Heater core deletion and coolant redirection

[Creesic]

The engine I have going into my swap is a NV M50 from an E36. The hose connected to the back side of the head (driver side) that then flows to the heater core was bad, and this is what it looks like. I'm talking about the first hose that then splits to the other two. It had a hole.

coolant.jpgcoolant 2.jpg

This doesn't look anything like what you find on realoem, so before I had checked, I was wandering around my garage looking for something like this I had pulled off of my factory motor. Obviously, I didn't find anything.

I had a friend with me though, and he brought up the idea to buy this.

It seemed like an okay idea. I live in Florida, so I don't need the heat, so why not just delete the heater core?

--- I'm not sure how coolant flows through the head there, so I'm not sure if it's a good idea just to cap it off. If capping it is fine, then whatever, but would it be a better idea to plumb it to a return?

[Layne]

It doesn't make a bit of difference if you block it or return it, that's the same thing as turning the heater on or off. The engine does not care.

It's not a very good idea though. Even in Florida you'll need to defrost the windshield occasionally.

[Creesic]

Maybe I didn't clarify. If I block it where coolant exits the head, then where does that flow go? Does it just sit there? never being able to reach the radiator? And if that's the case, should I just hook it up to a return line?

I've only had to defrost three or four times this winter, so it's next to useless. That's how it is every winter.

[gearheadE30]

Heater core blockoffs are for race cars....and even then, I leave the heater cores in mine for defog and cooler days. I'm more of a fix it right and be done with it kind of person, especially when the fix is not difficult. Also makes reselling the car a lot easier, if you ever want to do so. Just buy the correct heater core hose for a ~8/1992 production date 525i, which would have been an M50 non-VANOS as well, and you'll be good to go. 10/1992 was when production switched to the M50TU, but I think it uses the same heater hose. I just replaced all the hoses in mine; I think it was less than $100 to do all the coolant hoses in the engine bay.

That piece that you pulled off of the E36 was the result of a TSB that affected E30s as well - the plastic heater core end caps would become brittle over time, and if the car overheated (more pressure in the cooling system), there was a chance for the heater core to explode, dumping 200+ degree F coolant on the driver's feet and legs. That bit with the 3 fittings on it is a small thermostat that would bypass the heater core in the event of overheating, reducing pressure and the chance of explosion. Personally, if you maintain your car and keep an eye on coolant temp, I would not worry about reinstalling that mess of hoses. Also, E34 cores are mounted differently and will drain the coolant under the carpet rather than onto your feet, so there's less risk anyway.

And to your third question about coolant flow, I believe the flow path of the coolant in an M50 is from the water pump through the block towards the back of the engine, then up into the head, then towards the front of the engine and out the front past the thermostat. It's more of a U-shape than the straight line most people think of. The heater core inlet line coming off the back of the head picks up coolant that has been heated by the block, but that has not yet gone through the head. Blocking this off has no impact on coolant flow performance in the block.

[Creesic]

I'm more of a fix it right and be done with it kind of person, especially when the fix is not difficult. Also makes reselling the car a lot easier, if you ever want to do so.

I am too, though I also hate clutter and adding weight. I also plan on never selling this car either, so there's that.

Blocking this off has no impact on coolant flow performance in the block.

Good. Noted. Now the only reason not to do this is to defrost my windshield. I can totally just remove the core, reduce weight, reduce clutter, and potentially save my interior from boiling coolant leakage... But I think I may have purchased that one line to the heater core anyways, so if that's the case, it'll remain stock.

[EX27]

any updates of what you did ? I'm doing the same thing...