Plantoil/diesel conversion basics
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mcarman

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Reply with quote  #1 

exactly where does one cut into the heater hose for supply coolant and for return coolant on MB 1988 190d  2.5.  ??

danalinscott

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Reply with quote  #2 
Working from memory on this so check before cutting.

The heater hoses are a bit complex as a 12v circulating pump is incorporated into them. It is located on the firewall (engine side) center-top. Make sure it works or there may not be enough coolant circulated during low engine speeds. Having located THAT pump you will also have located one of the hoses you are looking for. The other hose is located beside/behind the oil filter. To determine which is the "to" heater and which is the "from" heater hose start the engine and hold onto both (you may need the help of a friend). The one which gets hot first is the "to" hose. This is the one you want to tee into to get hot coolant for the FPHE (and any other coolant heated components).  The other hose is of course the "from" hose that you want to send this coolant loop back to.

I believe that the "from hose" will be the one with the circulating pump. But...check before you cut. If it IS you may want to install the tee so the pump is "sucking" from this loop. Otherwise you may have very poor coolant circulation when the heater turns this pump on and causes most of the coolant to by pass the loop you are creating.

You may want to look at the schematics at: http://voconversionbasics.websitetoolbox.com/post?id=2273794 before you proceed so you better understand what you are trying to accomplish.



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mcarman

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Reply with quote  #3 

ok i've put the return between the 12v pump and car heater for additional sucking power as you suggested (i think).  no circulation to veg tank.  any ideas.

danalinscott

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Reply with quote  #4 
If the pump is not working it may block flow.
Are you sure the aux pump is working?

The first MB I ever worked on had one that had seized.

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alexmax021

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Reply with quote  #5 
Quote:
Originally Posted by danalinscott
Working from memory on this so check before cutting.

The heater hoses are a bit complex as a 12v circulating pump is incorporated into them. It is located on the firewall (engine side) center-top. Make sure it works or there may not be enough coolant circulated during low engine speeds. Having located THAT pump you will also have located one of the hoses you are looking for. The other hose is located beside/behind the oil filter. To determine which is the "to" heater and which is the "from" heater hose start the engine and hold onto both (you may need the help of a friend). The one which gets hot first is the "to" hose. This is the one you want to tee into to get hot coolant for the FPHE (and any other coolant heated components).  The other hose is of course the "from" hose that you want to send this coolant loop back to.

I believe that the "from hose" will be the one with the circulating pump. But...check before you cut. If it IS you may want to install the tee so the pump is "sucking" from this loop. Otherwise you may have very poor coolant circulation when the heater turns this pump on and causes most of the coolant to by pass the loop you are creating.

You may want to look at the schematics at: http://voconversionbasics.websitetoolbox.com/post?id=2273794 before you proceed so you better understand what you are trying to accomplish.



Thanks for sharing.




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danalinscott

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Reply with quote  #6 
Quote:
as of yet I do not really understand the coolant diagrams


I assume you mean the diagrams in this link.
http://voconversionbasics.websitetoolbox.com/post?id=2273794

It is simpler if you discuss coolant configurations in that discussion.

Quote:
I like the “r davis in VA” concept of avoiding endangerment to your coolant system by way of FPHE to create a parallel coolant loop.

Quote:
any of the coolant diagrams describe the secondary circuit I wish to use- a fphe passes heat to a separate coolant system dedicated to heating the wvo.  The primary engine cooing system is thereby isolated from the heightened possibility of exposure of engine overheating due to hose failure/trauma.


I have never heard of a completely seperate coolant loop being used. It would appear to add complexity and cost without much in the way of benefits. The few times I have heard of coolant loss being a problem has been in off road use. If you can provide a link to a discussion or description of that I may be able to help you sort it out.

Most folks use a circuit like this

but since the coolant flow on a Mercedes can be so low at idle an aux coolant pump (like the one used for cab heater coolant circuits on MBs) is incorporated.

Quote:
I already bought two 30 plate fphe’s from omar- one to heat the veg oil and one to make the 2nd coolant circuit 


30 plate FPHEs are usually considered overkill. A single 16 or 20 plate FPHE is more than sufficient. More plates do not mean more heat transfer at the flows and temps in a VO conversion. The vendor didn't suggest that you buy two 30 plate FPHEs did he?

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danalinscott

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Reply with quote  #7 
How can I put this delicately...
The guide you provided a link to is based on really outdated and in some cases very bad information based on a poor understanding of the issues.

It also appears to be slightly geared to selling components that are either unneccesary or marginally effective..at higher than average prices.

If you are planning on basing your conversion on the information there prepare to pay two times as much for a conversion that is half as good a you can do with a little bit of research yourself.

Sorry if that sounds harsh.

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danalinscott

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Reply with quote  #8 
Quote:
  but I do not, as yet, see any short side of containing the pressurized engine coolant as one system and running another back to the wvo tank.  perhaps a bit of heat loss, and the expense


Quote:
And if it is just me being idiosyncratic then hey that's me. 


It is out of the box and new perspectives from which new..and sometimes better concepts come. In this case it seems to be an old idea that didn't work out as well as originally hoped for which simpler, less expensive, better solutions have been developed.

Normally I would not advise someone who has not done a few conversions to try something so different..but in the end that is up to you.

I would expect such a system to take significantly longer to warm up compared to a more conventional configuration. And if I recall correctly that was one of your original concerns. The large FPHES will also slow this a bit as well.

It is pretty easy to either run your coolant/VO lines so they cannot be easily breached by road debris or shield them. This is actually what most folks do.

What I am saying is that there are several significant drawbacks to the design and no real advantages. But again..if you want to do use this configuration and those massive FPHES...it is your perogative.

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