rimasl2
12-01-2006, 03:07 PM
I would like to post some observations and results regarding the rebuild of my air-intake manifold on my 1995 740i (E38 body ; M60 engine). A lot of the info. about what to check came from this board which I appreciated greatly. Its why I thought I would write this up so that maybe it can help add to the knowledge base.
While there are differences between the M60 engine and later M62's, the similarities are greater than the differences. As near as I can tell, the M62 engine was put into production in February of 1996 for the E38 body. All E38 bodies manufactured before that date were M60's.
In case anyone is wondering what the air-intake-manifold is, click here and check out part #1 (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=11_1426&hg=11&fg=40).
ONE NOTE: There are many references to the "OSV valve" or "OSV Plate" thoughout the forums where the reference is to part #2 in the diagram above. Its really incorrect to call the plate by that name. The OSV valve is located inside the crankcase of the engine at the front. The plate everyone refers to at the rear of the air-intake-manifold is really the PCV valve (positive-crankcase-ventilation). In this writeup, I refer to that plate by its correct name, the "PCV valve".
==================
Symptoms of My Car
==================
I've got 112k miles on the car. Generally the car ran well, but things didn't feel right. The car didn't have the instant power from a stop. Instead there was a very very slight lag when the accelerator was hit. Gas mileage was OK, about 16.5, but I think it had gone down about a mile/gallon over the last several years.
Recently, the check-engine-light (CEL) had begun flickering on and the idle was rough with some misses when cold. When cold, the CEL would generally flicker on when de-accelerating from about 30mph. If I gassed the accelerator pedal, the light would go off. Once warmed up, I'd never see the CEL. Error codes from a PEAK showed 0065 (output stage group #2), 00C9 (Lambda Control #1), 00CB (Lambda Control #2). If I reset the codes, they wouldn't re-appear until the next morning, when the car started from cold.
I did a couple of things:
1. replaced both my O2 sensors (the M60 engine only has 2, M62's have 4). This seemed to pick my gas mileage back up to 17.3 or so.
2. I could flick my finger against my Mass-Air-Flow sensor (MAF) and cause the car to stall (at idle). I replaced the MAF and could no longer stall the car, but it didn't seem to fix anything with regard to the running of the car. Also, I performed ohm checks on the good and "bad" MAF. This is what I observed:
(checks performed at about 65 degrees F)
MAF pins
=======
1-3 good MAF = 1.58K ; bad MAF = 1.62K
3-1 good = 1.58K ; bad = 1.62K
2-4 good = 241.2K ; bad = 300.5K
4-2 good = 238.2K ; bad = 294.1K
I can't say that ohm checks are necessarily a good indication in my case of a bad MAF.
After replacing the two items above, I was still left with the CEL light flicker when the engine was cold and the rough idle.
The next step was to look at vacuum leaks.
============================
Some Vacuum Leak Diagnostics
============================
Here is what I observed in finally deciding to rebuild the air-intake-manifold:
1. Oil dipstick test: I had a very slight amount of air being pulled into my dipstick tube. Some posts I had seen seemed to indicate that if you had an air-leak, or a bad PCV valve, that the air being sucked into the dipstick tube would be very dramatic and noticeable. Mine was barely noticeable. I wasn't sure there was a problem, but I wasn't sure it was correct.
2. PCV valve test: This test was one I came up with on my own. There is a small air breather hole on the bottom of the PCV valve plate (see photo #1). You can cover it with a single finger. When I covered this hole while the engine was running, the engine would shake convulsively and accelerate, then slow down to almost a stall and cycle like that very rapidly. This didn't seem correct, and in fact when I did have everything back together again with a new PCV valve installed, the engine remained rock-steady when that hole was covered while idling......so I think covering the hole is a good indication of an overall vacuum leak somewhere in the system. Possibly it is only an indication of a bad PCV valve, but when I did finally take it apart, the PCV valve looked whole, but it was very carboned up.
photo #1 - PCV Valve Test - you can cover this small vent hole with the engine idling by reaching in back of the engine. If, when you cover the hole with your finger, you get a lot of engine surging, it is a possible indication of either an air-intake-manifold leak, or a bad PCV valve....disclaimer: this observation is a sample of one only (my car before and after an air-intake-manifold rebuild)
http://vi-pc.com/EBAY/auto_forums/bmw/pcv_valve/pcv_valve.jpg
3. Carburetor Spray test: I could not get the engine to change idle speed with carburetor spray.
4. Cold engine test: I already mentioned this as a symptom, but it needs to be placed here. For sure if you're seeing a CEL light flicker when cold along with rough idle, its a pretty good bet, that there is a vacuum leak somewhere. Early vacuum leaks, will seal once the engine warms up. When they go really bad, they won't seal at operating temperature either.
5. Slight Lag when accelerating: The very very slight lag wasn't even a symptom I was sure about. Only after the rebuild, could I confirm that I had had a slightly lean condition from a vacuum leak.
Finally, I decided to take the plunge and do the rebuild. There was no hard evidence of a failure, just an accumulation of observations. The one condition that forced me into taking action was the CEL and rough idle when cold as I really wanted to get that fixed.
===========================================
A few easy checks before starting a rebuild
===========================================
As I did the rebuild, I saw a few things that could be done, or checked, without a rebuild. Maybe some individuals will only have one of these issues and so its worth checking first.
1. Rubber cap on throttle body: see part #8 here (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=13_0382&hg=13&fg=15). This is a rubber cap about 1/2" in diameter. It actually faces to the front of the car (unlike the diagram) and is located at about 5 o'clock below the main 3" throttle opening. Mine was hard as a rock (oxidized) and had cracked and I am sure was causing a small vacuum leak.
http://vi-pc.com/EBAY/auto_forums/bmw/pcv_valve/throttle_body_rubber_cap.jpg
2. Carbon buildup on the throttle intake: The 3" opening on the throttle intake body as well as the idle intake valve (part #9 here) (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=13_0384&hg=13&fg=15) can get very carboned up. You can remove the idle intake valve and clean it with carburetor cleaner. The 3" throttle throat can actually keep the throttle plate from closing as was the case with mine.
================================================== ===========
Verbal description of disassembly of the air-intake manifold
================================================== ===========
That's about it. Below is a verbal description of taking apart and cleaning the air-intake manifold. There are also some writeups at e38.org (http://www.e38.org). Look for either "OSV" or "Oil Separator".
===============
Items replaced:
===============
1. Rear cover PCV valve on air-intake manifold (see #2 (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=11_1426&hg=11&fg=40))
2. Vent pipe see #7 (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=11_1291&hg=11&fg=15)
3. rubber cap on throttle body (part #8 (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=13_0382&hg=13&fg=15))
4. 4ea. "eyeglass" gaskets see #9 (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=11_1426&hg=11&fg=40)
5. front and rear gaskets on air-intake-manifold
6. replaced all E30 torx head bolts on front and rear with 6mm x 25mm (1mm pitch 10.9 hardness) hex bolts
7. had fuel-injectors cleaned at http://www.witchhunter.com/ this really seemed worthwhile. turnaround was about 5 days (my ship to my receive). they cleaned, checked and replaced O-rings and gave a full report. My fuel-injector fuel throughput differed by almost 5% when received by them and differed by < 1% after re-build.
=========================
some notes on the rebuild
=========================
1. the removal of the 13ea E30 torx head bolts, that are located on the front and rear of the air-intake-manifold, are a bitch. Clean the inside of the heads with a knife and engine de-greaser first to get the tool seated. If all else fails, buy a good vise grips.
2. the removal of the small wires holding the valve electronics boxes to the fuel-injectors is very diffcult. If you just pull, they will come off and break some of the plastic while doing it. You need to remove by grabbing their ends where they loop around the plastic and separating and lowering them toward the fuel-injector body or pulling them toward the electronic boxes.
3. I tightened the front and rear bolts on the air-intake manifold to 140 inch-lbs as well as the 10ea nuts holding the air-intake manifold to the engine block
===========
Disassembly
===========
Taking the manifold off requires the removal (in order) of:
1. front MAF air duct to throttle, and idle-control-valve assemblies
2. fuel tank breather hose on front of the throttle assembly (just a 1/8" fuel pipe that sits at about 8-o-clock relative to the 3" throttle input).
3. throttle cables (removing the bracket holding the 2ea. throttle cables does the job)
4. 2ea. electronics boxes on each cylinder head. Pretty straightforward. You need to remove connectors all over the place. Just remember where they go back. When you finally get to the point where you're going to lift the boxes up from the fuel injector connectors, be careful. There are small metal wires which need to be removed from each fuel injector connector 1st. When all is said and done, the two electronics boxes will fold over to the passenger side of the engine compartment (they will never be removed completely from the car).
5. auxiliary brake vacuum pipe on rear of intake manifold as well as the fuel pressure regulator overflow pipe on the passenger side of the fuel rail going to the same rear plate
6. fuel rail and fuel injectors
7. 10ea. air intake manifold bolts.
8. once the air intake manifold bolts are out, the air intake manifold can slide to the rear of the engine compartment about 1/2" and clip #10 here (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=11_1291&hg=11&fg=15) can be removed. After the clip is off, the air intake manifold can be lifted off the engine.
Photo - engine compartment with air-intake-manifold removed
Notice the two each electronic boxes that mount to the valve boxes are pulled to the passenger side of the car.
http://www.vi-pc.com/EBAY/auto_forums/bmw/pcv_valve/engine_compartment.jpg
======================
Some results after the rebuild
======================
1. No air entering the dipstick. Actually, I think the air is very slightly positive now.
2. When I cover the small hole at the bottom of the PCV valve, the engine idle doesn't change at all.
3. The CEL and rough idle when cold are gone. In fact the engine is silky smooth at idle when cold.
4. Power from a stop is instantaneous. No lag whatsoever.
5. Overall glide of the car, is more positive. Before I seemed to have engine de-acceleration when I took the foot off the pedal. Now the engine seems to allow the car to glide along more or less at speed.
6. Beautifully smooth idle overall.
7. Gas mileage ???? will post with an update.
In the end, I can't say what exactly was wrong, but I believe it was just an accumulation of small things in a 11 year old car that included:
1. Bad rubber cap on throttle body
2. gummed up PCV valve
3. 2ea. rear most eyeglass gaskets on the air-intake manifold were definitely leaking as there was oil in the valley.
4. very gummed up fuel injectors and uneven spray
5. carboned up 3" throttle body opening that wasn't allowing the throttle plate to close
6. possible gummed up idle control valve.
While there are differences between the M60 engine and later M62's, the similarities are greater than the differences. As near as I can tell, the M62 engine was put into production in February of 1996 for the E38 body. All E38 bodies manufactured before that date were M60's.
In case anyone is wondering what the air-intake-manifold is, click here and check out part #1 (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=11_1426&hg=11&fg=40).
ONE NOTE: There are many references to the "OSV valve" or "OSV Plate" thoughout the forums where the reference is to part #2 in the diagram above. Its really incorrect to call the plate by that name. The OSV valve is located inside the crankcase of the engine at the front. The plate everyone refers to at the rear of the air-intake-manifold is really the PCV valve (positive-crankcase-ventilation). In this writeup, I refer to that plate by its correct name, the "PCV valve".
==================
Symptoms of My Car
==================
I've got 112k miles on the car. Generally the car ran well, but things didn't feel right. The car didn't have the instant power from a stop. Instead there was a very very slight lag when the accelerator was hit. Gas mileage was OK, about 16.5, but I think it had gone down about a mile/gallon over the last several years.
Recently, the check-engine-light (CEL) had begun flickering on and the idle was rough with some misses when cold. When cold, the CEL would generally flicker on when de-accelerating from about 30mph. If I gassed the accelerator pedal, the light would go off. Once warmed up, I'd never see the CEL. Error codes from a PEAK showed 0065 (output stage group #2), 00C9 (Lambda Control #1), 00CB (Lambda Control #2). If I reset the codes, they wouldn't re-appear until the next morning, when the car started from cold.
I did a couple of things:
1. replaced both my O2 sensors (the M60 engine only has 2, M62's have 4). This seemed to pick my gas mileage back up to 17.3 or so.
2. I could flick my finger against my Mass-Air-Flow sensor (MAF) and cause the car to stall (at idle). I replaced the MAF and could no longer stall the car, but it didn't seem to fix anything with regard to the running of the car. Also, I performed ohm checks on the good and "bad" MAF. This is what I observed:
(checks performed at about 65 degrees F)
MAF pins
=======
1-3 good MAF = 1.58K ; bad MAF = 1.62K
3-1 good = 1.58K ; bad = 1.62K
2-4 good = 241.2K ; bad = 300.5K
4-2 good = 238.2K ; bad = 294.1K
I can't say that ohm checks are necessarily a good indication in my case of a bad MAF.
After replacing the two items above, I was still left with the CEL light flicker when the engine was cold and the rough idle.
The next step was to look at vacuum leaks.
============================
Some Vacuum Leak Diagnostics
============================
Here is what I observed in finally deciding to rebuild the air-intake-manifold:
1. Oil dipstick test: I had a very slight amount of air being pulled into my dipstick tube. Some posts I had seen seemed to indicate that if you had an air-leak, or a bad PCV valve, that the air being sucked into the dipstick tube would be very dramatic and noticeable. Mine was barely noticeable. I wasn't sure there was a problem, but I wasn't sure it was correct.
2. PCV valve test: This test was one I came up with on my own. There is a small air breather hole on the bottom of the PCV valve plate (see photo #1). You can cover it with a single finger. When I covered this hole while the engine was running, the engine would shake convulsively and accelerate, then slow down to almost a stall and cycle like that very rapidly. This didn't seem correct, and in fact when I did have everything back together again with a new PCV valve installed, the engine remained rock-steady when that hole was covered while idling......so I think covering the hole is a good indication of an overall vacuum leak somewhere in the system. Possibly it is only an indication of a bad PCV valve, but when I did finally take it apart, the PCV valve looked whole, but it was very carboned up.
photo #1 - PCV Valve Test - you can cover this small vent hole with the engine idling by reaching in back of the engine. If, when you cover the hole with your finger, you get a lot of engine surging, it is a possible indication of either an air-intake-manifold leak, or a bad PCV valve....disclaimer: this observation is a sample of one only (my car before and after an air-intake-manifold rebuild)
http://vi-pc.com/EBAY/auto_forums/bmw/pcv_valve/pcv_valve.jpg
3. Carburetor Spray test: I could not get the engine to change idle speed with carburetor spray.
4. Cold engine test: I already mentioned this as a symptom, but it needs to be placed here. For sure if you're seeing a CEL light flicker when cold along with rough idle, its a pretty good bet, that there is a vacuum leak somewhere. Early vacuum leaks, will seal once the engine warms up. When they go really bad, they won't seal at operating temperature either.
5. Slight Lag when accelerating: The very very slight lag wasn't even a symptom I was sure about. Only after the rebuild, could I confirm that I had had a slightly lean condition from a vacuum leak.
Finally, I decided to take the plunge and do the rebuild. There was no hard evidence of a failure, just an accumulation of observations. The one condition that forced me into taking action was the CEL and rough idle when cold as I really wanted to get that fixed.
===========================================
A few easy checks before starting a rebuild
===========================================
As I did the rebuild, I saw a few things that could be done, or checked, without a rebuild. Maybe some individuals will only have one of these issues and so its worth checking first.
1. Rubber cap on throttle body: see part #8 here (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=13_0382&hg=13&fg=15). This is a rubber cap about 1/2" in diameter. It actually faces to the front of the car (unlike the diagram) and is located at about 5 o'clock below the main 3" throttle opening. Mine was hard as a rock (oxidized) and had cracked and I am sure was causing a small vacuum leak.
http://vi-pc.com/EBAY/auto_forums/bmw/pcv_valve/throttle_body_rubber_cap.jpg
2. Carbon buildup on the throttle intake: The 3" opening on the throttle intake body as well as the idle intake valve (part #9 here) (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=13_0384&hg=13&fg=15) can get very carboned up. You can remove the idle intake valve and clean it with carburetor cleaner. The 3" throttle throat can actually keep the throttle plate from closing as was the case with mine.
================================================== ===========
Verbal description of disassembly of the air-intake manifold
================================================== ===========
That's about it. Below is a verbal description of taking apart and cleaning the air-intake manifold. There are also some writeups at e38.org (http://www.e38.org). Look for either "OSV" or "Oil Separator".
===============
Items replaced:
===============
1. Rear cover PCV valve on air-intake manifold (see #2 (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=11_1426&hg=11&fg=40))
2. Vent pipe see #7 (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=11_1291&hg=11&fg=15)
3. rubber cap on throttle body (part #8 (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=13_0382&hg=13&fg=15))
4. 4ea. "eyeglass" gaskets see #9 (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=11_1426&hg=11&fg=40)
5. front and rear gaskets on air-intake-manifold
6. replaced all E30 torx head bolts on front and rear with 6mm x 25mm (1mm pitch 10.9 hardness) hex bolts
7. had fuel-injectors cleaned at http://www.witchhunter.com/ this really seemed worthwhile. turnaround was about 5 days (my ship to my receive). they cleaned, checked and replaced O-rings and gave a full report. My fuel-injector fuel throughput differed by almost 5% when received by them and differed by < 1% after re-build.
=========================
some notes on the rebuild
=========================
1. the removal of the 13ea E30 torx head bolts, that are located on the front and rear of the air-intake-manifold, are a bitch. Clean the inside of the heads with a knife and engine de-greaser first to get the tool seated. If all else fails, buy a good vise grips.
2. the removal of the small wires holding the valve electronics boxes to the fuel-injectors is very diffcult. If you just pull, they will come off and break some of the plastic while doing it. You need to remove by grabbing their ends where they loop around the plastic and separating and lowering them toward the fuel-injector body or pulling them toward the electronic boxes.
3. I tightened the front and rear bolts on the air-intake manifold to 140 inch-lbs as well as the 10ea nuts holding the air-intake manifold to the engine block
===========
Disassembly
===========
Taking the manifold off requires the removal (in order) of:
1. front MAF air duct to throttle, and idle-control-valve assemblies
2. fuel tank breather hose on front of the throttle assembly (just a 1/8" fuel pipe that sits at about 8-o-clock relative to the 3" throttle input).
3. throttle cables (removing the bracket holding the 2ea. throttle cables does the job)
4. 2ea. electronics boxes on each cylinder head. Pretty straightforward. You need to remove connectors all over the place. Just remember where they go back. When you finally get to the point where you're going to lift the boxes up from the fuel injector connectors, be careful. There are small metal wires which need to be removed from each fuel injector connector 1st. When all is said and done, the two electronics boxes will fold over to the passenger side of the engine compartment (they will never be removed completely from the car).
5. auxiliary brake vacuum pipe on rear of intake manifold as well as the fuel pressure regulator overflow pipe on the passenger side of the fuel rail going to the same rear plate
6. fuel rail and fuel injectors
7. 10ea. air intake manifold bolts.
8. once the air intake manifold bolts are out, the air intake manifold can slide to the rear of the engine compartment about 1/2" and clip #10 here (http://www.realoem.com/bmw/showparts.do?model=GF63&mospid=47526&btnr=11_1291&hg=11&fg=15) can be removed. After the clip is off, the air intake manifold can be lifted off the engine.
Photo - engine compartment with air-intake-manifold removed
Notice the two each electronic boxes that mount to the valve boxes are pulled to the passenger side of the car.
http://www.vi-pc.com/EBAY/auto_forums/bmw/pcv_valve/engine_compartment.jpg
======================
Some results after the rebuild
======================
1. No air entering the dipstick. Actually, I think the air is very slightly positive now.
2. When I cover the small hole at the bottom of the PCV valve, the engine idle doesn't change at all.
3. The CEL and rough idle when cold are gone. In fact the engine is silky smooth at idle when cold.
4. Power from a stop is instantaneous. No lag whatsoever.
5. Overall glide of the car, is more positive. Before I seemed to have engine de-acceleration when I took the foot off the pedal. Now the engine seems to allow the car to glide along more or less at speed.
6. Beautifully smooth idle overall.
7. Gas mileage ???? will post with an update.
In the end, I can't say what exactly was wrong, but I believe it was just an accumulation of small things in a 11 year old car that included:
1. Bad rubber cap on throttle body
2. gummed up PCV valve
3. 2ea. rear most eyeglass gaskets on the air-intake manifold were definitely leaking as there was oil in the valley.
4. very gummed up fuel injectors and uneven spray
5. carboned up 3" throttle body opening that wasn't allowing the throttle plate to close
6. possible gummed up idle control valve.