Engine Swap Blues

[brendanode]

I'm at a pretty tricky spot with my '89 325i I bought back in January that I was planning to fix up as a fun project

After having a lot of work done to it by a local mechanic (Timing belt, radiator, oil pan, suspension, heater core, etc.) the car was still stalling with a rough idle. I replaced things I could think contributing (rebuilding MAF, TPS, crankshaft sensor) and checked for vacuum leaks but still no luck. The last mechanic I had it at suggested I take it to an engine specialist who basically told me the motor was kaput, probably a bent out rod. I knew this was a possibility as I got a stellar deal on it from the previous owner who said at some point the timing belt had broken, so my best guess is that it wasn't put back together properly.

I have a new top on order, I've fixed up the interior and the exterior is in pretty good shape so I feel committed and honestly I want to be. I love everything about the car - it's exactly the style and color combo I wanted and even with it stalling out it's a ton of fun to enjoy and drive.

Basically my best option is to replace the engine. The local engine specialist found one with 115k on it (there's 70k on the chassis) for about $3k shipped plus whatever it costs to install. The engine would come with a 3 month warranty, but obviously there's no guarantee on the labor. The shop has great reviews and specializes in foreign cars; the mechanic has done E30 swaps before.

Is this my best option? I've been calling around and it seems like no garage has the capacity or willingness to take on the work. I love the car stock and I'm not really interested in putting a bigger or better motor in it. I'm in the DC area and relying on the mechanic for finding the ending options as I come up short myself looking online. Any recommendations or words of advice would be appreciated

[Pro1914]

Personally, 3k for an M20 is ridiculous, especially for 115K miles considering you can find a whole car for that much, part it out, and profit way more, but maybe it's just where I'm located. Regardless, if I were you, I'd either try and find a local part out, check Facebook marketplace, or craigslist in your area.

As for installing the engine, the M20 is a really easy motor to pull, and there are so many writeups on how to do it yourself if you feel inclined to do so, but if not, be prepared to pay top dollar to get it put in. I've seen people spend upwards of 5K. A shop's rate usually sits around 100$/hr and I don't see this taking less than 10 hours to do. I believe the average someone is quoted is around 30 hours.

Lastly, are you 100% certain that it is a bent rod? Have you tried getting a second opinion? I'd just hate to see someone have to spend so much money when it could be something completely different that could just be a simple fix, but then again, I'm not an engine specialist, just an enthusiast.

[brendanode]

It's been to three different mechanics now who have all said pretty much the same thing - they think it's a rod knock. That coupled with all the other parts I replaced, plus the compression testing the last mechanic did, plus the previous owner saying that the timing belt had failed previously... it adds up.

I found the same engine the guy was talking about on car-part and it's actually $1500 (plus core charge & shipping) and when I asked if it was the same one he told me about he said yes; $3k was his all in price plus markup. He also quoted me about $1500 for the work, which based on what you said and calling around other places seems high, too. Maybe it's normal to mark up things up but it definitely left a bad taste in my mouth. Nearly $1k feels nuts... Especially when another mechanic I spoke to said "yeah order the engine and I'll install it for $900"

Maybe I should take my time and sit on it and hunt around for a lower mileage engine and a more reasonable mechanic, I just know they don't come up that often. The guy with the engine in question told me he had others interested and it includes a 3 month warranty

There's no easy answer here, I'm afraid

[tyeler18]

Is the car making noise? A rod knock wont make a car stall, what exactly is it doing? Does it drive OK? Sounds like it has a bent valve which would make for a rough idle/stall coming to a stop which would also show low compression in the effected cylinder. What were the compression numbers? A head swap rebuild is a lot cheaper than an engine replacement. If it's not making noise and just stalling I'd like to know what let them to believe the engine is causing it to stall, could be a number of electrical components that probably won't get changed with an engine swap and may leave you with the same issue and a giant bill.

[e30davie]

Need to absolutely confirm the status of the old engine. The oil pan comes off relatively easily to check the rod bearings. but if its as stuffed as you make it sound then pulling the entire engine out is proabbly simliar amount of time. then you can put it on a stand.

Busted valves from a arent a big deal if the head isn't damaged. but its a head off job, and a ~$800 trip to the machinist with another few hundred for gaskets. But it will be brand new when you get it back. unlike your $3k option which sounds like another 30yr old mystery engine.

Unless you start doing some DIY on the engine you are in for a world of pain from regular mechanics. if you dont want to DIY you'll need to search out an old bmw specialist and be prepared to pay...

[brendanode]

Yes, the car is making noise when revved somewhat hard. It sounds like a rattle deep in the engine. When it comes to a stop it seemingly runs like it's running out of gas. I'm getting another call with the mechanic tomorrow so there's some good stuff here of specific things I can ask him (Compression numbers, electrical check, rod bearings. etc.).

I'm really out of my element with engine stuff so I appreciate the help, but what I hear from my mechanic(s) is it's a rod knock and as far as I'm understanding that's something that can only be addressed by a rebuild or replace. Is that correct? If it's a connecting rod hitting would you really be able to bore out the cylinder to solve the problem?

[zwill23]

M20 is a noisy engine, you should post a video of the knock you're hearing. If you want an easy confirmation that the engine is toast with minimal mechanical work, change your oil and send a sample to Black Stone Labs. They'll give you a full diagnosis of what's in your oil including bearing material that would be aplenty if you have rod nock.

[jbontke]

I think the going rate for mechanical work is about $100 per hour and up. Depending on how long a mechanic says it will take wo swap the engine, you could easily see $1,000 as the labor cost. Also there are many "while you are in there" parts your mechanic should discuss with you (Clutch, pilot bearing, throw-out bearing, rear main seal, oil pan seal, etc). It's not cheap to replace an engine. I think you could find a better deal on an engine on the east coast. I used to live in Raleigh, e30 parts turned up there consistently. If you are patient and watch, you can find a good m20b25 for $500.

I am assuming that you bought the car to fix a little here an there, but an engine swap is more than you want to attempt. If you have a few wrench savvy gearheads, get some help and swap the engine (friends are motivating as well). You will get lots of help here and on the FB group as well. Saving $1000 in labor is worth it.

[Reichart12]

Just for reference I had a indie shop in Maryland swap a M20 for me for $1300. I was out of state and needed the car fixed in a timeline I couldn't do on a short visit. I provided an engine that was confirmed good for $1200. That was more than was needed since it was engine, trans, subframe, ecu, accessories... Sold off some of those parts later on so just an engine I would expect that $500 range that was mentioned before. I have done a M20 swap before and saving the money would be ideal if you have the space and mild wrenching skills.

[McGyver]

Damn dude, it sounds like you're getting a little overwhelmed with all of it. There's no way to diagnose what's happening without being there, but maybe this will help a bit. Google some of this stuff to learn more.

I feel like being charged $3000 for an unknown motor is a bit steep. I would expect a known good motor from a running car with compression numbers to be ~$500-$750 on CL or facebook, but dismantlers are expensive because they have bills to pay. The extra $1500 your mechanic is charging is just in case something goes wrong and he has to do the job a second time on his warranty. It may make more sense if he's resealing the whole engine, but its still pretty pricy. At the end of the day, you have no idea about the condition of the replacement engine, which likely has some of its own problems.

The biggest issue I see is that you really don't know what the problem is and you're being told to just throw parts at it hoping for it to get fixed. The first step is to diagnose the actual problem, then decide how you want to deal with it. The whole issue could be as simple as a vacuum leak due to a loose hose clamp or missing o-ring. Or you could have worn out connecting rod bearings and need a rebuild.

I suggest taking the car to a shop that knows and works on e30s, Im sure someone can help you find a good place around DC. Otherwise, Guten Parts in NJ and Bimmer Rescue in Richmond, VA have good reputations.

Are you able/willing to work on the car yourself? If you are, $3000 will get you pretty far for rebuilding the engine. At that point, you could have a freshly built 2.7i stroker and make something close to 180whp versus your stock 160bhp on a "new" engine.

----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Valve Train Noise - M20 engines are noisy, like a sewing machine. This is because the rockers are riding directly on the cam shaft. This means there must be a slight gap, which results in the ticking. More modern engines use hydraulic lifters, which avoids the ticking.

It's essential to perform a valve adjustment every 20k-30k miles. The reduces the noise and makes sure the valves are opening/closing correctly.

Broken Timing Belt - This keeps the crank and cam shafts in alignment. The crank is connected to the pistons and the cam is connected to the valves. Since this is an interference engine, a broken timing belt can cause a piston or two to collide with a valve or two. This generally destroys a combination of the top of the piston (car won't run), damages the top of the piston (car still runs), breaks a rocker arm (car won't run), and/or bends a valve (car runs like shit). The only rods in our engine are the connecting rods on the piston, I suppose these could theoretically bend, but its more likely for the valve or rocker to break first.

Replacing a bent valve requires the head to be removed, replacing a broken rocker can be done with the head on the car, but the head should be pulled to inspect the pistons and leak check the valves.

You can do a combination of a compression test and a leak-down test to figure out if you have a problem. Compression will show if your engine is making compression and if it's uniform across all cylinders. Leak-down will help you to understand where air is leaking (rings, valves, head gasket, etc.)

Rod Knock - This is when the bearings between the big end of the connecting rod and the crank shaft are worn, allowing the rod to knock on the crank shaft. This will make a noise that is always present and increases with RPM. This has nothing to do with compression. If your rod is hitting the cylinder wall, you've got much bigger problems, like the engine isn't running.

You would need to remove the oil pan to inspect the bearings. You could replace any bad bearings without removing or tearing apart the engine, assuming you are able to correctly size the replacement. The correct fix is to do a rebuild.

Piston Slap - This is when a combination of your piston skirts and/or cylinder walls wearing, allowing the piston skirt to slap the cylinder. Unless its really bad, you won't hear it at idle and it won't affect idle. You should only really hear it at high rpm. Unless it's insanely bad, this won't affect running at idle.

The only way to check is to disassemble the engine and measure things. This would be fixed by a combination or replacing the pistons and possibly boring the cylinder to the next oversize (84mm --> 84.25mm).

[TobyB]

Compression and leakdown tests are complementary, and can tell you the state of the head and the ring seal.

You'd expect to see 6 pressure (psi) numbers (hopefully 3 digit) for compression, and 6 percentages (hopefully single digit) for leakdown.

Oil pressure is one 2 digit number- ideally over 20 at idle, 55 or so at speed.

'Rod knock' is an isolated thing, related only (maybe) to low oil pressure.

So yeah, that's a summary of what McG said!

As to replacing the entire engine with a used one, sure- paying for labor is hard, especially
when there are lots of little things that would benefit from a good fixin'.

But then, the old car hobby is either quite expensive or has a significant element of DIY.
Or both.

t
as the old cars get more complicated, the old car owners have to get more sophisticated.

[McGyver]

any updates brendanode ?

[brendanode]

Thanks for all your responses; I really appreciate them. Here's the update:

Guy I took it to (the one that wanted $3k for an engine) said it was getting bad compression after testing. Again, the original owner said the engine was put back together after a timing belt broke so I believe it just wasn't done fully or properly. I didn't like the way he was trying to do business by upcharging me for an engine when I found the same one online. I ended up taking it to another garage in town who works on imports. The guy raced an E30 locally for years and has some enthusiasts working in his garage so I have a good feeling about him being able to do the work. Problem is he's booked for a month so he can't do a full diagnosis, but he gave a listen to the rattle and said it was probably a rod knock. Again, after having it at three different mechanics who said the same thing and given the history and other parts I replaced trying to solve the issues I'm confident that's the problem.

I found an engine on Car-Part. Admittedly I maybe jumped the gun a bit but there really weren't a ton of choices. It was $1600 shipped from California across the country and has 98k miles on it - the guy said it was in good shape, tested, and came off a rear ended '87. He offered a 90 day warranty minus labor. The mechanic quoted me about $1500 all in for the work and thankfully there's pretty much already new parts on everything so there's no problems there. Hopefully I'll get a bit of money back from the old engine - had a mechanic I called for a quote ask me if he could buy the head from the old one already.

It's not the outcome I wanted but I'm in over my head when it comes to engine internals. To complicate things I've moved and no longer have access to a garage so it's staying with my family at the moment. I've done a lot of calling around and while this will suck financially it's reasonable given the problem and the fact that I love the car.

[rturbo 930]

Why not just rebuild the bottom end?