing and to retest 'HOT, WOT and all plugs out':

then he got (quote):

"I have a new set of compression results from a warm engine, throttle open . I'm pleased to say the numbers are completely different to cold engine throttle closed.
1) Dry: 195 Wet: 200
2) Dry: 195 Wet: 200
3) Dry: 190 Wet: 190
4) Dry: 195 Wet: 205 "

he was a pretty happy bunny and could now concentrate on the next problem

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #23 of 35 (permalink) Old 09-26-2018, 09:02 AM
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Many cars ago, I owned a 16 valve VW Jetta. I took it to an independent VW/Audi shop because I could not figure out why it was running poorly at idle.

The employee did a compression test and told me my car needed a valve job. Why? It has low compression. I challenged him and asked how he ran the test. He ran it cold with the throttle closed. I came and got my car and paid my bill. On the way home, I bought a compression testor. I ran it dry/wet with the throttle wide open. The car had excellent compression. I went back to the shop and demanded that the employee re-run the test. He did, this time with the throttle wide open as per my instruction. The results were excellent. He said, "you did something to your car." ***? I got my money back.

Later, I figured out the issue, it was the differential pressure regulator.

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post #24 of 35 (permalink) Old 09-27-2018, 10:30 AM
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I am going to go out on a limb here and say it appears that your oil consumption is due to something other than your rings or valves. If that much oil was blowing past your rings you should see black or blue oil smoke out the exhaust. Does the exhaust smell like oil burning? That is normally one of the simplest tests when your burning that much oil.

I had a small issue with oil consumption on mine and getting a proper tune up made a huge difference. Mine is a 77 spica injected car that was running way to rich and leaving black plugs after just a few hundred miles. I took it to the Alfa guru in my area (Santa Barbara, CA). He tuned it and got it through smog. Since then my oil consumption has dropped by about half down to half a quart or less every 3000 miles or so.

To me it's one simple step at a time. Get it tuned, look for leaks (those would be big leaks), take a sniff of your exhaust. Make sure your dipstick fits correctly each time you measure it (I know that sounds dumb but I have seen people who don't seat the dip stick properly each time they measure it resulting in an incorrect reading). Make sure you are checking the oil on flat ground each time (seen that too). Do a proper compression test. Stand behind the car with it in neutral and have somebody run it up to 4000 rpm and back down a few times do you see anything coming out of the exhaust? If your running so rich that your plugs are black you should see and smell something coming out of the exhaust.

Good luck

Somebody mentioned engine break in. That is certainly a possibility if yours has been recently rebuilt. Rings and valves take time to seat.
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post #25 of 35 (permalink) Old 01-07-2019, 10:15 AM Thread Starter
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So after thinking about the problem more, i came to the conclusion that the oil wasn't being consumed as the car does not smoke at all. In addition, I'd lose the most oil after high RPM highway runs. Oil had to be leaking out!

So I finally put florescent dye in the oil, and did a high RPM highway run. Low and behold, the low oil sender had a ton of dye below it:



Just ordered a new sender... Hopefully that will do the trick!


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post #26 of 35 (permalink) Old 01-07-2019, 12:01 PM
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great photo to illustrate just how useful that dye can be!


edit: oh, and remember the sender has a small copper seal washer.......new senders hardly ever come with them, so either get a new one or clean up and re-anneal the old one.

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.

Last edited by spiderserie4; 01-07-2019 at 12:08 PM.
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post #27 of 35 (permalink) Old 01-07-2019, 12:11 PM Thread Starter
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What the picture dosen,'t show is how wet the area was. I usually drive the car about 8 miles around town. I suspect with the lower revs and lower oil pressure, the leak is much less severe, but at high revs and high oil pressure it really flows and it only leaks when the car is running, which would explain the lack of a big oil puddle in the garage.

My only concern is that when i tried to tighten the sender, it kept rotating... Hopfully the threads on the block aren't stripped!

Plan on using some Permatex thread sealer on the new sender


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post #28 of 35 (permalink) Old 01-07-2019, 12:16 PM Thread Starter
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So when i checked the parts manual it showed a washer used on the sender for the dash guage, but did not show a washer for the low oil sender (idiot light), which is what I am replacing, I didn't see any of these washers for sale by any of the vendors... any suggestion for a source if i do in fact need one?


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post #29 of 35 (permalink) Old 01-07-2019, 12:20 PM
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Quote:
Originally Posted by Crowbar44 View Post
My only concern is that when i tried to tighten the sender, it kept rotating... Hopfully the threads on the block aren't stripped!
I'm afraid it sounds like they are, and that was probably the leak in the first place, a PO overtightening things, or maybe not using the copper seal ring....

to me it looked like the oil pressure gauge sender (with washer) from here, not the idiot light sender (no washer on this as the threads are coned / edit: tapered!)
The idiot light sender is on the alternator side, the gauge sender is above the starter motor....which is it in that photo?

You might be able to get away with some sealer as long as some of the threads are holding.........if it goes around and around by hand, I would not trust it at all.
Personally it'd scare me thinking one day the thing might fall out altogether..

Only real repair (if it is the gauge sender) is a heli coil.......but getting down there is not gonna be easy, if at all.
If indeed it is the idiot light sender, then sealant should do it.....but it still shouldn't turn round 'n round, as the threads being coned, get tighter and tighter.

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.

Last edited by spiderserie4; 01-07-2019 at 12:56 PM.
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post #30 of 35 (permalink) Old 01-07-2019, 12:22 PM
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Quote:
Originally Posted by ossodiseppia View Post
Many cars ago, I owned a 16 valve VW Jetta. I took it to an independent VW/Audi shop because I could not figure out why it was running poorly at idle.

The employee did a compression test and told me my car needed a valve job. Why? It has low compression. I challenged him and asked how he ran the test. He ran it cold with the throttle closed. I came and got my car and paid my bill. On the way home, I bought a compression testor. I ran it dry/wet with the throttle wide open. The car had excellent compression. I went back to the shop and demanded that the employee re-run the test. He did, this time with the throttle wide open as per my instruction. The results were excellent. He said, "you did something to your car." ***? I got my money back.

Later, I figured out the issue, it was the differential pressure regulator.
OMG!

Pete

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