Hi all!
Like I mentioned in another another thread, I’m working on resealing the valve covers of my 97 SL600, and while at it, doing all the “while I’m there” preventive maintenance jobs. Wouldn’t want to do the same job twice in short succession.
A short recap on what’s been done before this is probably in order. Soon after I got the car in summer 2018 I realized there was a slight idle fluctuation that could be felt inside the car as an annoying vibration a V12 shouldn’t have. Initially the engine was also lacking a lot of power at high RPM. It didn’t feel much quicker than my old SL320. I replaced the ignition coils and spark plug boots, but the real issue turned out to be that the cats were clogged. After replacing them I finally got to meet the power reserve of the engine properly.
The vibration got worse, though, and last spring I had the engine and trans mounts replaced. Much better, but after a while I realized the problem was still there, just not as obvious. A while ago I replaced the fuel pressure regulator because the vacuum hose smelled of fuel. Still no change. New spark plugs (Bosch F8DC4). Nothing. But I did notice some oil in the spark plug wells, and being the perfectionist I am, I decided the next step was going to be pulling the intake manifold and valve covers. Maybe I’d stumble across the idle issue while at it.
I started this project last week. The first 2 hours went into removing everything from around the manifold: Throttle bodies, MAFs, air cleaners, vacuum hoses, ignition coils, wiring harness, and finally the fuel rail. The only thing that caused a little head scratching was the wire that goes to the AC compressor. But nothing special really.
The following day I took the injectors to be tested and cleaned if necessary. They all checked out, which was kind of disappointing because I hoped they might be the cause of my idle problem. The first column in the report below means leak test while pressurized, and the second one is the spray pattern.
All that was left was to unbolt the manifold itself, and the left brake booster vacuum line. It was a bit tough to get to but nothing too bad. The bolts were all easy to get to and gave in after spraying a little WD-40. You need to be very careful with the Allen bolts though as they strip easily.
In addition to the manifold bolts, you also need to remove the upper bolt of the right bank engine hoist bracket at the back of the engine. It’s a trivial detail but it almost made me shed a tear of joy to see how that bit was designed: On the left bank bracket, and that one only, there’s a slot that’s designed for reaching the bolt on the other side easily. You could reach it otherwise too, but it makes it a little easier. As an engineer, I found that a beautiful detail. After removing that bolt, the bracket bends just a little which makes it easier to wiggle the manifold out.
Speaking of the manifold, the WIS says something to the tune of “lift it to the side”, but I found that it came out by wiggling it up from the front. Once you get it past the power steering fluid reservoir, it comes right out.
After the manifold was out, the next step was to undo a couple of dozen bolts to get the valve covers out. I took them and the manifold to be glass bead blasted and powder coated, and I’m still waiting to get them back. Fingers crossed they’ll look nice.
The next step was to remove the flanges between the heads and the intake manifold. Nothing special there except some more unbolting, which was easy as this time I sprayed WD-40 the day before. As a result, the crankcase breather pipe on the bottom of the valley was exposed. To get to the knock sensors it needed to be removed, and I wanted to check it out anyway. It’s bolted to the head at the front and middle of the engine.
Once I got the breather pipe out, it seemed pretty clear what my idle problem was about. The wide plastic center part of the breather, the pressure damper, was cracked. And not by time or wear, but quite obviously because someone has been there before and forced it in place. I have no idea why, especially as all date stamped parts I’ve found down there seem to be originals, so it doesn’t seem like anyone has actually replaced anything before. Gaskets don’t have date stamps so I don’t know about them. In any case, the damper was leaking and it’s quite certainly a source of unmetered air and therefore the (or at least a) cause of my idle issue.
The bad news is that now I have to wait a couple of more weeks to get the replacement part. The pipe costs around 100-150 EUR depending on the seller. While at it, I also ordered the small coolant hose that connects the heads through the hoist brackets, and the hose that goes from the same place to the firewall (towards the heater core). And the O rings on the hoist brackets that act as pipe fittings.
Now that the breather was out, I was able to replace the knock sensors down in the valley. Nothing special there either. I had also decided to deal with the crankshaft position sensors while I had the access. The right bank sensor was readily accessible from above after the intake was off, but there’s no way you can reach the left one. It’s too tight between the firewall and head. However, after removing the upper firewall portion and the heater hose that goes from the back of the V to the firewall, the bolt is easily accessible with an extension.
The trick to removing and installing the sensor is to wiggle it by the cable through the back of the V valley with the plug connected. Before I figured that out I feared I couldn't do it at all, but in the end it was surprisingly easy. Careful with the cables with both the knock and crank sensors though - I’m told their insulation deteriorates and they’re unobtainium. I didn’t see any damage on mine though and the cables were flexible.
The last thing I did so far was to replace the two hoses between the tandem pump and power steering reservoir. Having done it, I think it would be possible to do even without removing the manifold, but it was certainly easier this way.
Here’s the list of parts I’ve ordered so far:
At this point I’m about 7-8 hours into the job, excluding all the studying online and with Alldata/WIS, figuring out what parts I need and getting them, and of course taking the parts to be painted and injectors to be tested. I’m working in a public parking facility where I have a permanent spot, so the time includes setting up before and cleaning up afterwards. The trunk is my toolbox and storage…
To be continued when I get the valve covers and/or the remaining parts I’ve ordered. Below is a teaser of the color options I was considering. I went with RR41. The color chart is that of some Finnish industrial company so you probably won't find the exact same color pretty much anywhere. It's called metallic dark silver and has some metal flakes. I'm an OEM kind of guy, but I don't mind a little refresh here, especially as I couldn't find an exact match to the original colors.
Like I mentioned in another another thread, I’m working on resealing the valve covers of my 97 SL600, and while at it, doing all the “while I’m there” preventive maintenance jobs. Wouldn’t want to do the same job twice in short succession.
A short recap on what’s been done before this is probably in order. Soon after I got the car in summer 2018 I realized there was a slight idle fluctuation that could be felt inside the car as an annoying vibration a V12 shouldn’t have. Initially the engine was also lacking a lot of power at high RPM. It didn’t feel much quicker than my old SL320. I replaced the ignition coils and spark plug boots, but the real issue turned out to be that the cats were clogged. After replacing them I finally got to meet the power reserve of the engine properly.
The vibration got worse, though, and last spring I had the engine and trans mounts replaced. Much better, but after a while I realized the problem was still there, just not as obvious. A while ago I replaced the fuel pressure regulator because the vacuum hose smelled of fuel. Still no change. New spark plugs (Bosch F8DC4). Nothing. But I did notice some oil in the spark plug wells, and being the perfectionist I am, I decided the next step was going to be pulling the intake manifold and valve covers. Maybe I’d stumble across the idle issue while at it.
I started this project last week. The first 2 hours went into removing everything from around the manifold: Throttle bodies, MAFs, air cleaners, vacuum hoses, ignition coils, wiring harness, and finally the fuel rail. The only thing that caused a little head scratching was the wire that goes to the AC compressor. But nothing special really.
The following day I took the injectors to be tested and cleaned if necessary. They all checked out, which was kind of disappointing because I hoped they might be the cause of my idle problem. The first column in the report below means leak test while pressurized, and the second one is the spray pattern.
All that was left was to unbolt the manifold itself, and the left brake booster vacuum line. It was a bit tough to get to but nothing too bad. The bolts were all easy to get to and gave in after spraying a little WD-40. You need to be very careful with the Allen bolts though as they strip easily.
In addition to the manifold bolts, you also need to remove the upper bolt of the right bank engine hoist bracket at the back of the engine. It’s a trivial detail but it almost made me shed a tear of joy to see how that bit was designed: On the left bank bracket, and that one only, there’s a slot that’s designed for reaching the bolt on the other side easily. You could reach it otherwise too, but it makes it a little easier. As an engineer, I found that a beautiful detail. After removing that bolt, the bracket bends just a little which makes it easier to wiggle the manifold out.
Speaking of the manifold, the WIS says something to the tune of “lift it to the side”, but I found that it came out by wiggling it up from the front. Once you get it past the power steering fluid reservoir, it comes right out.
After the manifold was out, the next step was to undo a couple of dozen bolts to get the valve covers out. I took them and the manifold to be glass bead blasted and powder coated, and I’m still waiting to get them back. Fingers crossed they’ll look nice.
The next step was to remove the flanges between the heads and the intake manifold. Nothing special there except some more unbolting, which was easy as this time I sprayed WD-40 the day before. As a result, the crankcase breather pipe on the bottom of the valley was exposed. To get to the knock sensors it needed to be removed, and I wanted to check it out anyway. It’s bolted to the head at the front and middle of the engine.
Once I got the breather pipe out, it seemed pretty clear what my idle problem was about. The wide plastic center part of the breather, the pressure damper, was cracked. And not by time or wear, but quite obviously because someone has been there before and forced it in place. I have no idea why, especially as all date stamped parts I’ve found down there seem to be originals, so it doesn’t seem like anyone has actually replaced anything before. Gaskets don’t have date stamps so I don’t know about them. In any case, the damper was leaking and it’s quite certainly a source of unmetered air and therefore the (or at least a) cause of my idle issue.
The bad news is that now I have to wait a couple of more weeks to get the replacement part. The pipe costs around 100-150 EUR depending on the seller. While at it, I also ordered the small coolant hose that connects the heads through the hoist brackets, and the hose that goes from the same place to the firewall (towards the heater core). And the O rings on the hoist brackets that act as pipe fittings.
Now that the breather was out, I was able to replace the knock sensors down in the valley. Nothing special there either. I had also decided to deal with the crankshaft position sensors while I had the access. The right bank sensor was readily accessible from above after the intake was off, but there’s no way you can reach the left one. It’s too tight between the firewall and head. However, after removing the upper firewall portion and the heater hose that goes from the back of the V to the firewall, the bolt is easily accessible with an extension.
The trick to removing and installing the sensor is to wiggle it by the cable through the back of the V valley with the plug connected. Before I figured that out I feared I couldn't do it at all, but in the end it was surprisingly easy. Careful with the cables with both the knock and crank sensors though - I’m told their insulation deteriorates and they’re unobtainium. I didn’t see any damage on mine though and the cables were flexible.
The last thing I did so far was to replace the two hoses between the tandem pump and power steering reservoir. Having done it, I think it would be possible to do even without removing the manifold, but it was certainly easier this way.
Here’s the list of parts I’ve ordered so far:
- Valve cover seals: A1200101430 & A1200101530
- Power steering reservoir hoses A1409975782 & A1409975682
- Throttle body gaskets, 2x A1041410780
- Knock sensors, 4x A0031538628
- Seals between intake manifold and intermediate flange, 12x A1041411080
- Gaskets between intermediate flange and heads, 2x A1201410280
- Plastic holders in rear corners of valve covers that hold the crankcase breather pipes that go to the throttle bodies, 2x A1200160338
- Crankcase breather pipe gasket A1200180180
- Coolant hose between hoist brackets in the rear of the V A1202030382
- Hoist bracket O rings, 2x A0129975148
- Heater hose from rear of V to firewall A1298300796
- Crankshaft position sensors, 2x A0031537228 or A0031537428 (interchangeable, not sure what the difference is)
- Bunch of vacuum bits and pieces as well as some mounting bits such as MAP bracket mounting buffers A6019880111 and air cleaner mounting buffers A1029880111 that were broken
At this point I’m about 7-8 hours into the job, excluding all the studying online and with Alldata/WIS, figuring out what parts I need and getting them, and of course taking the parts to be painted and injectors to be tested. I’m working in a public parking facility where I have a permanent spot, so the time includes setting up before and cleaning up afterwards. The trunk is my toolbox and storage…
To be continued when I get the valve covers and/or the remaining parts I’ve ordered. Below is a teaser of the color options I was considering. I went with RR41. The color chart is that of some Finnish industrial company so you probably won't find the exact same color pretty much anywhere. It's called metallic dark silver and has some metal flakes. I'm an OEM kind of guy, but I don't mind a little refresh here, especially as I couldn't find an exact match to the original colors.