524TD Cracked head

[JakubKecskes]

Hi, half a year back i purchased a 524td E28, it was running ok, i adjusted the valve clearance and did some basic maintenance. It seemed to not have any engine faults, it only consumed some coolant over a while, i needed to top it off once in like 2-4 weeks with half a liter or so. Yesterday it was a little bit different, all of a sudden there was no heating in the interior and white smoke came from the exhaust. It even pressurised the cooling system a bit with what it seemed exhaust fumes. So i pulled it apart(the head off the block). before i dissasembled it, i did run a compression test on every cylinder.
#1-400psi
#2-340psi
#3-370psi
#4-370psi -this cylinder spewed water air mixture trough the glow plug hole when we cranked it the first time during no1 test. (scared the hell out of my friend in the engine bay)
#5-370psi
#6-380psi

Are these pressures allright or is it outside of tolerance? how much should a fully rebuilt engine have, and what number is a borderline value for a complete engine ovehraul?

So, as i said before, i did dissasemle the engine, and I will post hi-res pictures of each chamber of the head with the number of the cylinder in the photos






along with the mating surfaces in detail



Gasket

and the engine block photos.







There is a lot of cracks visible on the cylinder head between the valves.

My questions are:
-based on the mating surface of the cylinders, chambers, gasket photo etc, what might caused the failure? (my bet is the previous owner overheated it?)

-are those cracks on the head serious damage? or is it safe to just replace head gasket and put it back together.(for now, a complete resotration and rebuild of the entire car is planned, but for the next year)
-what is and if there is a proper way to test if there are any leaks through the craks in the heads?
-are the compression test results good or is it low compression?
-can the cracks be actually properly repaired?(will welded spots crack again or will they last?)

lastly if anyone would know, why these cracks occur as it is apparently a common issue, I would be very grateful for such info. Is it material quality issue, faulty manufacturing of the heads or just overheating due to bad design, or if it just,,you know, happens in the 40 years of the life of a machine.

Thank you guys for reading my post.

[Galahad]

I'm pretty sure the cracking is because the engines tend to overheat easily - just not a great design on BMW's first diesel.

It sounds like in your case the head gasket failed around cylinder 4 from overheating.

The compression ratio is 22:1, 22*14.7psi (atmospheric pressure) is ~320psi, so I'd assume you're good. I don't know what the spec is.

I see cracks between the intake valve and the swirl chamber cap on cylinders 3, 5, and 6. Based on the soot pattern it doesn't look like gasses are flowing through them, so I'd say you are fine at least temporarily - I could be wrong tho. I don't know about welding.

The lines between the valves appear to be from manufacturing since they're the same on every cylinder and look much neater than the other cracks.

[ecbimmers]

You have a head gasket failure. The old composite gaskets seal really well until they get old and start to break down. The pitting on the cyl 4 combustion chamber is corroded aluminum and tells you that there was water in the cylinder and the engine sat unused for some time. Also the details of coolant useage you mentioned indicate that the gasket was already leaking coolant from a water jacket to the cylinder and your last 6 months of running it and heat cycling, the leak finally worsened and was taking enough coolant in to create the white smoke. You should be good to go with a new gasket, but be sure to get a straight edge on the head to check for warpage.
Speaking of the head, onto the cracks...
Every single one of these heads I've seen has the fine cracks spanning between the valves. I know the guy who was a BMW North America instructor who taught the classes(for BMW dealer technicians) back in the late 80s and he told me not to worry about the cracks between the valves as long as they remain hairline. I have a junk head with 2 very pitted combustion chambers and those cracks have opened up enough to stick a thick flathead screwdriver in the them. The real check on these center cracks is to pull the valves and inspect the intake ports after a good cleaning. If the cracks are deep enough, you'll see them leading up into the intake port from the valve seat. Those cracks look acceptable, but the other cracks are concerning. The cracks spanning from the valve seat to the precombustion cup is not good since they too run under the steel valve seat. Opening of these cracks can loosen the tolerance for the valve seat and these are usually indicators of an overheating at some point.
Finally the 3rd set of cracks are in the precombustion chamber cups(precup, swirl chamber cup, etc). These aren't desirable(not that any cracks are), but unless you can source new cups or have a machine shop make some for you, you just have to run them. There is the possiblilty of a cup cracking all the way through and dropping a piece, but I think it's highly unlikely, especially if you are running factory boost and fuel settings. The cups are most likely made of Inconel(like other most diesel precups out there) or possibly a high grade of stainless steel. I'd bet they're Inconel though since nickel based alloys have a high heat resistance and would be better suites inside an engine than stainless. The issue with these super hard metals are that they are also brittle and can only take so many heat cycles and will definitely crack if overheated(while softer metals will usually deform before cracking depending on their application/location to heat sources).
Here in the US, it's getting difficult to find decent used cylinder heads that aren't cracked or pitted from sitting with water/moisture in cylinders. There were a lot more of these sold in Europe so maybe better luck finding a decent head in that region. I did just see from a brief google search that some company was selling a brand new head for $1900 USD, but I'm not sure if it was legitimate or what. BMWs mircofiche doesn't even show that precups were an original replaceable part so I'd imagine you had to order a complete head back then if someone overheated one of these. The cracking that we see today was probably minimal 20-30 years ago. Age, sitting without running for long periods, heat cycling, and turning up the fuel/boost has really caught up with these old diesels. They're neat old machines and a bummer that there isn't more support for them, but that's the way it goes with less popular models.
Back to your project-You would probably be fine to run the head you have under factory fuel and boost settings along with a healthy cooling system. I'd clean everything up real well and put it back together with a fresh head gasket, timing belt, water pump, and thermostat.

[gadget73]

cracks from pre chamber to valve are what i've heard of multiple times on these. Apparently they can be TIG welded but I don't know if welding cast aluminum might create more problems than it solves.

I'd be inclined to clean everything up and replace the head gasket after verifying the deck and head are flat. Short of finding a good head I don't really know what other practical options exist here.

Might want to verify your injectors are spraying properly. Issues there can cause heat problems in one cylinder and that might explain some of this.

[Kerrvillian]

I think I posted pictures of my own head failure on Facebook to the OP's post there. In my case, Cylinder 3 had the Grand Canyon of cracks formed between the valves and serious erosion of the head from eating coolant for who knows how long. Head is junk and I'm still in the process of rebuilding the NOS head I sourced and reassembling the engine and fixing other problems in the process.

In my case, the head gasket was NOT blown. All the coolant consumption was coming from the cracks between the valves. Cylinder 3 was leaking enough to both pressurize the cooling system AND hydrolock the engine when sitting after running. Cylinder 4 was also burning coolant, again from the crack in the head.

It's worth noting that the NOS head I've got from BMW has some revisions to it compared to the original head. Not sure if they knew of a weakness like they did on the early Mercedes 603 heads and revised it or what's going on there. I would have liked to replace all the valves and rockers with the head, but Sweet Jumping Jesus are parts expensive for this stupid engine!!! Just the rockers and valves alone are worth more than the car! Yeah, no.

Still waiting on parts to put this heap back together. My goal is to take it to Radwood in Austin this upcoming April. Whether or not that happens remains to be seen.

[gadget73]

I've seen rockers listed on ebay as NOS Ford bits, not sure if you have already looked there but possibly the pricing isn't quite as dumb. E45Y-6564-A.

but yes the prices are stupid. Honestly the whole head crack thing is why I haven't dealt with the head gasket on mine. It leaked externally at the rear of the block where the coolant passage is. I did the great sin of some "mechanic in a bottle" to seal it, and so far its been holding for 3 years now.

[Kerrvillian]

Very helpful! I didn't even think to try looking for the Ford part number. Found a set of 12 NOS listed for $134 shipped. Considering the BMW ones are $33 EACH for the cheapest ones I've found, plus shipping from Europe, that's a steal.

Valves are staying original as they're so expensive as to be a joke and I've already got the head back on the car and I have them lapped in, but those rockers are in pretty sad shape, so that's a big improvement. I don't look forward to fighting those stupid spring clips again, but I'll gladly pull the cam and swap the rockers to have fresh ones in there. Thanks!

[gadget73]

No problem. Is your cam still in good shape? If the rockers are worn I'd wonder about the cam. I'm guessing you already cleaned out the holes in the oil sprayer as well?

[Kerrvillian]

The cam isn't bad. The interior of this engine is pretty clean and the wear to the riding surfaces is pretty minimal. The surfaces of the rockers really aren't bad either, it's the wear to the pivot where they sit on the ball studs in the head that's pretty extreme. Really a crappy design on BMW's part where they rely on a "splash" of oil to lubricate that point instead of forced lubrication.

The oil sprayer has been sent through the ultrasonic and blown out with compressed air and everything else being reused has been cleaned as well. Even the camshaft got cleaned out. This wasn't an oiling failure in my case, so the journals aren't trashed and the lobes are in reasonable condition. Not worried about reusing the cam, but the rockers were definitely something I wasn't happy with due to the pretty serious wear to the pivot point.

[gadget73]

is this one of those things you'd only really notice if the cam was out? I haven't had the cover off mine since I had the injection pump off for a rebuild, and the only poking around the valvetrain I did was to set the lash. The cam lobes and the rockers looked OK there but I didn't look much beyond that.

I had to replace a set of aftermarket roller rockers on a Ford 302 for pivot wear. Same basic lube mechanism there, they are oiled by whatever dribbles out of the end of the pushrod and manages to make its way into the bearings. When I had all that apart for other reasons I noticed how sloppy and rough it was.

[Galahad]

is this one of those things you'd only really notice if the cam was out? ...

You might be able to tell if you have pivot wear by looking down the oiling hole in the rocker - mine was really obvious, but some of them had worn down a couple mm so it might be harder to spot if it's not as bad.

[Kerrvillian]

is this one of those things you'd only really notice if the cam was out? ...

You might be able to tell if you have pivot wear by looking down the oiling hole in the rocker - mine was really obvious, but some of them had worn down a couple mm so it might be harder to spot if it's not as bad.

Mine were REALLY BAD. Look at the wear on the old ball pivot compared to the new one. Worth noting the new one is flat on top, so that's some really deep wear. All 12 were like this.

[Kerrvillian]

Figure since I finally broke down and setup an Imgur account, I'd go ahead and post pictures of the bad combustion chamber on my head. This got bad enough to hydrolock the engine when it sat after running. The crack between the valves oozed coolant for several days once the head came off, same with cylinder 4. Head gasket was NOT blown, which was my first thought of what was wrong. The damage to the head really surprised me. Been chewing on coolant for a LONG TIME.

Up until this thing died at TexFest in October, it really didn't have any running symptoms other than very slowly using coolant, but I also had a weep at one of the cooling hose connections under the intake manifold that's since been remedied. Don't mind the scratches and scrapes on the head surface, that's from me cleaning it with a wire brush to get clear photos.

[Galahad]

You might be able to tell if you have pivot wear by looking down the oiling hole in the rocker - mine was really obvious, but some of them had worn down a couple mm so it might be harder to spot if it's not as bad.

Mine were REALLY BAD. Look at the wear on the old ball pivot compared to the new one. Worth noting the new one is flat on top, so that's some really deep wear. All 12 were like this.

Yup looks just like mine. I replaced all the pivots and rockers when I did the camshaft (which was also toast). Clogged oil spray bar

[gadget73]

oof, thats nasty.

now I'm sort of wondering if my slow coolant loss is something more than the suspected bad rad cap. I've found evidence of coolant drips out of the overflow hose. I have a new cap, will stick that on in the spring and see if that fixes it. May also route the overflow into a soda bottle or something temporarily to confirm the issue. Not 100% sure if its burping from a bad cap, or if its just from top-offs. The bottle on the Continental is mounted on the firewall so there is no room for a funnel. Pretty typical to splash a little into the recessed area around the cap where the overflow tube connects.

maybe this spring I'll pull the valve cover back off and see if I can see anything down on the pivot balls. I should pull and flush the oil sprayer anyway just in case. The cover on the Conti is annoying because of the engine bay shape. The cowl area overhangs the back of the cover, and there are a pair of heater hoses laying against the back of it. Fishing the cover in there with the vac pump, the hoses, and getting the gasket in position is a chore. The BMW looks easier, seems like you could pull it basically straight up. Also your hoods go pretty near vertical so it doesn't have the head-bonk issue I have.

[Kerrvillian]

I suspected a bad rad cap myself and ruled that out when a new one didn't resolve the issue. I could occasionally smell antifreeze when pushing the engine hard, and at TexFest noticed I had a little bit burp out of the overflow line before it let go. Not something it had been doing before, but certainly something to pay attention to.

Cracked heads and blown gaskets are not new to me on 80s German diesels. I went through this with my old Mercedes 300SDL and helping another friend with his. It's typically pretty obvious when the head cracks on those. You get overheating, particularly when the engine is under load, and you have a coolant loss you can't account for. Usually slow, and sometimes you have pressure in the cooling system after the car has gotten cold, but not always.

The E28 hood opens at a less than generous angle stock. Fitting it with E23 hood struts makes it open much wider and makes it easier to work on for anyone who isn't a midget or 8 year old. I wish they had a "Service Mode" like the Mercedes where it latches straight upright for servicing. Seriously, what a GREAT idea that nobody else seemed to use.

The valve cover will come straight out of the engine bay, but it's still not as easy as just removing the charge pipe and hold down bolts. That stupid timing belt cover in the front is in the way, so you can't get it off without removing that first. Just so many GENIUS designs on this engine that prove those who designed it never had to work on it and never bothered to think about those that did.

I'm hoping to get this thing closer to running this weekend so I can torque those head bolts the final 90 degrees. We'll see. If I post pictures of the car on fire without any context, assume the job went poorly.

[gadget73]

hm, for some reason I thought the E28 had that service mode thing like Mercedes does.

anyway, is there a straight enough shot from either the injector or the glow plug to get a look in the cylinder using a bore scope without having to pull the head? Starting to get a funny feeling about mine. Pulled it out this weekend and the coolant bottle was mostly empty. Its been sitting for 3 months, and there wasn't anything on the ground. Started fine and I've never had any traces of moisture in the oil.

[Galahad]

hm, for some reason I thought the E28 had that service mode thing like Mercedes does.

anyway, is there a straight enough shot from either the injector or the glow plug to get a look in the cylinder using a bore scope without having to pull the head? Starting to get a funny feeling about mine. Pulled it out this weekend and the coolant bottle was mostly empty. Its been sitting for 3 months, and there wasn't anything on the ground. Started fine and I've never had any traces of moisture in the oil.

Both of those look into the swirl chamber, not the cylinder. You're a bit out of luck, although you may be able to sneak a peak around a valve

[Kerrvillian]

hm, for some reason I thought the E28 had that service mode thing like Mercedes does.

anyway, is there a straight enough shot from either the injector or the glow plug to get a look in the cylinder using a bore scope without having to pull the head? Starting to get a funny feeling about mine. Pulled it out this weekend and the coolant bottle was mostly empty. Its been sitting for 3 months, and there wasn't anything on the ground. Started fine and I've never had any traces of moisture in the oil.

Nope. No service mode. BMW liked to make it as hard to work on their cars as possible. Look at the backwards opening hoods for more proof (E21/23/34/32/etc). E23 hood struts make it open wide though with no other modification required. Great for tall people with a tendency to smack their forehead all the time due to clumsiness and inattentiveness (me).

If the head on your bore scope is small enough, you MIGHT be able to snake it through the hole in the swirl chamber to see into the cylinder if you pull the injector out. Otherwise, it's try to see past a valve if you're lucky. Not great access to get into the main cylinder on an IDI diesel. Mercedes prechambers pull out with a slide hammer and give access direct to the cylinder, but these M21 swirl chambers are pressed in from below and cannot be removed and installed easily.

[gadget73]

any chance you can get me a rough measurement on that opening? I don't currently have a borescope but I'm not opposed to buying one if I can find one small enough. Even if I can't get a great view, if I can see enough to get a look at the top of the piston to see if its got pock marks it ought to be an indication.

[Kerrvillian]

I'll get you one this afternoon unless someone else beats me to it. I've still got the old head kicking around in my storage container

[Kerrvillian]

Here's your measurements. Note in the last photo, you can see daylight, so assuming the head on your bore scope is small enough, you should be able to snake it in there to take a peek.

[gadget73]

so looks like maybe 1/4" / 6mm is about my upper limit for having any hope of fishing through there. Not really expecting much, just thinking if I can get it lined up enough to see the top of the piston through the hole it may tell me something without having to pull the head. If 5 look OK and one looks like the back side of the moon its time to start buying parts.

Appreciate it.

[Kerrvillian]

IT LIVES!
https://imgur.com/GTNGMpc

[Galahad]

IT LIVES!
https://imgur.com/GTNGMpc

Definitely sounds like a diesel!