Head gasket - rebuild head, nothing or whoole motor?

[winstontj]

I would never advocate putting a fresh/performance head on a stock bottom end with 220k but I've also never been faced with a blown head gasket either. Since this is our primary mode of transportation (we both live in boston & walk/subway to work) and summertime is here I cant have the car down for more than a long weekend.

Should I risk it and simply just do a head gasket? Buy a new (used) head, build it (porting, valves, cam, etc.) and install that or should I get an entire motor, build it and throw that in?

Because I have no idea what could really be wrong (cracked head) and I have no idea what may or may not have been done to the inside of the motor (outside has cam, Split Second, exhaust, BBTB, MAF conversion) I am in uncharted terratory. I could be walking into a stroker motor, non-stock pistons, CC machine work, different (bigger) valves, etc. This is why I hate buying undocumented cars!!! PPO did lots of work & since the car has so many external mods and came with dyno sheets, etc its a risk to build a head without knowing what you are putting it on... nevermind strapping a head on to a 200k+ block... But then I really dont want to be forced into a time & budget situation with the eventual plans to buils a motor for this car.

How likely is it that I have a cracked head? I have only owned the car for three or four months so I have no idea about its past, if it ever got hot, etc. do these heads crack like (all BMW) m10 heads do? Chances are that the PPO reused the head bolts because they look reused (wrench marks on the bolt heads) but you never know...

Any thoughts? I really want to just do a head gasket, in one long or two days, and then just drive the effing thing! What are the chances that I'll pop the head to learn that the head is cracked & how dumb is it to just throw a head gasket in there without a machine shop pressure testing the head? Is there any way for me to ghetto/back alley pressure/crack test the head? If not and you guys tell me its dumb to not get it checked out then I need to find a head and go down that unwanted road.....

Thanks fr reading & thanks for any thoughts!

[jlevie]

There's no way to tell what is wrong until the head is off the engine. And you aren't going to be able to tell what mods to the head might have been done until the head is off and apart. If the work has to be complete over a long weekend either a replacement head or replacement engine is probably the only workable solution. On a +200k engine I think I'd lean towards a lower mileage used engine.

After disassembly and hot tank cleaning, you can check for cracks with dye-penetrant testing in lieu of a pressure test, but even that requires special equipment that you aren't likely to have or have access to over a weekend. Heads can crack, usually as a result of an overheat, and any time a head problem is present it is silly to not have the head checked for cracks.

[StereoInstaller1]

I think it matters a whole bunch what condition the bottom end is in.

Have you done a leakdown? How about a compression test, with and without motor oil? If your cooling system is not holding pressure, but you are not mixing coolant in yout oil, there is a blown HG. Good compression but mixing? Cracked head, likely as not between 4&5 on the intake side...in the lifter valley.

You said the PO did a bunch of work...you sure it has 220K?

Hoping for the best,
Luke

[winstontj]

I think it matters a whole bunch what condition the bottom end is in.

You said the PO did a bunch of work...you sure it has 220K?

Hoping for the best,
Luke

ODO says 220k. Car rolled off the line as an automatic, was gently driven to ~140k by a female university professor in Cambridge, MA. PPPO bought it and drove it a bunch... dont know anything other than the PPO bought it from a used car dealer running poorly with a bad auto box for cheap. PPO put in a 5spd & did a ton of work - to the tune of $12k in 2000. PPO sold the car to the PO about two years ago when he was in a jam & needed cash. PO drove it and knew nothing/did nothing with m20/e30's.

I'm pretty sure it has correct milage but I have no idea about he internals... Only one way to tell though. PPO put a cam in - bet he reused the head bolts.... All I want is to drive the thing long enough that i can build an ITB motor for it....

[Mike325]

If the car has had $12k put into it, I bet there was some stuff done to the engine besides the head. Does your car have $12k worth of stuff on it minus any possible engine internal stuff? My bet is what you are leaning twards. The po that did the cam, reused the bolts, which is retarded, and did not torque the head the right way. This caused warpage of the head and fucked the gasket.

I would take the head off and have it looked at. Hopefully it is still useable and they can do whatever they need to get it 100% i would also check the block for straitness with the head off. Has you car ever overheated?

[rcko]

dude I hear you... a month ago I went through the same thing and after pricing repair shop and their engines I decided to do it all myself...

What I did is find a used working $300 160k miles M20 engine, refreshed its hoses, water pump, timing belt, thermostat, spark plugs, rotor, distributor, valve cover gasket, rear seal, oil pan gasket, etc and swap that puppy into the car. It has taken me about 3 wknds of wrenching, ~8 hrs Sat and ~5 hrs Sunday, to get it all sorted out and ready to install. I never done anything like this before so it is just me and my Bently slowly taking my time and dealing with a lot of electrical gremlins left behind by the PO who instead of fixing harness just hard wired everything. If you got help and know what you doing you could easily do this in a long weekned.

The plan is for the old 265k mile engine to get slowly built up and then put back in.

[winstontj]

The car easily has $12K into it outside the engine: sterio- decent Alpine deck, subs, amps, alpine speakers (shitty install and equipment chioce but not cheap, at least $2K installed), was an auto, now a 5spd... no idea what a 5spd swap goes for, rear 4.10 diff bumped up to 40%, repaint (the right way removing glass & trim) & properly addressed battery tray & driver's side floor rust, fancy headlight upgrade (no idea what you guys call it), euro grilles the kind with eyebrows stock, recaro (BMW sport seats), rear seats with armrest & headrests, Split Second MAF conversion, 4 knob box with the LED display, SS brake & clutch lines, ST sways, H&Rs, Billy Sports, BBTB (possibly extrude honed intake), e36 exhaust, Bav Auto chip, F&R strut bars, BIG plug wires, and that doesnt even touch the motor.

There is $12k there.

I have a buddy with an HVAC fiber optic scope you can put into the spark plug holes and see the CC... I'll do that and take a look at the hone marks & piston tops. This car is turning into a total shit show....

[FredK]

Sounds like a pretty solid car besides the engine troubles.

Hopefully you can get 'em sorted out. Otherwise, you're gonna have to drop in an S52. :mrgreen:

I wonder if Mike325 still has the M20 he was selling a month ago? That engine was pretty pristine and bone stock--I sold it to him!

[StereoInstaller1]

Dude, go buy a cheapass compression tester and a small "hobby" syringe.

Pull all 6 sparkplugs, unplug the coilwire.

Sit a buddy in the drivers seat, put the compression tester in the #1 cylinder, hold the throttle open (have buddy do that) and crank the motor like 3 seconds.

Write down your results for all 6.

Do the same thing again, except before cranking, add 20cc whatever motor oil you have laying around to the cylinder you are about to test. Once again, write the results down!

Post the data on here. If this entire process takes more than an hour, or takes more than $20, you are doing it wrong.

Luke

[Mike325]

Sounds like a pretty solid car besides the engine troubles.

Hopefully you can get 'em sorted out. Otherwise, you're gonna have to drop in an S52. :mrgreen:

I wonder if Mike325 still has the M20 he was selling a month ago? That engine was pretty pristine and bone stock--I sold it to him!

I don't

If you want a hand doing this, give me a pm, I will be happy to help you get this thing sorted out.

[winstontj]

Was going to buy that motor (i think) but I went away to Italy for a few weeks.... Oh well things come and go. I'll get another one. Sterioinstaller I did a comp test when it was new and I got ~150psi/cylinder. All within 5% of each cylinder. I know I need to do it again - haven't got the time to drive to the storage unit to get the comp tester, then do the test... maybe I'll just buy another one.

Pretty sure its the head gasket. What do I need to ask a mechanic to test for in the coolant??? Is it carbon monoxide?