(Yet another) M42 top end refresh and engine reseal (mid-2021)

[econti]

Coolant wise, I find that it helps immensely to pre-fill the heater core and then massage the hoses there, as that's almost always where the air bubbles are.

I wouldn't stress too much about priming the pump. There'll be oil residue on the bearings still, when its cranked it'll suck the oil up through the pump in a few revolutions, usually.

[bmwman91]

If you packed the oil pump with grease, it should prime up nice and quick. There's probably nothing to worry about there.

As far as the coolant, as long as the little bleed groove in the thermostat housing is clear, 95% of the air should bleed out within 20 seconds of starting. Most of the "nightmare" stories people have are a result of gasket sealer or corrosion blocking that groove. Since you have been very meticulous, I'd bet that you can just connect all of the hoses and fill the system via the expansion tank. When I swapped engines last year, that is all I did, not worrying about the air in the heater core since it came out shortly after the engine came up to temperature. Just fill the expansion tank all the way and keep topping it off until the level stops dropping, then start the engine, crack the bleed screw, and add coolant as it continues to get sucked in so as to maintain approximately the proper level.

[jsnppp]

Coolant wise, I find that it helps immensely to pre-fill the heater core and then massage the hoses there, as that's almost always where the air bubbles are.

I wouldn't stress too much about priming the pump. There'll be oil residue on the bearings still, when its cranked it'll suck the oil up through the pump in a few revolutions, usually.

Thank you. So, open one of the smaller hoses at the firewall and fill there first? I can do that.

Fingers crossed on the pump priming!

[jsnppp]

If you packed the oil pump with grease, it should prime up nice and quick. There's probably nothing to worry about there.

As far as the coolant, as long as the little bleed groove in the thermostat housing is clear, 95% of the air should bleed out within 20 seconds of starting. Most of the "nightmare" stories people have are a result of gasket sealer or corrosion blocking that groove. Since you have been very meticulous, I'd bet that you can just connect all of the hoses and fill the system via the expansion tank. When I swapped engines last year, that is all I did, not worrying about the air in the heater core since it came out shortly after the engine came up to temperature. Just fill the expansion tank all the way and keep topping it off until the level stops dropping, then start the engine, crack the bleed screw, and add coolant as it continues to get sucked in so as to maintain approximately the proper level.

Thank you for your reply. Am a bit nervous after reading the horror stories.

Oil: Thats the thing. I put grease in it, but didn't pack it - which by my definition now is that it is completely full of grease, no air pockets. Wish I had! But there is some grease in there.

Coolant: I made sure not to have that bleed passage in the thermostat blocked, based on your older posts on the topic. I forgot about the bleed screw, greatly appreciate the reminder. I'll still take a look at the firewall hoses and see if I can add any there first. I don't mind the extra step.

It's 24F in Austin this morning, moving up to the mid 50s. Probably try around noon, depending on how this all goes. Still drinking coffee and contemplating what is all about to happen.

Thanks folks. Truly appreciate the second set of eyes and comments.

[jsnppp]

Shop only had a gallon of anti-freeze, which I now know is not enough! Heading out to buy more.

Getting close.

[jsnppp]

It runs!

A bit of a journey. No leaks (yet), very tappity for a few minutes once started. Let it run and tappity is relatively gone (whew), but it won't drop in idle. Its a 1100 rpm. I let it get to a bit past midway in temp gauge waiting to see if fan would kick on but no go. Possibly coolant temp sensor issue, letting the car think it's cold thus keeping idle high.

Daughter is very happy! I am very happy!

More soon, with photos and video.

[bmwman91]

Great to hear! Did the oil light shut off pretty soon after starting?

As far as the high idle and fan, I am not sure if that is related to the temp sensor or not. I don't believe that these things will idle at 1100RPM when cold, but then again I live somewhere where it almost never gets below 35F lol. A stuck high idle is usually a vacuum leak, although that sounds unlikely. Since I have not had any A/C in the car for well over a decade, I can't help much with what behavior to expect from the aux fan lol.

[econti]

Even with a massive vacuum leak it'll still try maintain the usual idle speed, the ICV can compensate for a lot. Its more likely that the temp sensor is bad, which is easy to tell if it's running really rich. Otherwise somebody may have messed with the idle screw, if it's wound up too far the computer will think you've cracked the throttle a bit and so won't use the ICV to bring it down.

[jsnppp]

Ok, here it is - the walk through...

[Before I forget, all with the car nose probably 12in in the air. I have it on jackstands on the front most frame rails. No front wheels. I mention this because it could impact the oil and coolant filling for someone reading this in the future.]

First we filled the coolant. Opened the top hose for the heater core and filled it till it felt like it was done. Heater was "on" in the car. At some point adding coolant wasn't creating bubbles, it felt like it was just filling the block, so we stopped and closed up the hose.



Moved to the radiator. Opened the reservoir tank and filled to the top. Kept refilling as it dropped. At one point it stopped dropping. Opened the bleeder valve and let it bubble and filled it a bit more. Closed the bleeder when done.



Then we moved to oil. Put 1 quart of dino oil (not synth) in from the oil filter (removed the cap and poured slowly into the center tube) and then 4.3 more quarts in through the oil filler cap on the valve cover. I had Pennzoil 20x50 around and so used it, figuring it was thick and would help with the priming (maybe). I'll change it again after a 100 miles or so anyway.



We cracked open the allen key bolt on the side of the oil filter housing but didn't remove it, I saw some wet threads and figured there was oil getting to it somehow so just closed it up again. I'd go down that road again if needed.

Removed fuse 11 for the fuel pump. Pulled the plugs.

Turned the key and just a click. For whatever reason the battery wasn't up to the task and so I swapped in another. Ugh.

Turned the key and let the motor spin. I let it turn over about 5 seconds and repeated it several times. I was looking for the oil pressure light to go out. Eventually I let it crank for 15 seconds or so and the light dimmed. DId it again and it went out. Tried it again and it went out right away. Awesome!

Installed the plugs and put fuse 11 back. Spark plug wires took us an extra 15min. It wasn't as obvious as we had thought.

Next tried starting it in earnest. Let it crank maybe 10 seconds at a time - didn't give me the feeling it wanted to get going. I even put a bit of starting spray in the airbox a couple of times. No love.

Checked a bunch of things but eventually reviewed the coil distribution block. The wiring to plugs 1 and 3 were swapped. Didn't know that at the time but they felt wrong based on the way the plastic housing was bent.



This time it fired up. (Videos on the next page, the photo links break when I add them here)

Very clackity at first as you can see. Let it run because thats what it was supposed to do while it oiled up. Eventually shut it down. Started it again and revved it a bit more and held it. The engine started to steam/smoke as the cleaning fluids began to burn off. Shut it down again and started it and this time after a bit it quieted down considerably.

Here it is after it quieted down. We have a video where it noticeably changes that I'll add. (Videos on the next page)

I'm happy to report that it starts quickly, after a crank, maybe two. I'll try again in the morning when it's cold just to see how it behaves.

Now we get to move to the next phase of this journey - getting it to run right. It "idles" at about 1200rpm. Smooth overall but with an occasional stumble. I tried spraying carb cleaner to check for leaks but nothing uncovered yet. Haven't cleaned the IDC, but it does hum a bit when the key is turned.. I pulled the IDC plug while it was idling and it didn't change anything. Possible culprit.

We definitely consider this a successful day.

[jsnppp]

Great to hear! Did the oil light shut off pretty soon after starting?

As far as the high idle and fan, I am not sure if that is related to the temp sensor or not. I don't believe that these things will idle at 1100RPM when cold, but then again I live somewhere where it almost never gets below 35F lol. A stuck high idle is usually a vacuum leak, although that sounds unlikely. Since I have not had any A/C in the car for well over a decade, I can't help much with what behavior to expect from the aux fan lol.

Thanks! Totally stoked. Yes, it turned off relatively quickly, but still longer than I wished :-)

Good point, that is the condenser fan, not an auxillary cooling fan. So, perhaps it didn't reach full operating temp. I was too timid to let it get too hot. Should it read midway or higher on the dash gauge?

Edit: It just occurred to me that without the front shroud on the fan, it likely wasn't drawing much air through the radiator. I'll add that tomorrow.

I'll do a closer review of the vacuum lines and the IDC tomorrow, also need to check the throttle body, maybe I missed something.

[jsnppp]

Even with a massive vacuum leak it'll still try maintain the usual idle speed, the ICV can compensate for a lot. Its more likely that the temp sensor is bad, which is easy to tell if it's running really rich. Otherwise somebody may have messed with the idle screw, if it's wound up too far the computer will think you've cracked the throttle a bit and so won't use the ICV to bring it down.

Ok, good point. The front most temp sensor in the head may be the issue. We never drove the car except around the block a couple times so I can't say I know it's behavior before the reseal. The idle screw (on the top of the throttle body, right?) doesn't look messed with but whos to say..

[bmwman91]

The temp needle is typically straight up, maybe one needle width higher then the middle mark on occasion, but more commonly a little lower due to thermostat aging effects over time. As you noted, the missing shroud does impact the cooling function of the radiator & main fan. You may also have an air bubble in the head which is causing the temp sender for the gauge to read high. I figure that you know this already, but there are 2 temperature sensors: the sender unit for the instrument cluster (1 terminal), and the sensor for the ECU (2 terminals). One known fault is for a wire in the ECU sensor plug's boot to fatigue and break, going open circuit. The ECU sensor is the more-forward one I believe, and you can probably get at the boot without taking anything apart.

I am looking forward to a video of it running!

[jsnppp]

Thanks bmwman91! I'm going to investigate that forward sensor today and install the fan shroud too.

[jsnppp]

Working on videos..

I started the car this morning. It began at a nice 950 rpm and I thought it was fixed! Then I watched it slowly climb to 1200.

I put the shroud on and also verified the temp sensor wires were intact.

I did notice that disconnecting the idle control valve did nothing. So I removed it and am soaking in cleaner for a bit. The valve does seem to move..

Does the arrow point up? Thats how I installed it. I seem to find reference that it points to the intake manifold (up)...

More soon.

[bmwman91]

The arrow indicates air flow direction, so yes pointing to the manifold is correct. If it is properly clean, you should be able to shake it (rapidly rotating it along its axis) by hand and hear the little door banging around on its stop. It usually needs to be pretty seriously gummed-up to get stuck open, but it is certainly not unheard of!

I had decent luck cleaning mine by running some 99% isopropyl alcohol through it and rapidly connecting/disconnecting it to a 12V battery with alligator clips. Try not to submerge the whole thing as the solvent will get down into the lower area with the coils and stuff. It should not hurt it, but greasy stuff can work its way in with the solvent. If you want to make sure things are dried out, you can bake the thing at 175-200F for a couple of hours when done (there's nothing my wife loves more than coming home to car parts in the oven lol).