Help request regarding m42 coolant hoses

[Simon S]

Apologies if this is posted elsewhere. I’ve researched this site, m42 club, and Bentley manual..

the question is specific to the two coolant hoses that connect to the fittings on the firewall (engine bay side).
The old hoses that I removed appear to have a ‘jumper’ hose between the two – along with some contraption (bypass valve?) that I cannot locate on realOEM, Bentley, etc. When I compare the old hoses to new replacement hoses, it looks like someone spliced the hoses to incorporate the jumper/bypass set up.

I’m doing a throttle body heater plate delete – and want to know if it’s acceptable to delete the jumper/bypass stuff also. What’s its purpose?

All this is/was connected together. Crazy!!


Reference shots of old and new hoses:




The thinner hose, T-intersection, and contraption are what I'm curious about removing:



Thanks for any input or help on this..

[fiftytakedowns]

im pretty sure you can just cap it off

look up the mess under the intake in m42club

[Simon S]

look up the mess under the intake in m42club

unless i missed something, I've been all over several of the 'intake mess' threads on m42club and didn't see any mention of this jumper/bypass stuff - most of them relate to deleting the throttle body heater plate plumbing..

in one thread (TB heater delete), i *think* i see where the jumper stuff is there


in another thread (just replacing hoses), i'm not seeing the jumper/bypass hose


it's hard to see it (or not see it?) in posted pics because the shit is/was nested under the ICV, between the engine and firewall, and hidden behind the wiring harness,lower intake runners, and vacuum hoses.

i'm leaning toward leaving it out - just don't want to be doing something wrong..

[Simon S]

screw it. realOEM is showing no trace of it. The jumper/bypass/superfluous hose shit is getting deleted along with the heater plate crap.

[stegosaurus]

I had the same problem doing my hoses up after the head gasket. Unfortunately I didn't take pictures and I don't have much of an idea of how I ended up putting things together, but it worked.

If you don't figure it out, send me a pm and I'll see about getting some pictures for you, I ended up pulling info from a bunch of different threads on m42club and realoem to get something that seemed alright.

It's really a fly by the seat of your pants job with these hoses, I know at least that I wasn't more than 80% confident that I had it done right.

[FredK]

That is a coolant bypass valve that was installed during a still active recall campaign, to reduce the likelihood the heater core will rupture from system overpressurization (hot days, heavy load, etc.).

Someone posted a story of how during a DE or club race, that his friend's leg got burned badly from the heater core rupturing just a few weeks ago. In any case, if you are going to delete the heater core in your car, there's no reason to run this valve.

[tjts1]

M42 cooling system is bat shit crazy.

[Simon S]

That is a coolant bypass valve that was installed during a still active recall campaign, to reduce the likelihood the heater core will rupture from system overpressurization (hot days, heavy load, etc.).

Someone posted a story of how during a DE or club race, that his friend's leg got burned badly from the heater core rupturing just a few weeks ago. In any case, if you are going to delete the heater core in your car, there's no reason to run this valve.

cool. Thanks for providing some insight.
Incidently, I just now found the related hoses/parts on realOEM

[stegosaurus]

If you're still having a problem with the hoses send me a pm. I think I still have the receipt with all the part numbers from the order I made (I ordered all the hoses).

[Simon S]

If you're still having a problem with the hoses send me a pm. I think I still have the receipt with all the part numbers from the order I made (I ordered all the hoses).

no problems as yet. Thanks for your offer.

The hose work went pretty smooth. Researching and using my head a bit made the process straight-forward.

It appears that I traded having more simplistic coolant routing for what may be a slight risk of steam-burning my legs at some time. Because I've never heard of this ocurrance until now - and given the car's age and miles (~130K), I'll take that risk and also proactively swap in a new heater core w/in two years or so.

Unless more people speak of not having those hoses as being a hazard, I say fuck those extra hoses. Fuck them hard.

[3bvert]

yes it was a recall thing , I was told, but not all cars got it

for instance, my 1991 318 IS did not have it ( its a parts car now)
my 91 318IC did have it.. Note, same year, same engine, same heater core design and valve, one month apart on build dates
when I deleated my throttle body crap, I got rid of them too... too me it was just another place for something to go wrong. the original heater core did not leak in the sedan, the one in the vert I just replaced. I do not think it had anything to do with the elimination of thta gizmo, but the 19 years of age and poor maintanince by the p.o.

it is the same heater core used for many bmw's, including 325's and M3's up to and including 91. I would think if there was an issue wiht heater cores blowing apart, we would hear more about it
and think of all those bigger engines used in popular swaps, are they restricitn g water flow to the heater ?
unless those cars dont put out the water pressure our M42's do or have other ways to restrict pressure

pelican only sells the hose that does not use it and they sell the behr heater core. ( original equipment) I guess, Ive been told, that there are inferior ones out there like on e-bay, but I did not want to mess around. when it comes time to do your heater core, dont forget your o-rings, they dont come wiht the new core.