Coolant Flow Diagram

[Genes1s]

So, this is kinda silly questions. Does anyone have the flow diagram of the coolant path in our E36 M (S52)?

I already asked in respond to another thread but perhaps I can get answer here since we have more traffic here.

This started as I was looking to mount my water temp sending unit. So far, other than doing it in the head, which mine didn't have any extra port, is to do in the t-stat housing. I found this pic, which looks like the sender it is placed in the flow of the upper radiator hose (NOT in the direction of the thermostat opening).
housing%202.JPG
Attachment 648019

Based on the pic above, the upper radiator hose would carry the "hot" coolant goes in the radiator but If I understand how the thermostat works, the thermostat sensing part is in the engine head, which in this case in the flow path of the lower radiator hose NOT the upper radiator hose. UNLESS there is an opening/by pass on the block where the hot coolant goes to the thermostat side of the housing and activates it when it reaches certain temperature and retracts the thermostat open to allow the cold coolant from the radiator to go to the engine.

so, which diagram is it?
This
IMG_5674.JPG
or This
IMG_5673.JPG
or???

Thanks

[bluptgm3]

Your second diagram is more correct.

This is the M54, M52 is similar -
https://www.bimmerfest.com/forums/sh.../topics/449008


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[pbonsalb]

There is a small bypass hole in the thermostat housing. I have mounted a 1/8 NPT sender there before and it has worked. You can also get an adapter fitting to use the throttle body heater port in the head if you are no longer heating your TB. Many have gotten rid of the heater circuit with no ill effects. Mine has been gone for over 10 years and I drive in winter in NH.

[BimmerBreaker]

M54 actually flows a bit differently as far as specific routing... but its the same as far as which hose is hot/cold

The upper hose is the hot hose on every BMW I've worked on. Makes sense to me, heat rises after all, so have the hot inlet on top of the radiator and take the cool coolant out at the bottom.

I also imagine you'd want the sensor on the cold side of the thermostat. If its supposed to regulate anything, you'll want to be regulating the temperature of the coolant going into the engine - not coming out. So the picture with the sensor in the housing does look wrong to me. Though - we don't know what their intended use for it was, maybe they had a reason for that, or maybe they just wanted to measure coolant outlet temps...

[bluptgm3]

The upper hose is the hot hose on every BMW I've worked on. Makes sense to me, heat rises after all, so have the hot inlet on top of the radiator and take the cool coolant out at the bottom.

I also imagine you'd want the sensor on the cold side of the thermostat. If its supposed to regulate anything, you'll want to be regulating the temperature of the coolant going into the engine - not coming out. So the picture with the sensor in the housing does look wrong to me. Though - we don't know what their intended use for it was, maybe they had a reason for that, or maybe they just wanted to measure coolant outlet temps...

I would want to know temperature of coolant coming out of the head/block to validate that the cooling system is working as intended.


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[BimmerBreaker]

I would want to know temperature of coolant coming out of the head/block to validate that the cooling system is working as intended.


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I imagine most people doing this are looking for something to trigger an aux fan or supply tertiary data to the driver - and knowing the temp of the coolant going into the engine is much more useful than knowing the temp of what is coming out.

But to humor your statement - wouldn't it stand to reason that the coolant going into the engine determines the cooling efficiency of the engine much more than the coolant outlet temp? The outlet temp will be hot no matter what the cooling system is doing, ie. if its operating well or totally failed, the outlet will be hot - but if the coolant inlet temperature starts creeping up, you know the cooling system is no longer operating properly. The coolant outlet doesn't really matter in an abstract sense, all that matters is that after the outlet, the water pump pushes it through the radiator where it is cooled and enters the engine again. It's that process - the cooling - that is critical, and that is what would be measured by a coolant inlet temp sensor.

The only time I'd personally find a coolant outlet temp sensor useful, is if I also had a coolant inlet temperature sensor so I could compare the two values and see how much heat the coolant is taking from the engine

[hc1001]

If your thermostat is stuck closed, it will always read cool and you will overheat. Your gauge will seem like everything is good but its not.

[Genes1s]

For me, the additional water temp gage is to make sure that I have enough warning when the engine temp start to creep up, putting it in the block at the hottest section would make sense but that seems way too much work for now. So, seems like the putting the temp sender on the hot side of the thermostat housing is the next best choice. Although I like the idea of having another temp sensor to monitor the cooling system efficiency, but perhaps that's for another day.

Thanks guys.

[pbonsalb]

This is out of stock but you get the idea and can find other parts to make your own.

http://www.trmtuning.com/product/trm...-temp-adapter/

You do need a sender that fits and some are too long or too fat and will bottom out in the adapter or not fit through it.

There are also universal sender holders that fit in the upper radiator hose. Cut the hose and insert it. I forget the size of our hoses. 1.375? 1.5? 1.625?

If you have two fans, separately controlled and properly installed, you really don’t need to worry.

[BimmerBreaker]

For me, the additional water temp gage is to make sure that I have enough warning when the engine temp start to creep up, putting it in the block at the hottest section would make sense but that seems way too much work for now. So, seems like the putting the temp sender on the hot side of the thermostat housing is the next best choice. Although I like the idea of having another temp sensor to monitor the cooling system efficiency, but perhaps that's for another day.

Thanks guys.

If you want a warning, shouldnt you be monitoring the inlet? Monitoring the outlet seems like it would tell you of an overheat condition after it happened. Inlet, you could see that the "cool" coolant isnt as cool as it should be and catch it before it becomes an issue. I guess I just dont personally see the point to monitoring the outlet, but as long as it makes sense to you...

[Genes1s]

If you want a warning, shouldnt you be monitoring the inlet? Monitoring the outlet seems like it would tell you of an overheat condition after it happened. Inlet, you could see that the "cool" coolant isnt as cool as it should be and catch it before it becomes an issue. I guess I just dont personally see the point to monitoring the outlet, but as long as it makes sense to you...

If you monitor the inlet, you are monitoring how the cooling system "cools" the hot coolant, right? Lets just say, that the coolant reading in the inlet is high, technically it could be 2 things, the cooling system isn't capable/have issue or you have engine that is already overheated. IF you have an engine that is already overheated and you see the temp reading at the inlet of the T-Stat is 70C, the actual temp at the engine be will much higher (if the cooling system is OK). So, to me, this gives me false reading of the actual engine coolant temp in the engine.

If I'm reading it right after it comes out the engine, I have the best chance to catch the actual reading even though the overheating is already happening. The best chance to do this is actually on the cylinder head like how the factory does it but like I mentioned I don't have any spare plugs and not sure if I want to delete TB coolant hose.

Having both would be handy. You can find the delta and you can see how efficient your engine and your coolant system performing by comparing the temp before - after - before.

my 2 cents

[pbonsalb]

If my water pump failed, I would want to know sooner rather than later. The cold side of the radiator might be 20F colder than the hot side.

[M3C]

Always want to have the sensor closer to heat source so in case of overheating it will be detected sooner. I would constantly want to know what is the highest temp in the engine.