1985 300TDT - Why do I really need a heater in Hawaii anyway? Especially in the summer! I can plug ends where they enter firewall - Change core when I get the nerve. Does anyone know which hose(s) go into core and which hose(s) come out? (Water flow that is) There are 3 total going through firewall - that's what it looks like. Thanks.

Smartin,

Why don't you try some "Bar's Leaks" or other sealer first? And try leaving radiator cap loose to reduce the pressure.

I thought you determined that the leak was out side of the heater core/AC air box which meant is was not the heater core.

Sorry, I don't know anything about the 3 water connections going thru the firewall. My car had only 2.

P E H

PEH - Its a pretty good leak - by 1:00 p.m. third of reserve (plastic) tank is gone. I'm not sure but I think the previous owner had something in there once before? Chalky brown color substance - dries whitish tan color. But I am open to ideas - You say Bars is about the best? Thanks

Smartin,

Yes. I believe Bar's is as good or better than any. Have you let radiator cap loose to eliminate pressure? That will slow leak immensely.

The only trouble with disconnecting heater core is your defroster might not work well. But maybe you don't need that there either.

P E H

I remember personally seeing new economy cars sold in Hawaii in the early '70's delivered with no heater at all. Whether that was common practice or a "delete" option, I don't know. I like the bypass idea better than a "stop leak" product (goes into entire cooling system and may plug something you don't want it to). With some plumbing fittings you should be able to rig a simple bypass and replace heater core at your leisure (when forced to do something else requiring dash/console disassembly ). If you just plug it, you may want to disconnect the electrical to the auxilliary water pump?

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

I am with Jbaj007 on this ..... if you have any stuff partially clogging any radiator tubes, for instance, it treats them as if it were a leak...so you can get overheating when you had none before... use the bypass system to avoid that... or get up the nerve and instructions to open up the dash and fix it....

I pulled the heater core out of my 81 300D parts car last winter. If your TD is the same as that one you would need to pull the dask pad to get to it. Then there are plenty of wires and cables to mess with after you get the dash pad off. Not a difficult technical job, but it is a knuckle scraper.
Perhaps better to just plug the heater lines.

Thanks for ALL the replies! Is aux pump for heater core ONLY? If I plug hoses where they go through firewall, do I need to eliminate aux pump? I f just BYPASS - does anyone know which hoses ENTER core and which hoses EXIT core? Thanks.

I can't believe nobody has answered this. Does your car have dual zone climate control? If so then there are probably two entering and one leaving, or one entering and two leaving. In either case, you would need a 3-way fitting to tie them all together in order to completely eliminate the heater. Note: this is all my ASSUMPTION. But it keeps the thread alive and hopefully somebody will confirm or correct it with facts.

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Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References

Rick - I guess all good minds think alike - just thought about that again late last night, 3 way is really all that is necessary, then I wont have to worry about aux pump. I think aluminum would be the best. Or other material? Thanks.

Copper fittings in various combos are readily available at all hardware stores and have a good history in mobile coolant systems. Wouldn't really worry about galvanism in a fairly isolated spot like you're doing. The reason I mentioned disconnecting the aux. water pump if you bypass/plug the heater, is that it is only used for idle speed cabin heating and on the off chance that it would fail it can use the climate control unit as it's "fuse".

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)

Looks like a successful by-pass! The hose from engine (near oil filter) that went on fitting into firewall - I just reconnected it to the pipe that comes from the aux pump - disconnected before "y" that feeds 2 hoses into firewall - connected right at that point near oil filter USING SAME HOSE! Will have to closely monitor it - no leaks yet and no more drips inside car. Thanks to all. Also - finally fixed leak for hydraulic levelling system - it works now - I put in a temporary rubber hydraulic rated hose with clamps (low pressure return side) and adjusted valve control - it works like a charm now! Again thanks to all and thanks for this forum. Steve

Bypassed heater core using original hose from engine side near oil filter. Success! Thanks to all.