Simon's take on: 'Mess Under the Intake'

[Vivek]

The idea that hardware store doodads and driveway engineering can somehow out-smart the Germans seems hilarious to me. If you'd like to bypass the TB heaters you can do so with the existing factory hoses.

Simply replace what's leaking, leave what's not, and enjoy the factory drivable experience.

There's almost no reason to have a heater plate on the throttle body.

[M3Philipp]

There's almost no reason to have a heater plate on the throttle body.

What is the reason for the throttle body heater plate?
I think I have asked before, but simply I did forget it.
And by the way, I have never seen an 318is here in Germany, that uses or has the heater plate from stock.
While at the same time, many US 318is seem to have it.

[roguetoaster]

I suspect the idea was to raise intake temperatures for emissions compliance. Perhaps it has to do with prolonging the life of the catalytic converter or heating it up faster since most European M42s did not have them.

I think I have read elsewhere that it was to prevent icing, which I don't think it correct as the coolant would be cold and as you say European M42s don't have the system.

There was also a similar feature on my 16v swapped GTI, except it was a temperature controlled switch that moved a plate in the filter box causing air to be drawn from the engine bay instead of the snorkel/outside air system.

[bats]

Great write up Simon.

I'm wondering about the Heater Core hoses.

23 1 64211386691 Return hose (from core) 27.84 27.84
24 1 64211386690 Inlet hose (to core) 21.88 21.88

Do these hoses eliminate the need for the bypass valve (for the Heater Core)?

[Simon S]

Great write up Simon.
I'm wondering about the Heater Core hoses.
Do these hoses eliminate the need for the bypass valve (for the Heater Core)?

Thanks.
The bypass valve and associated bypass valve hoses are spliced into the stock heater core hoses.

To answer your question, new heater core hoses do not “eliminate the need”. The choice to install a bypass valve is up to you.

Per answers given in this thread, the bypass valve is a thermostat that closes off flow to the heater core in the event of elevated coolant temperatures. If you’re not worried about overheating your engine/coolant system, then I wouldn’t worry about installing the bypass.



If you get new heater core hoses, install them as is to eliminate bypass valve - or cut them in appropriate spots to incorporate bypass valve.

Fwiw, here's a RealOEM link to the "thermostat"/bypass valve parts and plumbing:

http://www.realoem.com/bmw/showparts.do?model=AF93&mospid=47305&btnr=64_0135&hg=64&fg=99

[unevolved]

Why would the bypass close off the heater core if the engine's overheating? Wouldn't you want as much heat transfer as possible?

When I used to work at a driving school in college, the only way we could get the Miatas to stay below about 215F was to run the heater when it was real hot out.

[Simon S]

Why would the bypass close off the heater core if the engine's overheating? Wouldn't you want as much heat transfer as possible?

Ha. Good point.
The way I understand it - the heater core/valve under the dash can be a weak point over time.
When it fails, coolant may spew into cabin and on the driver’s leg.
I believe the ultimate purpose of the bypass valve is to prevent a core/valve failure w/in the cabin.

[bats]

Thanks.
The bypass valve and associated bypass valve hoses are spliced into the stock heater core hoses.

To answer your question, new heater core hoses do not “eliminate the need”. The choice to install a bypass valve is up to you.

Per answers given in this thread, the bypass valve is a thermostat that closes off flow to the heater core in the event of elevated coolant temperatures. If you’re not worried about overheating your engine/coolant system, then I wouldn’t worry about installing the bypass.



If you get new heater core hoses, install them as is to eliminate bypass valve - or cut them in appropriate spots to incorporate bypass valve.

Fwiw, here's a RealOEM link to the "thermostat"/bypass valve parts and plumbing:
http://www.realoem.com/bmw/showparts...35&hg=64&fg=99

Thanks, I ended up figuring out the reason hot coolant was not flowing was because the bypass valve was blocked (old cruddy coolant) beyond repair. Purchased a new one and voila, I have heat in the vents.

[djmossm42]

What is the reason for the throttle body heater plate?
I think I have asked before, but simply I did forget it.
And by the way, I have never seen an 318is here in Germany, that uses or has the heater plate from stock.
While at the same time, many US 318is seem to have it.

Here's the recall notice for the TB from my insurance

Recall Number: 91V219000
Dates Manufactured: JUN 1990 to NOV 1991
Number of Vehicles Affected: 15200
Date Owners Notified On: JAN 0001
THE CRANKCASE VENTILATION SYSTEM, VENTED INTO THE INTAKE TRACT OF THE ENGINE AT THE BELLOWS BOOT AHEAD OF THE THROTTLE HOUSING, ALLOWS WARM WATER VAPOR FROM THE CRANKCASE VENT TO CONDENSE AND FREEZE IN THE COLDER BELLOWS BOOT WHEN THE AMBIENT AIR TEMPERATURE IS 15 DEGREES FAHRENHEIT OR LESS. THE BUILD UP OF ICE CAN DISLODGE AND MOVE INTO THE THROTTLE HOUSING, PREVENTING THE THROTTLE PLATE FROM FULLY CLOSING WHEN THE DRIVER RELEASES THE GAS PEDAL.
Consequence of Defect:
IF THE THROTTLE PLATE IS PREVENTED FROM CLOSING, THEREIS AN INCREASE IN IDLE SPEED AS WELL AS SLOWER THAN NORMAL DECELERATION, WHICHOCCURS WITHOUT PRIOR WARNING AND COULD RESULT IN AN ACCIDENT.
Corrective Action:
REPLACE THE THROTTLE HOUSING WITH A VERSION CONTAINING A MODIFIED HEATING SYSTEM ALONG WITH REROUTING OF THE CVS HOSE. THIS WILL PREVENT ICE BUILD-UP IN THE INTAKE TRACT.

So if you don't live in an area or travel to places that reach below-freezing temps removing it is fine.

Heres' the recall for the Heater Core

Recall Number: 93V015000
Dates Manufactured: JAN 1983 to JAN 1993
Number of Vehicles Affected: 375000
Date Owners Notified On: JAN 0001
THE MALFUNCTION OR FAILURE OF A COOLANT SYSTEM COMPONENT RESULTS IN SIGNIFICANTLY INCREASED COOLANT TEMPERATURE AND A RESULTING INCREASE IN SYSTEM PRESSURE.
Consequence of Defect:
VEHICLES OPERATED UNDER THIS INCREASED COOLING SYSTEMPRESSURE CONDITION CAN SUFFER DAMAGE OR FAILURE OF PARTS OF THE COOLING SYSTEMSUCH AS (1) LEAKAGE FROM A COOLANT HOSE, (2) LEAKAGE OF THE RADIATOR OREXPANSION TANK, (3) DISCONNECTION OF A HOSE FROM A PIPE OR A FITTING, AND (4)CRACKS IN THE HEATER CORE END PIECE RESULTING IN COOLANT LEAKAGE. IN SOME CASES,BOILING COOLANT CAN CONTACT THE LOWER RIGHT LEG OF THE DRIVER RESULTING INBURNS. ALSO, ESCAPING COOLANT IN THE PASSENGER COMPARTMENT CAN CAUSE VAPORFOGGING OF THE INTERIOR SURFACE OF THE WINDOWS, REDUCING DRIVER VISIBILITY.
Corrective Action:
DEALERS WILL INSTALL A THERMOSTATIC BYPASS VALVE IN THE ENGINE COMPARTMENT TO CONTROL COOLANT TEMPERATURE IN THE HEATER CORE. ALSO, A NEW DESIGN RADIATOR CAP WILL BE INSTALLED, TO CONTROL PRESSURE AND PROVIDE GREATER COOLANT OVERFLOW IN THE EVENT OF OVERHEATING.

[Simon S]

Cool.
Thanks for that contribution. Good stuff !

[bsturman92]

hey guys. so i had just ordered all the parts needed to do the mess. now i have one quick question... i want to do silicone hoses for all my vacuum lines because i dont wanna risk any hoses collapsing.. do you think this would be a good idea? any help is appreciated

[Simon S]

meh.
Like you could and all but it's just a whole lot easier to buy/use OE parts since they're all pre-shaped.
It's not like I worry about them ever collapsing..

[unevolved]

Yeah, I mean, it won't hurt, but it isn't exactly necessary.

[bmwman91]

The hoses won't collapse. They crack & give you awesome vacuum leaks to chase, but they don't collapse lol.

[bsturman92]

really? i was doin alot of reasearch on m42club and e30tech and heard if a few people having there hoses collapse on them. idk if they were using weak or improper hoses or what but i thought i would ask before i went ahead and ordered it all... but i had just got 5 feet of silicone vacuum hose from a customer of mine who has his own shop! so i guess im going that route. cant hurt and shit it was free.... no complaining here! but now i cant decide whether or not i want to delete all the coolant relief hoses or not. that picture you posted of urs simon looks clean AF. i love it. but f$%* having a chance of hot coolant spilling on my leg.... im not tryin to bring up that discussion for everyone to have again but i really wanna get rid of em just because of how clean it looks lol