Playing Doctor Nov 14, 2007
With a number of weird symptoms popping up regularly, it was time to spend a day playing doctor with our Spec E30. The rear brakes are seizing up symmetrically, the car runs rich nearly all the time, and we’re still down on power. Plus the fuel pump started making weird noises at the end of the NASA Championship race and power delivery went all wonky late in that same race.
We loaded the Spec E30 on the trailer and headed off to the Ocala Gran Prix track where we do much of our car testing. While we could have done most of the diagnostics in the garage, our rear brake issues only seem to materialize when the brake system is hot, so the track was necessary. Rennie Bryant of Redline BMW Performance came along with his years of BMW experience to help out.
Before we hit the track we wanted to try to figure out why the car is running so rich. We suspected the fuel pressure regulator, so we made a T-fitting out of some brass hardware in order to hook up a fuel pressure gauge and see what kind of pressure the fuel system was getting.
After we fired the car, the needle immediately jumped up to 90 psi. That’s more than double what it should have been reading at idle. Okay, so obviously we’ve got way too much fuel pressure. We swapped out the fuel pressure regulator, but that did nothing to fix the problem.
Rennie remembered a former customer who had a clogged return line in their E30, and he suspected that might be the case here. We unhooked the fuel return line and ran it into a large glass bottle so we could get a reading without the backed-up fuel return line sending the pressure to the clouds. We saw about 40 psi on the gauge with an unhindered fuel return route. After a few seconds, we also had the start of a nice Molotov Cocktail, so we killed the engine. The fuel return line carries a LOT of fuel in a short period of time, so make sure you’ve got a big enough container whenever you unplug it for testing purposes.
After unscrewing the gas cap, we used an air compressor to force air through the return line to see if we could blow the clog out. We were rewarded with air and some gas bubbling out of the tank, but the pressure still stuck at 90 psi after we hooked everything back up. The problem seemed to be somewhere in the lines of the tank itself, so we’ll have to remove and either clean or replace the entire fuel tank–Oh, joy. At least we’ve got a likely culprit, and a clogged return line would explain why the fuel pump is straining and the car is running rich as a pig. Fixing it might even free up some of our missing horsepower.
With the car put back together and running, we tried to get our brakes to seize up as they have been doing so Rennie could experience it and help figure out the problem. Naturally, the car drove just fine, with no indication of lockup; why would it want to provide tangible evidence of its malfunction with a certified mechanic around to help fix it? That would be too easy.
We tore into the rear calipers anyway to see if the culprit was mechanical. Although there was lots of nasty goo behind the caliper piston, they did seem to be moving as the factory intended. We bled the system and headed back out. A number of abusive ABS-engaging laps later we came back in, still lacking evidence of the problem. We chatted with Rennie about Murphy’s Law, sitting with the car at idle, and when we’d given up hope and lifted the clutch to take the car back to the trailer, the tail end sunk down as if the parking brake were on. Hooray! We ran for the tools and went right for the ABS unit, which Rennie suspected was to blame.
Sure enough, as soon as the hard line going from the ABS unit to the rear brake was disconnected, the pressure was relieved and the BMW rolled freely.
Hopefully, replacing the ABS unit and the gas tank will leave us with a much happier BMW.
Fuel Tank Frenzy Nov 20, 2007
If you remember from our recent Ocala test, our car’s perpetual rich-run condition seemed to be related to a clogged or restricted fuel return line. We were seeing 90 psi of fuel pressure at idle, as the fuel coming from the pump had nowhere to go once it was done feeding the fuel rail. It wasn’t the fault of the fuel pressure regulator (we replaced that), and the line was found to be clear as far back as the entry point to the fuel tank. That meant that the line was messed up somewhere inside the fuel tank. Unfortunately, that meant it was time to take the tank out.
Our two options were to remove our stock fuel tank and get it cleaned or to buy a new tank. Cleaning the OEM tank seemed to be the cheapest way to go, but our tank also had some dents in the bottom, and without cutting it open there was no way to tell if the line was clogged with goo or physically crimped. Cleaning might not have fixed anything. Most of the replacement tanks we found online were going for more than $300, with OEMs listed closer to $500.
That’s when eBay came to the rescue. It took a bit of digging, since searches like “BMW 325 fuel tank” didn’t work, but when we got specific and searched for “BMW 325is gas tank” a shop called The Radiator Connection popped up. They had both the early BM1A and later BM1B tanks listed, the former for $100 and the latter for $130 (plus about $40 shipping in each case). Naturally we were skeptical of the low price, but the seller had more than 17,000 transactions and a 100 percent positive rating, so we figured it was worth the gamble.
A miss-read on our part led us to first order a BM1A tank, which is for the earliest 325is models. We actually needed a BM1B, so we returned the earlier model tank after taking some pictures for posterity. In both cases we had tracking numbers for the packages within 30 minutes of placing the Buy It Now bid on eBay. We added our own positive ranking to the seller’s 100 percent streak.
The eBay tank was a dimensional match for the OEM one, although it lacked the small plug at the bottom of the passenger’s side that can be used to drain the tank. For what it’s worth, our OEM tank’s plug was completely frozen in place anyway. We drained most of the fuel by MacGyvering up an extra long hose off the fuel return nipple on the fuel pressure regulator running it into the fuel tank of one of our other cars. (If you do attempt this, refrain from smoking, please).
Replacing a gas tank is a messy chore, as it requires the removal of the exhaust as well as the driveshaft. Also, get used to smelling like gasoline, as it’s nigh impossible to completely prevent spills as you disconnect the many lines carrying fuel hither and thither. Label lines and hoses as you go, and take the opportunity to replace any worn looking hoses with new replacements. Just make sure that you use fuel injection hose for the pressurized lines; we bought two feet of the stuff (about $10 at Pep Boys) and that was plenty for the three or four hoses we replaced. Since the OEM hose clamps are of the cheap single-use variety, buy a bunch of stainless screw-type hose clamps as well and replace as you go.
BMW Brake Bonanza Dec 19, 2007
With our fuel delivery issue sorted out, the next big ugly box on our to-do list was the brakes. Specifically, we needed to eliminate the BMW’s tendency to apply increasingly severe rear brake line pressure to both rear wheels all by itself until the car could barely accelerate, even in first gear.
After experiencing the problem in competition and re-creating it under test conditions, we had a pretty good idea of what was going wrong. The rear brake line (it’s a single hydraulic line until it splits in two near the rear differential) was for some reason unable to release pressure, causing the rear pads to drag on the rotors. This manifested itself physically by making it feel like the parking brake was partly engaged, as the rear of the car would dip under acceleration from a stop and more gas than usually was necessary to get underway.
If we tried to drive through the problem, the pads would continue to drag, heating everything up. As the calipers and lines heated up, the fluid inside them expanded, increasing the pressure. When things were at their worst, the car would barely move. With enough momentum we could drive through the problem to a certain extent, but this had pretty catastrophic consequences for the poor rear brake pads as they were pushed well beyond their temperature limits.
Finding the source of the problem was the real trick. Essentially, it could be any one of the four major components that make up the brake system. Originally there could have been five sources, but we already removed our rear brake line pressure regulator at the NASA Championships, so all that’s left of our brake system is the master cylinder, the lines themselves, the ABS unit and the rear brake calipers.
Our rear brake calipers were gross, but we’d given them a field refurbishing at the NASA Championships and the pins slid and the piston compressed as they should. Also, the problem seemed symmetrical, so we felt it was unlikely that the rear calipers were simultaneously responsible. Still, our calipers were rusty and gross, so we got a set of refurbished calipers from Redline BMW for $65 each. One variable down.
Next we pondered the brake lines themselves. We found a dinged-in section of line when we were replacing our fuel tank. In our testing we determined that disconnecting the brake line fitting at the ABS pump relieved the pressure on the rear brakes and allowed the car to roll, so logic dictates that the problem was at the ABS pump or upstream of that, but we still didn’t like the idea of a crimped line, even if it was allowing fluid to flow freely. We picked up some replacement steel line at AutoZone. That’s another variable checked off.
Next on our potential list of culprits is the ABS unit. The first time we experienced the problem was at Summit Point just after some particularly heavy braking going into Turn 5. We were very likely engaging the ABS, and when we went to get back on the gas the tail end was locked up so hard we barely made it back into the pits at full throttle in second gear.
The factory service manual warns against tinkering with the ABS unit, but it didn’t really say anything about replacing it. Rennie at the aforementioned Redline BMW had an old 325i pump in his possession, so we figured making the swap was worth the trouble. There’s no guarantee that the new used pump is any better than our used used pump, but we’ll cross our fingers as this is the component we suspect the most.
The last potential culprit is the brake master cylinder. This little doodad goes for about $150 at the online retailers, so we were going to skip it on this first round. All that changed when we saw an engineless BMW 318is at the local junkyard with a fairly new looking Girling master cylinder. we ran home, grabbed our flare wrenches and sockets, and about 15 minutes and $6 later we had a replacement master cylinder. It even cleaned up prettier than our stock unit.
Short of replacing all the lines and buying a brand-new ABS unit, we’ve attacked this problem on all fronts with this recent bout of work. We though about doing things part-by-part in an effort to pin down the exact culprit, but bleeding brakes more than once seems like a hassle when you’re dealing with $6 used parts. Frankly, we don’t care if it was the ABS pump or the master cylinder as long as the new parts have fixed the problem.
Spec E30 Post-Repair Shakedown Jan 21, 2008
A completely reworked brake system and a new fuel tank leave us with what should be a fully operational BMW Spec E30 race car. The only way to find out for sure, however, is to go drive the thing.
While we were going through the list of things we’ve done to the car since the last in-magazine update (look for the next installment in the April 2008 issue), we recalled a few other fixes that have taken place.
First up was the replacement of the completely fried engine mounts with some more rigid Vorshlag Motorsports units. These aluminum and nylon mounts cost $159 for a set of two from Vorshlag.com and installed easily. Having a friend handy to work the jack or engine hoist while you tighten up the four bolts helps, though.
Another snag we had almost forgotten about was the discovery that one of our Bilstein dampers had pulled completely off its lower mount bushing while on the trailer. We’ve been using chains to keep the back end of the car from misbehaving while in tow, and the slight inward pull was enough to wiggle the damper tube free. A trip to the hardware store gave us a pair of big washers that should fix the problem.
We’re happy to report that the long list of repairs seems to have done the trick. The car performed better than ever at our Ocala test track. After a lot of brake bleeding (with lots of help from Margie in the pedal pumping department) we’ve got a firm brake pedal and no signs of rear brake drag. The engine even ran well, and it sounded wicked with a cutoff exhaust.
Soon we’ll be bedding in a fresh set of Carbotech brake pads and bolting up the new, just-released spec exhaust system. We’re looking forward to doing more racing than troubleshooting in 2008.
Exhausting Work Feb 21, 2008
There’s been a lot of buzz going on at the Spec E30 forums for the past few months about a change in the exhaust rules.
Like any rule change that involves a spec part, the announcement of a mandatory spec exhaust system caught some racers at the worst possible time; imagine torquing down the last bolt on your fancy new exhaust and then finding out it’s been rendered obsolete by the rules. For others, the announcement brought relief; nobody will be able to spend huge money on a fancy system to gain a slight competitive advantage over their more thrifty neighbors.
We got the impression that the series organizers wished they’d written a spec exhaust into the rules from day one. Until we get a spec time machine, however, that’s not going to happen. The moral of the story is that starting in June, all NASA Spec E30s will be on the same exhaust. The rule is included at the bottom of this post.
Fortunately for us, our BMW 325is was still on its stock exhaust, and we were eager to get rid of it. In fact, knowing that we’d have to make the change to a new exhaust anyway, we chopped that sucker in half to facilitate the fuel tank change while still keeping the car drivable.
The new system costs $175 plus shipping from the mandatory supplier, Paul Poore. Expect to spend about $200 after shipping. It’s not a pretty exhaust by today’s chrome-tastic standards, but the unit is mandrel bent and made in the U.S.A. Kudos to the NASA organizers for keeping the price very reasonable.
We’ve heard an exhaust leak in our BMW since we bought it, so before mounting up the new part, we decided to take the downpipe out and give it a good look. We were hoping that we’d just need to replace the triangular gaskets that seal the downpipe flanges to the exhaust manifolds, but once we got the downpipe on the ground we saw that the situation was dire.
The gaskets were toast, sure, but one of the flanges was completely broken off the tube. Plus, there was a crack on the aft downpipe where it mates to its accordion section. We’re in a holding pattern on the install while we source a replacement downpipe.
We also stepped on the scale to weigh each system. Our OEM exhaust (with a bypass already in place of the catalytic converter) weighed 53.4 pounds. The spec system weighs just 21.8 pounds, a 31.6-pound savings. We may need to add some ballast after all.
We’ll post the installation photos once we source a new downpipe.