odd coolant leak

[BCMike]

Comin' home tonight the coolant level light came on. Bummer! At least the engine temp was still normal. So I pulled off and popped the hood to find a stream of coolant"pissing" out from a gasket between a plate that mounts to the front side of the throttle body. My first thought is "What's coolant doing running up there!?". Lo and behold, there is a cooling hose running from the thermostat housing to the throttle body.

So my questions are: anybody have a part number or good way to describe this blown gasket between the aforementioned plate and throttle body to my local dealer and what are folks opinions on coolants?

[Bozo325]

Throttle body heater ? My Bentley manual points it out, but doesn't mention it by name... I read that some folks simply block the hoses to it off if they live in warm climates.

BMW specifies phosphate-free antifreeze. This avoids clogging of the radiator by AluminumPhosphate deposits that can develop when phosphate based anti-freeze begins to break down under heat.

I use the new extended-life 'Dex-Cool' spec stuff.
No phosphates.

[BCMike]

Thanks for the coolant perspective Bozo. I'll spring for a gallon of the dealer's brand when I pick up the gasket. While it's still plenty warm here in greater Vancouver (spot-on perfect in fact :), cool wet winter will come and the word on the street is that the throttle valve much prefers to be warm, so a repair is in the cards.

[SilverE30]

That actually just happened to me. I believe it's called the coolant bypass gasket. It's like 85 cents and should be a stright forward replacement. The only thing you really need to watch out for is the screws holding the "waterblock" on place since they are a star pattern (torx?). I picked up hex replacements at Menards and replaced all the hardware as well since one was frozen and needed to be cut off. Good luck.

[BCMike]

Well Canadian dealers gouge a bit more than those south of the 49th but, the repair was a piece of cake except for the lower in-board bolt that is a little tought to get to due to the intake manifold and the long tube that receives the PCV hose. A short Torx head and a small crescent wrench ended up being my solution.

$2.65 Canadian gets the gasket, but of course the PCV hose was egg shell brittle. I should have figured since I'd already replaced the fuel line to the rail that also runs under the intake mani. That hose fetched $18.75! That, about a half gallon of coolant and a good hose-down of the engine compartment to rinse off the antifreezed "pissed" all over the place and my l'ilredcar was on the road again with still plenty of time left for Saturday's Honey Do list. Thanks to all. These forums are great for DIYers new to bimmers to kick things around a bit before diving in.

[M3 Mario]

I just pulled the hoses off and routed them back in, the reason for it is to keep air from freezing when going into the motor. No point in it, I've ran it without any problems.

Just imagine how hot it gets in the summer, kind of cancels out the purpose of a CAI.

[Anetsberger]

Originally posted by M3 Mario
I just pulled the hoses off and routed them back in, the reason for it is to keep air from freezing when going into the motor. No point in it, I've ran it without any problems.

Just imagine how hot it gets in the summer, kind of cancels out the purpose of a CAI.

I don't believe that is the purpose. On my E30 there is a block of aluminum between the intake plenum and the throttle body. The intake plenum can reach temperatures much higher than the engine coolant temperature. The block of aluminum's temp is kept stable by the engine coolant that flows through it and prevents excess heat from the plenum from reaching the throttle body. If the throttle body were to be heated, the materials would expand at an uneven rate and air leaks would develope between the throttle plates and housing. This is a crucial component and should not be bypassed.

Tom

[BCMike]

Tom,

I thought this thread had died. Great to get your opinion. It intuitively makes more sense. The "throttle body heater" could never heat the throttle body when the engine is cold because the thermostat is closed and the coolant in the hoses start out at about ambient temp. Once the engine starts the intake manifold heats rapidly and would, as you describe, transfer alot of thermal units to the throttle body which is designed with aluminum, brass and steal components that have different expansion properties. The devise must work as a "throttle body thermoregulator".

[Anetsberger]

Hmm, I didn't know the thread had died. I guess I just jumped in at the end. But yes, I feel you have the idea.