m43b16 mysterious overheating

[kukkakeppi]

Don't make it so complicated, just do it.

Okay I will

[BimwadM42]

Thank you a lot for this. I'll try this method as soon as a new WP's been arrived and installed. But I've still got few questions regarding your manual:
3) wouldn't the coolant spill out from bleeding screw since it's been removed?

It's not necessary to completely remove it; just loosen it enough to that there is an opening for air and fluid to escape. The amount of fluid that does escape, when (moderately) revving the engine is trivial.

4) how quickly will the engine suck coolant in? Is there enough time to start the car and rush pouring more coolant before the level drops too low and it sucks air in?

And overall running the engine without reservoir cap. Aren't these cooling systems supposed to work pressurized? (When coolant warms up, it expands causing some pressure--> more pressure--> higher boiling temperature). And without that pressure is it possible for the coolant to start boiling which produces more air in the system?

The level is drawn down relatively slowly, and it's not difficult to keep the tank from emptying. Even if it were, it's not a case like where running the brake fluid reservoir dry would necessitate re-bleeding. The cooling system is circulatory; the brake system is not.

You only need to get the engine warm enough to for the thermostat to open, and the complete system to flow openly. That should at occur at 92C for a stock thermostat, below the 100C boiling point for pure water at sea-level atmospheric pressure. The coolant mix will give some additional margin, and in any case, once the thermostat is open, it doesn't take long to bleed. The wait for the engine to warm up requires the most time.

Another thing I forgot to mention is that elevating the front of the car can help. It's not necessary to raise it on jacks or something like that. Simply parking on a slight incline is sufficient.

[spyderg0d]

Initially, i fill the system from the top radiator hose. I pull the hose off the top of the radiator and pour coolant into it until ot doesnt take any more. Then i pour it in a funnel into the top of the radiator until its at the top. Connect the hose. Then i just blow into the coolant jug through a rag so i dont eat coolant. Fill the jug to the line although it wont need much. Blow into it some more and then you can bleed it while its running.. Any air bubble will be at the top of the radiator already and not in the thermostat housing.

[kukkakeppi]

Okay guys so the new waterpump arrived and now it's been installed. The bleeding was done by using instructions below. And guess what. It still runs hot. This is the exact position where the temp cauge likes to set:
20200608_152245.jpg

I'm running out of ideas. I took the car for a longer ride (about 50km) and the temp cauge won't move from that. Well, on long engine brakes it slightly moves backwards, and never reaches the red. (I know it is no good to drive with that hot engine but guess I don't care anymore..)
The hottest part of the engine was about 105 celcius degrees (from IR-meter)

BimwadM42

I've flushed the cooling system on an M42 more times than I care to remember, including draining the block, and have not had an issue bleeding the system by following these steps:

1) HVAC controls full hot; ignition ON (electronic valve)

2) open radiator bleed screw

3) fill expansion tank until it is full, without spilling over

4) start engine, and add coolant as allowed as it is drawn into the engine

5) allow engine to reach operating temperature, again while watching level in expansion tank and adding coolant as needed

6) once up to temperature, with thermostat open, and upper hose clearly hot, rev engine until a mostly solid stream of coolant and few bubbles emerges from the bleed screw; return engine to idle.

7) snugly bleed screw, but do not over tighten (!*), turn engine off.

8) button everything back up, go for test drive, and allow engine to cool

9) top off to the Cold/Kalt line as needed.

[spyderg0d]

Well. Maybe your coolant temp sensor is bad.

- - - Updated - - -

Sometimes i put pressure through the cooling system while its running or revving, It forced the air bubbles through much faster.

[kukkakeppi]

Well. Maybe your coolant temp sensor is bad.

- - - Updated - - -

Sometimes i put pressure through the cooling system while its running or revving, It forced the air bubbles through much faster.

Both of the temperature sensors has been replaced. (The one for the ecu and other for the temperature cauge)

[samy01]

So which parts of the cooling system did you not replace yet?

[kukkakeppi]

So which parts of the cooling system did you not replace yet?

Well, heater core and its valve, both are fine no leaks at all. Also some of the water hoses are original but they're not leaking at all, double checked.
I'll list here one more time all the parts I've so far replaced:

-Upper and lower water hoses
-Thermostat
-Waterpump
-Radiator
-the plastic water outlet in the rear of the engine
-radiator cap and bleeding screw
-both temperature sensors
-all the hoseclamps that has had to been removed

[samy01]

I personally think something during bleeding went wrong and there's still air in there. Step 6) of the bleeding procedure says rev engine (with heater on full hot), and i've learned you realy have to rev up to 4000rpm minimum in order to get that air flowing out of there. How high did you rev?

[kukkakeppi]

I personally think something during bleeding went wrong and there's still air in there. Step 6) of the bleeding procedure says rev engine (with heater on full hot), and i've learned you realy have to rev up to 4000rpm minimum in order to get that air flowing out of there. How high did you rev?

Not sure because I throttled up by pulling straight from the throttle cable. But sounded like just about 4000 rpm, didn't rev up higher since the coolant was splashing all around even with that high rpm

[spyderg0d]

Are you sure you have all the coolant hoses connected right? The only other thing is your new thermostat has to be faulty or radiator is clogged.

[kukkakeppi]

Are you sure you have all the coolant hoses connected right? The only other thing is your new thermostat has to be faulty or radiator is clogged.

Yes, I'm 100% sure that all the coolant hoses are connected right, there ain't that many hoses in this engine. Radiator is not clogged since it is brand new and I've flushed it like 5 times to make sure it flows correctly. It can't be thermostat neither because I've tried another one (check few previous posts of this thread)

[BimwadM42]

Given the situation, these would be my suspects:

1) air in the system. Engine water pumps move a surprising amount of fluid, so I don't think it's necessary to rev to 4k and hold it there; the goal is just to get enough flow in the system to expel the air pockets.

2) defective parts -- thermostat, temp sensor. However unlikely it is for one or the other to be faulty, it can be discounted entirely. It's possible to test both. I'm not familiar with TOPAZ, but do know of Meyle. When they first appeared, they were not well thought of. I don't know if things have improved, and that has changed, but I always try to stick with the OEM brands for my cars, and avoid aftermarket, especially for functional parts. These cars are old, and even though parts availability is still good, I've found the quality can be inconsistent, even with genuine BMW parts. What's still being manufactured for the parts channel probably doesn't have the same level of QC as when the production channel was active and cars were still rolling off the line and subject to closer monitoring.

3) obstruction in the circuit. Perhaps unlikely, since the car ran fine for at least some time before issues appeared, but beyond that, it does have an unknown history.

Unfortunately, the buffered temperature gauge is halfway between a real gauge and an idiot light, and doesn't truly reflect what's going on except at the extremes, and one wide middle, so it makes diagnosis harder. You can try a moonshot, and pull the cluster fuse (#31, IIRC), to reboot it without pulling the battery leads. That used to be an old trick to fix the wonky fuel gauges when the ignition was left on during refuelling.

One last thought -- did you use the install and connect the proper sensor for the gauge and DME, respectively? I don't know if they can be mistakenly mixed up, but that's also a possibility.

[samy01]

I don't think it's necessary to rev to 4k and hold it there

I never said hold it there. I wanted to say that 2-3 rev pushs to 1200rpm won't do it and that you have to give it a little higher rev pushes, fore example 4000rpm. I once bled a 318i and i couldn't get the air out, but after a little higher reving the water level dropped significantly, meaning a lot of air came out.

Just an idea.

However, i think you didn't bleed it right. Given that you don't really know how to bleed this car (Your bottle experiments in the beginning), and how you strictly have to follow the instructions because you apparently didn't understand the principle of the bleeding process makes it seem that you wouldn't recognize if something would go wrong during bleeding, and if the bleeding was successful, because you simply work by the instructions and not from your own experience and knowledge. Everything is new, it should be working by now.

[kukkakeppi]

I never said hold it there. I wanted to say that 2-3 rev pushs to 1200rpm won't do it and that you have to give it a little higher rev pushes, fore example 4000rpm. I once bled a 318i and i couldn't get the air out, but after a little higher reving the water level dropped significantly, meaning a lot of air came out.

Just an idea.

However, i think you didn't bleed it right. Given that you don't really know how to bleed this car (Your bottle experiments in the beginning), and how you strictly have to follow the instructions because you apparently didn't understand the principle of the bleeding process makes it seem that you wouldn't recognize if something would go wrong during bleeding, and if the bleeding was successful, because you simply work by the instructions and not from your own experience and knowledge. Everything is new, it should be working by now.

Alright then. Guess have I tried bleeding by working exactly as the instuctions say. Honestly I've bled the car like 15 times during the past half year trying different ways and there's absolutely no difference. And there's nothing wrong with the bottle method, I actually got that tip from another forum where a large group of people recommended it. The point of using the bottle is to make its level of coolant to be the highest point of the cooling system. (Actually the bleeding screw is usually the highest point but the bottle makes it even higher and prevents from splashing the coolant). Thus the possible air in the system gets pushed out by squeezing the coolant hoses.

[samy01]

Raising the level of fluid won't help you if you have a "reverse syphon" situation, for example in the cylinder head, where there' is air trapped. Imagine the shape of an upside down "U", if there's air trapped in there, it won't help raising the fluid level, because the air has nowhere to go.

[spyderg0d]

210f is within the normal range. I think its 190 to 210.. Maybe the needle on your cluster got spun..

[Eric93se]

Is the replacement rad a dual core unit? Some super cheap ones are single.

Also as spyder said, your 105C is not excessive at all. Is your fan coming on? If that 105 is accurate then I would also say the gauge may be bad, maybe swap out the cluster.

[kukkakeppi]

Hi!
Got some interesting news.


So I once again came up to conclusion that the problem must be thermostat related. So I took my MEYLE thermostat and drilled 5mm hole to the back plate. This MEYLE is the one that doesn't seem to let any water through.
And boom. No overheating. The temp needle stays in the middle. Only the heater blows now a bit more cool air than before. Not sure though if the t-stat opens or not. Is the 5mm hole big enough to let enough coolant through to cool the engine? Or is it that big that it is like there's no t-stat at all? That might cause some problems as winter arrives and temperatures drop below -10C

[spyderg0d]

Eh.. It will take longer for the engine to warm up. May create condensate in the crank case. Cvv problems.. Just keep an eye on it when it gets cold.. Or you can get a working thermostat.

[Eric93se]

I think you will be fine.

If you want, take a pic of the thermostat housing and mark where the hole is. If this fixed the problem then you had air trapped.

[kukkakeppi]

I think you will be fine.

If you want, take a pic of the thermostat housing and mark where the hole is. If this fixed the problem then you had air trapped.

thermostat.jpg

I drilled the hole directly into the actual mechanism. As I've understood the upper plate sniffs the coolant temperature from the head thus pulling the lower plate away from the housing allowing the fresh coolant to flow in.
I don't know, was I really that unlucky I got two brand new t-stats that were both already stuck in closed position? Yeah, shouldn't really buy else than OEM parts but still.. two brand new parts.

Here's more visual presentation of my thoughts how these t-stats are supposed to work:
circulation.png

So these t-stats seem to be like 2 staged. The upper plate detects the hot water and controls the lower plate. That's why it is not possible to operate completely without thermostat (I tried with only the housing without the t-stat leading to overheating once again..) because the hot and cold water would mix in wrong place distorting the circulation.