Tap coolant from cabin heater return line? BMW 525

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Tap coolant from cabin heater return line? BMW 525

Postby Remo » Sat Sep 29, 2012 6:05 pm

Hello!

I have read and learned a lot on this forum, and I have finally completed my conversion on a 95 BMW 525 tds.

I have a huge problem understanding where and how I should tap into the coolant system. I've understood that I should use the cabin heater circuit, however, the supply line for the heater is buried deep below the intake manifold. This would be a massive job for me the remove. Also, If I tee in there, I'm also worried the the connectors will get in the way of the intake.

Therefore, I'm wondering if its okay to use the heater return line, which is very accessible and also close to my wvo components (FPHE, heated filter, H-I-H, tank coil).
Below is a picture showing the return line.

I have some questions I'm hoping you experts can help me with. Here in this part of Europe its getting very cold right now.

1. Would it be okay using the return line? (seeing that the supply line is more or less out of the question)

2. I see that forum members recommend parallel circiut, one for FPHE and one for the rest. How do I go about using a parallel setup when everything connected to the same pipe?

3. Should I route all coolant from the heater through my wvo circuits? Meaning not t-eed off, but rather cut off, into wvo and then back? But wouldn't that make it series, not parallel? I'm confused :roll: Just afraid that I won't get enough flow if I t-eed it off, since they're all in the same pipe? Perhaps t-ees with ball valve after them, so I can restrict flow going back to the coolant pump.

4. The overflow tank is originally t-eed into this line, should I connect the wvo parallel circuits before or after the tank, or does it matter?

Thanks for your time and help.
Image
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Re: Tap coolant from cabin heater return line? BMW 525

Postby John Galt » Sun Sep 30, 2012 12:43 am

If it was my vehicle I would insert two tees into the heater supply line anywhere between the engine block and the heater. One tee would feed the FPHE and the other would feed all the other VO heaters. The return from the FPHE and the return from the other VO heaters would connect to the heater return line.


╔=coolant pump====╗
╠=cab heater======╣
╠=FPHE ==========╣
╚=HOH+filter+etc===╝

Image

all the other VO heaters in a parallel loop

Image
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Re: Tap coolant from cabin heater return line? BMW 525

Postby Remo » Sun Sep 30, 2012 2:24 am

Hello John,

Thank you very much for your input. Given the problems I have with the supply line, what would you suggest I do regards to connecting to the return line?
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Re: Tap coolant from cabin heater return line? BMW 525

Postby SunWizard » Sun Sep 30, 2012 9:06 am

The return line is not good. There must be a place in the supply line between the engine and heater core, even if its at the firewall.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Re: Tap coolant from cabin heater return line? BMW 525

Postby Remo » Sun Sep 30, 2012 1:16 pm

Great, thanks for your input.

I've then decided to remove the intake manifold so that I can connect to the heater supply line. I'm planning to use a Y-connector since the direction will get me better flow than a T, and add a ball valve to restrain the flow to the heater. (the ball valve will be a bit inaccessible behind the intake, but I think it will do).

I'm also adding a 230 volt coolant heater with a build in circulation pump, so that my coolant is hot when I leave home in the morning.

Will it be okay the put the circulation heater in the return line of my wvo coolant lines, as long as the flow direction is correct? Flow direction does perhaps not matter either, since it only circulates when the car is plugged in, i.e not in use.

Do I need to put the wvo coolant return before or after the expansion tank, or does it matter? Ref. picture above.

Thank you very much. About -2 degrees Celsius here, better get this job done next weekend.
Remo
 
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Re: Tap coolant from cabin heater return line? BMW 525

Postby SunWizard » Sun Sep 30, 2012 7:02 pm

Remo wrote:Will it be okay the put the circulation heater in the return line of my wvo coolant lines, as long as the flow direction is correct? Flow direction does perhaps not matter either, since it only circulates when the car is plugged in, i.e not in use.

Should be OK. You want it where it will heat the block the best, that is the big mass that needs to be hot before switching to WVO. That is why most block heaters are inside the block and don't circulate. Try to avoid circulating to the radiator or heater core or other places which just lose the heat.
Do I need to put the wvo coolant return before or after the expansion tank, or does it matter? Ref. picture above.

It shouldn't matter if the expansion tank is simply tee'd off the line as most I have seen.
YVORMV - Your veg. oil results may vary.
95 Dodge Cummins 4x4 SVO WVO conversion.
81 Mercedes 300D- stock and happy on V80/D20 blend.
Low fossil net zero house- 100% solar power and heat.
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Re: Tap coolant from cabin heater return line? BMW 525

Postby John Galt » Sun Sep 30, 2012 7:29 pm

Given the problems I have with the supply line, what would you suggest I do regards to connecting to the return line?
The return from the VO heating can tie into the return line to the coolant pump.

I agree with what wiz said about the other points.

It's supposed to go to -5°C overnight here, so I know what you mean about getting things done before it's below freezing 24/7
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Re: Tap coolant from cabin heater return line? BMW 525

Postby Remo » Thu Oct 04, 2012 2:38 am

Followed your advise and changed my setup last night. Removed the intake and put a Y-connector and a ball valve into the heater supply line. Then, from this line that goes to the FPHE, I T-eed off to create a parallell circuit for the heater filter, HIH and tank. Couldn't t-ee both circuits off the same heater supply hose (wasn't enough space) so therefore I did it this way.

This really makes a huge differance. My temps quickly rises to 140-150 degrees fahrenheit, and stays there more or less. I rises to around 160 on idle, but cools down when I hit the highway. I guess this is because of the radiator cooling the whole system down?

I'm planning to do even more modification this evening; putting in a coolant aux pump on the return line to help with the flow and insulating the FPHE, filter and fuel lines. The outside tempetures here are on average on about 45 degrees F.
Its going to get below 0 fahrenheit in the winter time, so I was hoping for steady temps a little higher right now? What do you think? If I have 140-150 now, would the temps keep around the same when the outside temps drops? Switchover time would increase but..

Here's a few pictures of my setup:
Image
Image
Remo
 
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Re: Tap coolant from cabin heater return line? BMW 525

Postby John Galt » Thu Oct 04, 2012 2:22 pm

I guess this is because of the radiator cooling the whole system down?
If the coolant thermostat is working correctly the radiator shouldn't cool the block. Insulating the FPHE and 'downstream' lines will increase temps.
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Re: Tap coolant from cabin heater return line? BMW 525

Postby Remo » Thu Oct 04, 2012 3:58 pm

Thanks John.

Insulated the FPHE with 10 mm thick insulation, and I used pipe insulation for the oil lines and some of the coolant lines.

Now, my oil temp is steady at 160 degrees Fahrenheit! I also added the aux coolant pump so that probably helped a little also.

I'm very pleased, and happy that I'm finally more or less completely done with my conversion. I took a lot longer than expected, but now that I'm done, I think I could have done the same job over again more than twice as fast.

The best tip you guys gave me that really made the difference was tapping out of the heater supply line and creating flow by connect the return to the heater return line.
Remo
 
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