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Old 02-14-2012, 02:45 PM   #1 (permalink)
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Default Throttle body heater plate bypass - why?

On my 2000 Disco the previous owner disconnected the hoses from the throttle body heater plate and connected them together with a 90 deg fitting. Before I restore them to their original position is there maybe a clever reason this might be done? Such as I live in Florida and don't need the extra heat or something?
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Old 02-14-2012, 03:00 PM   #2 (permalink)
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The reason this is done is because the fittings leak where they go into the throttle body. I had this exact thing on my DI and when I connected them back to their appropriate positions I couldn't get the leaks to stop (in fact they're leaking on my DII, but not very badly). I removed the intake chamber and tried to rebuild the fittings, but they wouldn't seal for very long. The problem is the fittings are brass? and they're mated into aluminum which has a very different coefficient of thermal expansion...as the engine goes through its normal daily heat cycles, the aluminum eventually breaks the fittings free no matter what method I tried to attach them together.

The purpose of the coolant flowing through the throttle body is to allow the engine rpm to drop once the engine reaches operating temperature. There's an air valve with a heat-activated spring behind it which opens up when it gets warm. With it bypassed, I had to turn the idle way down on my engine.
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Old 02-14-2012, 03:43 PM   #3 (permalink)
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The t/body pre-heater has nothing to do with allowing the idle to drop back down at operating temp.
Mine has been by-passed for 9 years, t/body never froze up and idles drops down as it should without any adjustment of the factory set idle.
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Old 02-14-2012, 05:04 PM   #4 (permalink)
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The heater, like Mike said, is to prevent ice from forming in the throttle body. When the air rushes through and cools it could become cold enough to freeze. And stick the throttle open. There's a simlar carb heater on piston aircraft engine for a similar reason. In this case it's the carb that freezes and cuts off airflow. It uses warm air since aircraft engines aren't water cooled. Some people have had them bypassed for years and some have had them freeze and stick open. I would think that cool temps are less prone to icing in the throttle body than moisture in the air itself but have heard of them freezing in cold dry air. Bottom line. It's a mixed bag. Mine isn't bypassed but it's leaking. Again.


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Old 02-15-2012, 05:15 AM   #5 (permalink)
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I thought the throttle heater was overkill.

I got a bad TB leak last summer very far from civilization. Managed to return home by-passing it. When I got the replacement parts, I couldn't remove two of the tiny screws that snapped flush in the alu body, so I left it by-passed and forgot about it.

Here in the Québec eastern township temperature will often drop below 20 deg C. Each time this happens, the throttle will freeze on the highway. Tried to lube the mechanism many times but it will always stick in the next cold weather. Of course it freezes only at high speed.

Not easy to manage on an automatic vehicle with lousy brakes.

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Old 02-15-2012, 08:01 AM   #6 (permalink)
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These are what throttle body heater plate looks like (in case someone wonders).

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Old 02-15-2012, 11:17 AM   #7 (permalink)
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they must have removed the low-idle valve on the newer engines. There were instructions in the rave manual about sticking your finger in the hole to verify the engine idle increases in order to check the functionality of the valve. That was the only way I knew what it was supposed to do on my old DI.

But if it's just a de-icer now I might just go ahead and bypass mine since it's leaking a little.
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Old 02-15-2012, 11:43 AM   #8 (permalink)
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Like Disco Mike my throttle always dropped after a few minutes.
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Old 02-15-2012, 12:14 PM   #9 (permalink)
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Because your truck lacks the fictional part known as the "low idle valve"! My truck also lacks it, as do all other Discos that were not factory equipped with the unicorn package.
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Old 02-15-2012, 02:27 PM   #10 (permalink)
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Quote:
Originally Posted by harralk View Post
The reason this is done is because the fittings leak where they go into the throttle body. I had this exact thing on my DI and when I connected them back to their appropriate positions I couldn't get the leaks to stop (in fact they're leaking on my DII, but not very badly). I removed the intake chamber and tried to rebuild the fittings, but they wouldn't seal for very long. The problem is the fittings are brass? and they're mated into aluminum which has a very different coefficient of thermal expansion...as the engine goes through its normal daily heat cycles, the aluminum eventually breaks the fittings free no matter what method I tried to attach them together.

The purpose of the coolant flowing through the throttle body is to allow the engine rpm to drop once the engine reaches operating temperature. There's an air valve with a heat-activated spring behind it which opens up when it gets warm. With it bypassed, I had to turn the idle way down on my engine.
mine wasn't leaking that bad either. i let my girlfriend at the time drive the truck around town and it, of course, blows completely while she's driving. and, of course, she doesn't have enough sense to pull over immediately.
that was the cause of my first head job. i learned the hard way, that small leaks can turn into large ones in an instant. i also learned to not let other people drive my rover.

discojax, i've had mine bypassed for 4 years and haven't had a problem in NC, so i'm sure you'll be fine in FL. i'd leave it be.
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Old 02-17-2012, 03:30 PM   #11 (permalink)
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As I said earlier. Mine was leaking a little. Replaced the plate and gasket. Took all of 20 minutes. Not leaking now. And I know it's not going to ice up on me. No matter how remote the possibility I don't have to find out the hard way if a cool moist SC day will cause it to ice. Piece of mind. Just sayin.


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Old 02-17-2012, 03:31 PM   #12 (permalink)
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I guess peace of mind is the proper saying. Piece of mind is a Iron Maiden album.


02 D2 118k. OME springs and shocks. Tom woods drive shafts.
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