Wednesday, December 09, 2015

New Wheels Day

After my recent move to Tennessee I'm finally getting back around to doing stuff with my cars. Since I never had to worry about winter weather in Tampa it occurred to me that I might not be able to drive on summer tires year-round anymore. If we get some nasty winter weather (I'm told it can happen here) I need to be able to get around reliably. So, I ordered up a set of Kumho PA31 all-season tires mounted on 15x7 Advanti Storm wheels from The Tire Rack.

I have to say I'm digging the black wheels on this car. They work well with the black hardtop. I'm thinking a small ducktail spoiler on the back might work well now. These wheels weigh only 10.4 pounds so the car feels great. I don't know how much grip to expect from these tires, so I'll be taking it a little easy until I get a feel for them.

Saturday, September 12, 2015

Assembling the Miata Engine Short Block - part 3 of a series

This the third post in a series. Part One, and Part Two came before this one. Here's part 4 which came after this one.
In this post I'll briefly go over the assembly of the engine short block. I'm not going to quote torque values here. Look those up for yourself. It's important you verify that yourself. I took the block, crank, rods and pistons to 3D Service in Tampa, Florida. I had them overbore the cylinders 0.5mm, resurface the block, clean it, install new freeze plugs, check and polish the crank, and check the rods. This all came to $500. I had bought a set of DNJ brand 2001-2005 pistons in 83.5mm (that's 0.5 bigger than stock to account for the overbore) from Rockauto because of the higher compression ratio (10:1) compared to my 1994's original 9:1 ratio. I supplied the pistons to the machine shop so they could properly clearance them when they did the overbore. Even at 10:1 compression this is still a non-interference engine.
So now it was time to assemble everything. I started with the rods and pistons. These are fairly easy to assemble. I was wishing for a better set of snap-ring pliers but I managed to get them together. Assembly is made easier by either getting the wrist pin cold, or making the piston hot. I think the hot method is better because the cold method resulted in condensation forming on the pin, which made it slightly wet. I used plenty of assembly lube and gently tapped the pin into place, and then snapped-in the snap rings. MAKE SURE YOU INSTALL BOTH SNAP RINGS! I almost left one out which would have cost me the engine.
Once all the pistons were assembled to the rods, I moved on to the rings.
The rings are clearly labeled as to which rings they are, and also to which way is up.
You have to space out the end-gaps so they don't line up. My shop manual spelled out exactly how to space them. This photo shows only the oil control rings assembled. Note that the spacer ring has an up-down direction, but the oil control rings don't. The first and second compression rings are not identical and also have an up and a down. Don't mess this up! I used a pair of ring pliers to get the compression rings in place. They're quite stiff so it would be hard to get them on with your fingers. The oil control rings are easy and you won't need the pliers for them.
Do not buy this tool to compress your rings, or if you did, deposit it directly in the trash. I deposited two of them in the trash before I learned my lesson.
Meanwhile, I installed the main bearing top halves and gently laid the crank in place, then torqued down the bearing caps (with the bearing halves installed, of course, and plenty of assembly lube). Don't forget the thrust washers on the number 4 journal. The crank spins freely in the block at this point.
This is the hardest part of the build - getting the pistons in the bores. The cheap ring compressors flat didn't work so I bought a better tool, which worked but was still really hard to use. This photo shows three pistons in place. Took me about an hour to get to this point. The first oil control ring likes to sneak out from under the compressor and hang up on the rim of the cylinder just as you are tapping the piston in. Like, 90 percent of the time. Note that there is a front and back to the pistons. These DNJ pistons have a round mark on the top indicating the front of the engine. There is a cut-out area of the skirt to clear the oil squirter in the block. If you install the piston backwards it will collide with the squirter.
This is the tool that actually works. Mind you, the oil control ring still hangs up 9 times out of 10, but it eventually works and you don't get your hands all sliced up and your block scratched. I got this one on Amazon and it's a GearWrench brand tool. It comes in a nice case and has a variety of rings for many different bore sizes. I'll probably never use it again, but I have it.
I found that if it kept hanging up on the rim of the cylinder if I reoriented the tool on the piston sometimes it would go in. You have to be careful not to mess up the spacing of your ring gaps while wrestling with this. I probably did. I gently tapped each piston into place with a wooden handle. Once the oil control rings get past the rim, the whole thing goes in easier. If you feel increased resistance, STOP. If you force it you will bend a ring and score the cylinder wall. Keep everything coated and lubricated with oil while doing this.
When you're tapping the pistons in, make sure to put some tape over the end of the rod bolts, so they won't scratch the crank journals. I fount it best to rotate the crank so each rod journal was at its lowest point before I installed the rod.
Finally I installed the rod bearing caps, again with plenty of assembly lube. With the pistons connected to the crank it doesn't spin quite as easily but you should still be able to move it by hand. If you can't, something is wrong.

Saturday, July 11, 2015

94 Miata - Engine Rebuild, Part 2

Since my last post I've removed the engine from the car and disassembled it. I was hoping to be able to simply hone the cylinders and put the engine back together with new rings and bearings, but I found there was too much wear for that. I didn't even make any measurements. There's obviously a lot of scuffing on the piston skirts and there are enough scratches on the crank journals that I figured I'd better have it polished and maybe even ground down one size if necessary. So off to the machine shop it will go this week. I'm taking them the block, rods, new pistons, and the crank from a spare 2002 engine I previously tore down. Here are a few pics of the pieces.
In this photo you can see quite a bit of scuffing on the piston skirt. The oil control rings on all these pistons did not appear to be stuck, so I believe my oil consumption issue was simply due to wear in the bores.  
This is one of the main crank bearings. It's probably the worst one but they all looked similar. It's not the worst I've seen, but you can tell this is an engine with 175,000 miles on it. It's worse than I expected it to be. This engine has always had synthetic oil in it, and although I've pushed the change intervals pretty long a few times, it's had regular oil changes. I chalk up the increased wear to several factors, though. 1) I had a very crappy cold air induction system for several years that didn't filter the intake air very well. It was an oiled foam filter and several times I found actual grit in the airbox. Most of the bearings showed deep scratches indicating large particles in the oil. This is usually due to ingested silicon grains. 2) I had a supercharger on this engine for about 10000 miles, and 3) this engine saw some track mileage where it was at very high rpm for extended periods of time.  
On the left is a rod from the '94 engine and on the right is a rod from the 2002 engine I previously tore down. I didn't weigh them but to me the 94 rod looks like it might weigh a little less. The webbing on the I-beam portion of the rod is definitely thicker on the 02 rod. Maybe they beefed them up in later years to compensate for the higher compression the NB engines run. At any rate, I decided to stick with the '94 rods for my rebuild. I'm sure they're still strong enough and I just thought the construction looked a little better. If I was going with forced induction I'd probably use the '02 rods.  
I bought some new pistons in 0.5mm oversize (83.5mm) because I figure it's safer to oversize rather than just hone this block, based on the amount of wear I'm seeing. The bores in the block look pretty good, but the amount of scuffing on the old pistons tells me there's gotta be some wear. So just to be safe we're going to overbore.  
This pic just shows the crank still assembled to the block. The main bearing caps are stamped with numbers 1 through 5 and there are cast arrows indicating the direction to the front. The numbers are hard to see but they are there. I elected not to use this crank and will instead use the one from the 2002 engine I took apart because that one looks brand new and this one shows some wear on the bearing journals and seal surfaces.  
Here's the bare block in all its glory. Not much to it when it really comes down to it. Part three of this series is here.

Tuesday, June 16, 2015

94 Miata - Engine Rebuild, Part 1

Going back about 3 years on this blog you'll find a long series of posts about how I went through my Miata and refreshed a bunch of stuff. Highlights of the project included installing a '99 cylinder head on my '94 motor and painting the entire car myself in my garage. What I didn't do back then was rebuild the bottom end of the engine. Since then it's been burning oil pretty rapidly and showing some rather poor compression when cold. So, I decided it's time to pull the engine again and do a complete rebuild on the bottom end.

I'm picking this project up sort of in the middle here, because I've already got the engine out and on a stand. When I last had the engine out in 2012, the cylinder bores looked very good, so I think I can get away with a simple hone and re-ring job, with new crank and rod bearings. I plan to use a Flex-Hone rotary brush type honing tool. These are inexpensive, can be done by hand with a drill, and provides a high-quality finish with the proper cross-hatch angle to ensure a good seal by the rings. I've torn down a spare 2002 engine block we had at the Gorilla Garage and I plan to use it to practice my honing technique. I also plan to use the pistons from that engine to take advantage of the 10:1 compression ratio enjoyed by the 2002 Miata engine. This will be a true budget-build, because if the block looks and measures ok, I'm going to get by without doing any machine work. We'll see if that pans out! The head only has maybe 35k miles on it, so I'm hoping to leave it alone at this time.

To sum up part 1 of this series, here are my goals for this project:

  • Rebuild engine bottom end
  • Inspect head and correct any issues (don't expect any)
  • Refresh suspension
  • Install soft top
  • Install Flyin' Miata frame-rail braces
  • Detail engine compartment
  • Repaint hardtop
This list is subject to change and I probably won't get to all of it before I put the car back into service as a daily driver, but it's all the stuff I'd like to get done, so I can drive this car for another three years. Stay tuned for part 2 of the series as I get into the engine over the next few weeks.

Monday, January 26, 2015

E46 M3 Cooling System Refresh

I've owned this 2004 BMW M3 for well over five years now. It had 82,000 miles on it when I bought it in 2009 and at the time of this writing has just over 128,000 on it. I got it completely caught up on maintenance when I first got it, but other than regular periodic maintenance, it's needed very little else in that time. The only unplanned repair it has gone down for was a seized front brake caliper which I replaced. At this mileage, though, I know I've been driving on borrowed time for a while. The E46 does not suffer from the same cooling system weaknesses that the E36 did, but it's still a very critical system on the car and the consequences for poor maintenance are dire. So I decided it was time to completely go through the cooling system and renew everything I touch.

As usual with my blog, this is not a how-to. It's a you-can. There are plenty of forum posts and blog entries elsewhere that will tell you everything you need to know to complete this maintenance.

I started with an order of parts from ECS Tuning.

  • Genuine BMW Remanufactured Water pump #11517838118
  • Genuine BMW Radiator #17102228941
  • Genuine BMW Thermostat #11531318274
  • Water pump gasket #11517831099
  • Thermostat O-ring #11531318402
  • Water pump O-ring #11537830709 (qty 2)
  • Coolant pipe O-rings #11537830712 (qty 2)
This order with shipping came to $710.

Thankfully the water pump for the M3 has come down a LOT in price since a few years ago. It used to be over $500. This one was $300 and I've seen a few other cheaper options as well. Shop around. Make sure you get a pump with a polymer impeller. It will last forever. The front bearing of the pump will wear out, not the impeller. If you get a metal impeller I can't say the same will be true. Here's a pic of my removed water pump (right). The impeller is perfect. This pump was not leaking but the bearing is pretty loose. This also shows how well the BMW coolant protects the engine from corrosion. There simply is none.

To start I removed the lower engine shield, fan with clutch, fan shroud, intake filter housing, hoses, belts, and finally the radiator. The lower radiator hose was impossible to get loose from the rad so I left it in place and removed both through the bottom of the car. You have to move the oil cooler out of the way but you can leave it attached. Support it with something so it's not hanging by the oil hoses.

When removing the thermostat housing there's a coolant pipe that runs between the housing and the bigger pipe that runs to the back of the engine. It's about 2 inches long and machined from aluminum. It is sealed with O-rings (#11537830709) on both ends. Mine pulled free from the engine end, not the thermostat housing end, and thus the whole housing was too big to remove from the space it occupies. I had to work for quite a few minutes to get the pipe loose from the housing side so I could remove it. Most write-ups I've seen don't tell you to remove that pipe at all, but there is an o-ring on the engine end that you should replace as well, so it's just as well that it came out that way.

Once the thermostat housing and thermostat are out of the way, you can unbolt the water pump. A firm pull disengages the pipes on the back side and it easily comes out.

At this point I assessed where I was and decided I needed a few more parts to do a more thorough job. Again from ECS, I ordered:

  • Radiator Fan Clutch #11527831619
  • Aux fan switch O-ring #13621433077S
  • Expanding rivet (qty 4) #17111712963
  • Heater hose #64216902679
  • Heater hose #64216902680
  • Hose #64216902678
  • Air filter #13721730946
  • Cooling fan blade #11521712058
This order came to about $160.

Replacing the heater hoses requires removal of the intake manifold. Due to the M3's six individual throttle body design, there are six individual hose clamps to remove. The factory clamps are Oetiker-style clamps that require a special pair of pliers to remove without destroying them. The Lisle 30500 CV Boot Pliers will do the trick. Using the pliers I was able to remove the clamps without damaging them. The intake manifold, having never been removed before, was very hard to dislodge from the throttle bodies. The throttle body boots are pliable rubber, but were VERY stuck. Rather than risk breaking something, I opted to carefully cut the boots with a knife and pry them loose a bit. After unclipping all of the hoses and wires that run along and around the manifold, it finally came out. This means I had to order new throttle body boots, part #11617830265. About 17 bucks a piece. I also ordered new clamps for the manifold side of the boots (#11617830306). While the throttle-side clamps can be reused, the manifold-side clamps are one-time only. They're a bit over $3 each, and I had to buy a tool to crimp them, the Lisle 30800 CV Boot Clamp which was about $25 at Amazon (photo above). You can use traditional hose clamps, but these are simple and look factory.

Once you have the intake manifold off it's easy to replace the coolant hoses that feed the heater core. There's one other hose that doesn't connect to the core, but rather connects the heater valve to the back of the coolant pipe alongside the cylinder head. I found it rather hard to find the part numbers for these hoses. Even ECS's website doesn't tell whether they fit the E46 M3 or not. They do, and the correct part numbers are in my list above. The photo here shows them fairly well. For what it's worth, my original hoses were still nice and soft, and looked pretty much like new. I think I could have easily gone another 50k miles on them.

Once I had the hoses replaced, everything went back together quite quickly. Access to the cooling system on the M3 is very good and doesn't require many contortions (except for those three hoses under the intake manifold). While I was in there, I also replaced the main serpentine belt tensioner spring and pulley. I had bought them a long time ago so they are not listed in the parts list above. The bolts that hold the water pump to the block should be tightened to 7 lb-ft of torque. That is NOT VERY MUCH. I don't even have a torque wrench that will read that low. I used a 1/4-inch ratchet and very gently torqued these bolts down. The bolts that hold the pulley to the water pump snout are also torqued to 7 lb-ft. Be careful!