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Engine Specific Info and Questions => IDI Engine => Topic started by: rs899 on September 05, 2012, 11:46:55 am
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The engine on my Caddy has about 200k miles on its last rebuild. With a good starter, it starts instantly. Compression is 400 psi across all cylinders .
But all is not well. It burns copious amounts of oil, even with a splash shield over the cam and a Mercedes oil separator installed. Maybe a quart every 500 miles
It’s an 11mm block and I don’t think it would be easy to find the largest size O/S pistons ( and I have a couple of better blocks anyway)
Would a re-ring help? With 11mm block I may be tempting fate- should I just run it until it …runs away?
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Well if it is burning that much and the compression is that high... I'd be doubting one of your readings.
Mainly the compression, because you know how much oil you have to put in.
I don't know if a serious oil burner will make near perfect compression.. Also did you do this comp test hot or cold?
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I have an AAZ that has excellent compression and yet uses about as much oil as diesel. Seriously. Like a quart per 50 miles.
To the OP, run it to a catch can. I made one out of ABS with a plumb-quick fitting on the top drilled to accept a crank vent filter from my FLAPS. Then it gets poured back in... Plan on a rebuild soon.
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Oh, interesting. These engines cease to amaze. What do you think the cause of the extreme blow-by is then?
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If the compression is that good, check the cylinder head. I bet it is in need of seals at the least, if not completely gone through. With 400psi, I wouldn't re ring as you shouldn't gain much, if maybe replace the oil scraping rings to the 3 piece???
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I suspect that the oil control rings on my AAZ are either stuck or broken. Certainly valve stem seals could be part of it. A full rebuild is in it's very near future and so the specific cause is just academic.
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my queston.... you fill when 1 qt low or 1/2 qt low?? 1st 1/2 burns way faster then 2nd 1/2 why i ask...
queston 2.. turbo? i only ask that as if the oil return line is too low on the pan it will suck oil down... has to be above the oil level in the pan...
queston 3... what vac pump.. old diafram style with vent off front of block... will boost oil usage... remove block vent.. use pvc style breather filter on the pump.. and plumb catch can into block vent hole.. you would be suprised at how much this trick helps...
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CRAMP5, I'm not sure who you're asking, but that AAZ of mine is in a vanagon and the oil does enter the pan below the oil level just like all 200,000+ stock VW vanagon turbo-diesels sold in other markets. I have also owned and worked on many that had a similar oil drain below the oil level in the pan without any oil consumption issues.
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i have always wondered that on a vanagon set up... but i think its more oil level when running...
how this topic came up to me back inn 96.. .pree interwebz... when i installed my used bae turbo kit i put the drain too low... sucked it down all of a sudden when i never had issues prior.. someone told me my return was too low.. moved it up issue resolved..
and my questons were for the op... a few other ideas vs rings/seals/guids
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To the OP, run it to a catch can.
I am basically doing that already. The MB 240D oil separator runs back to the port on the block that was formerly used by the original vacuum pump. I have the later piston type vacuum pump on it now.
my queston.... you fill when 1 qt low or 1/2 qt low?? 1st 1/2 burns way faster then 2nd 1/2 why i ask...
I usually refill when it gets close to the bottom line on the stick, and then only go as high as the halfway mark.
queston 2.. turbo? i only ask that as if the oil return line is too low on the pan it will suck oil down... has to be above the oil level in the pan..
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No turbo, 1.6 IDI NA
queston 3... what vac pump.. old diafram style with vent off front of block... will boost oil usage... remove block vent.. use pvc style breather filter on the pump.. and plumb catch can into block vent hole.. you would be suprised at how much this trick helps...
New style piston vacuum pump.
I am pretty sure my compression gauge is accurate as it literally lights off in less than a revolution when cold.
I know it could use valve guide seals, but I question whether that contributes all that much to the consumption.
Of course, it needs a rebuild, but I wouldn't rebuild this block anyway as it already has oversize pistions. I would likely take them out and move them to an original bore block, but then there's hundreds of dollars of machinist/parts cost and a lot of time.
If I felt there was a chance that I could re-ring it, and maybe rebuild a head ( which I can do for basically nothing, including new guides and seals) I might do that. Otherwise, just keep running it. It's really just going to be a third stringer to my Jetta and Cabriolet ( once that is re-engined). I am really curious what could be doing this with such good compression. Could a couple of oil rings be broken ?
I just hate to spend $3/week on oil when I have to drive this...
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If you have a catch can that is actively catching all the oil out of the blow-by and you are still using that much oil, then there may be nothing left to do but rebuild. Probably just the head though as it would seem.
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Is there any way on a diesel to tell, without pulling it completely apart, if it's the rings or the valves?
I wouldn't mind too much at all reworking the head, but reringing in situ I would rather avoid (BTDT).
I didn't think it would be possible that valves could contribute that much to consumption.
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Well it is a 4 stroke engine, the fuel type doesn't matter so I would do a leak down test. You will hear where the air is escaping.
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I don't think that's going to tell me anything, unless my compression tester is completely wrong ( but my ear tells me it's not since the engine starts so well).
The valves and rings are sealing well enough to produce good compression. When the valves are closed it seals OK and it's not burning through the valves then. If it's valves , it's burning when the valve is open.
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My jetta engine had numbers just like that and close to same oil burning, although I did have some drips from the valve cover that I could not stop. I also made a pvc type catch can inline with the stock setup and ran a low drain port down to where the block cover was. I was getting bad blowby on that engine and it was trying to push oil out where it could, although never out the dipstick.
I broke the engine down and the bore readings said it needed to be bored out with some slight eggshape going on.
This car was involved in one overheating incident when a coolant hose broke and a family member drove it until it locked up. I patched it on the road and slowly drove it home 20 miles but had to pull over every minute to refill with water, the head gasket had went and it would try and overheat. Surprisingly that head seems ok to the eye and basic measurements with a feeler but I haven't had it checked out yet.
I also didn't have issues starting the car down into the teens on the first glowplug cycle.
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I don't think that's going to tell me anything, unless my compression tester is completely wrong ( but my ear tells me it's not since the engine starts so well).
Advanced timing can easily mask compression issues. I wouldn't assume the compression is good because the car starts well. There's a reason a lot of people on the site time their motors above 1.00mm
Like you said though, a leak down test isn't going to show you much. Valve stem seals can be done in the car so that would be a nice easy/cheap place to start.
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I don't think that's going to tell me anything, unless my compression tester is completely wrong ( but my ear tells me it's not since the engine starts so well).
Advanced timing can easily mask compression issues. I wouldn't assume the compression is good because the car starts well. There's a reason a lot of people on the site time their motors above 1.00mm
Like you said though, a leak down test isn't going to show you much. Valve stem seals can be done in the car so that would be a nice easy/cheap place to start.
valve seals can make ALOT of blowby in an otherwise TIGHT engine..
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I don't think that's going to tell me anything, unless my compression tester is completely wrong ( but my ear tells me it's not since the engine starts so well).
Advanced timing can easily mask compression issues. I wouldn't assume the compression is good because the car starts well. There's a reason a lot of people on the site time their motors above 1.00mm
Like you said though, a leak down test isn't going to show you much. Valve stem seals can be done in the car so that would be a nice easy/cheap place to start.
valve seals can make ALOT of blowby in an otherwise TIGHT engine..
That is what I am talking about. They can be torn or worn and you will lose a ton of oil.
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I guess I was under the impression that since a diesel has no natural vacuum, valve seal leakage was pretty minimal.
It's worth considering. I don't know how fiddly it is, though. I can barely get those keepers to cooperate when the head is on the bench.
I suppose you mark the flywheel or front pulley so you know where TDC is for all cylinders and have at it? Anyone done it on the car?
I just know if/when I try that I will find that the guides are real sloppy and then....pandora's box...
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I can imagine a pretty good gale of wind blowing up the valve stem from intake or exhaust manifold pressure if the stem seals were shot, but the pressure would send the oil out the crank vent rather than into the engine to be burned. If you are already running to a catch can, then I would think stem seals might not make much of a change. they're not going to hurt, tho.
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use some nice snotty grease for those pesky keepers..put it on em..and some on the valve stem too...stick em in place.just a lil hillfolk tip
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^^ Not so much that, but getting them oriented and seated on the stem in that little space while crunching down the spring. PITA.
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I have own a lot of these 1.6 & 1.9 diesels. One topic I am not seeing discussed is coolant temperatures.
I find that when I control the coolant temparature (and with a coolant based oil cooler) and therefore my oil temperatures, my engine do not use oil.
First start with a coolant blend. Water boils at 212 degrees Fahrenheit. 50-50 antifreeze will boil at 220. The recommended blend is 60% coolant & 40% water. 60-40 boils at 226 degree. 226-212=14 degrees.
Next for every 1lb of pressure added to coolant, 3 degees fahrenheit is add to the temp that coolant boils. Atipically the VW system uses a 7 psi cap. With tight hose connections and a good cap, the water would start boiling at 233 degree, 50-50 at 241, and the 60-40 would boil at 247 degrees.
So if 50-50 is 220 & 60-40 is 226, why not 80-20 or 100% antifreeze. Purer blend of coolant will affect the coolant based oil cooler. Blends above 50-50 and 60-40 will not cool the oil as well.
I have a 1.9TD in my Caddy, and the radiator is not large, because a big diesel radiator won't fit. My coolant temps are good. At first, I tried 5K mile oil changes and found no oil use. Then I tried 7K, and no oil usage. I now use 10K and still have no oil useage. I have all my diesels (10 vehicles) on a 10K oil change ritual, some on this diet for 200-400K.
Just did a 600 mile trip on I-95, running with traffic at 65-79 MPH and unless I gouged the throttle and stayed in it, my temp were just right of center. This oil change has 8500 miles and no oil useage.
We have to keep these engines cool.
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Another topic I am not seeing clarified is oil. I assure you that unless the oil is designed for diesel, consumption will occur. Too thin oil will be consumed. I have 10 on road diesels and near the same number off-road diesels for my farm. I buy top quality good oil, and due to my climate locaton 15-40 blend.
I can take any one of my well performing diesels and change to a cheap oil or gasser blend and I would guarantee oil consumption. If I go to 18-20K on oil changes, there will be consumption.
Review:
1. Overheating - expect oil consumption
2. Poor quality oil - expect oil consumption.
3. Extended oil changes- usage.
4. Leaks. Fix them.
Name-brand oils for NASCAR will kill a diesel. Go to a truckstop. See what truckers use. Go to a diesel shop. See what they use.
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What kind of air filter are you running, OP?
I tried using a cheaper air filter and I got a massive increase in oil consumption, to where it would need about a quart every 500 miles and the exhaust smelled of burning oil. This was right after I refurbished my head and turbo, so I was worried that a seal was leaking.
I then put a German (Mann Filter, I think) filter back on it, and the oil consumption seems to have largely disappeared. The cheaper filter had noticeably less material and looked like it wouldn't pass nearly as much air, and it became dirty quickly because there weren't as many pleats. My theory is that the cheap filter increased the vacuum between the filter and turbo, which was enough to suck oil out of the valve cover, even with the plastic baffle there.
I'm going to try something else too, which I'll post later, that should just slightly restrict the airflow in the breather and trap oil mist.
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i didnt read all the posts after mine,but i like the 80c thermostat over the 87c...just my 2 cents.....
80c is approx 180f,and 87c is approx 195f....195 imo doesnt give enough thermal reserve for those long hot days up hills at wot...i used to have the rad fan come on at 70mph up long hills cruisin rt80 thru pa with an 87c,but no prob with an 80c
i had an aux fan switch paralelled with the stock rad fan switch,and the lamp would come on in the switch telling me the fan was running but not by my switch...
also...motorad makes failsafe tstats for our vws also...if they fail,they fail open.....
water cools better than af....ive seen too strong a mix cause an overheat...
i do prefer dex cool or an = these days.......
50-50 mix is ok,but 40% coolant is better imo,except you canada guys..thats good for- 20f freeze point.....
throw some water wetter in there also...
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87° will result in better engine efficiency and will not cause overheating unless there is some other cooling system issue present. If there is some other cooling system issue, then the difference between the 80° thermostat and the 87° thermostat will mean an extra 1/2 second before boil over.