Xu9j4 Heater Bypass Tube

[petert 554]

I've never seen any discussion about this, so I thought I might direct you to a thread on the Aussie Frogs site, about a car I'm currently building. Given the number of standard thermostats I've seen fitted to Mi16's, I doubt many people understand how it all works, and more importantly, how to remove them.

 

http://www.aussiefrogs.com/forum/showthread.php?t=54945

[DrSarty 90 1 Cars]

I found the whole thread of interest Pete; looks like a good forum.

 

Here's the essence of this bypass tube topic:

 

The Mi16 has a heater bypass tube which is unnecessary in a 205 or a race car. The bypass tube allows coolant to bypass the heater matrix when the thermostat is closed, making the engine heat up faster. When the Mi16 two stage thermostat opens, the rear section of the thermostat (circled in red) closes off the bypass tube, forcing all coolant through either the radiator or the heater matrix.

 

A common mistake is to fit a normal thermostat to an Mi16. This means the bypass tube never closes, allowing hot water to circulate around the block, never passing through the radiator.

 

The bypass tube can be easily removed from the housing by using an oxy torch to heat the aluminium housing. The hole can be plugged by tapping 1/2" BSP and screwing in a plug. The heater outlet is left as is in this case as Phil still wants a heater. Otherwise, this pipe can be removed as well and either tapped for a 1/2" BSP plug or TIG welded over with a cap.

 

A regular 82 deg. thermostat will be used in this application. The standard 205 8V distribution block will be used.

 

It's the last item (in italics) I'd like clarified please: in particular for my build which will be using the S16 block including the metal S16 thermostat housing and cover. Does this mean using an 8v thermostat or just a standard thermostat that's rated at 82 deg?

 

Bypass tube: I was going to lose it anyway if it did, but does the S16 thermostat housing use a bypass tube?

 

And why use the 8v distribution block - less outlets? I've been recommended to use my S16 metal dis block. Any advantages or blanking required here?

 

Sorry for the barrage of questions/

Edited January 8, 2008 by DrSarty

[Super Josh 4]

Seems to be fairly standard practice to remove the tube here in the UK. A couple less hoses to leak and my engine gets up to temperature in around 5 mins anyway.

 

 

 

Josh

[Miles 331 1 Cars]

What I;ve said all along

 

But the S16 uses the same idea abit with a different stat so the rear pipe can be blocked up, (I get all mine TIG welded), The Iron block's also use a different size dist block but the idea of fitting the std 8v is there's no hole to block up and thus reducing MTBF (Mean time before failure).

Also make's the engine install neater, You can access the exhaust nut's easier,

But you can run the older stat housing on the S16 head as the stat housing comes out at a better angle, you just need to make a bung for the oil drain hole on the side of the head.

[petert 554]

The S16 is similar to the XU9J4. Just remove/plug/TIG what you don't need, as in the pic. This is an S16 housing on a 1.9L head. The outlet hose points directly at the side of the radiator, so hose selection is easy. You don't have a choice with the S16 distribution block, as size and bolt spacing is different to the XU9 series. Again, cut off the extra pipe for the bypass and TIG up the hole. The metal looks like rubbish but it welds quite nicely.

 

Just use a std. thermostat in the S16 housing.

 

Also TIG up the extra outlet in the thermostat housing outlet, as in the 2nd pic.

Edited January 8, 2008 by petert

[taylorspug 7]

Ive also always removed the bypass tube, aswell as using the 8v top hose outlet and removing the throttle body heater pipes, makes for alot neater conversion.

[DrSarty 90 1 Cars]

Just use a std. thermostat in the S16 housing.

 

Std. what Pete? S16 or 8 valve stat?

[petert 554]

Std. what Pete? S16 or 8 valve stat?

 

8 valve type, but 82 deg.

[DrSarty 90 1 Cars]

Thanks all. Very interesting. Not new I agree, but nice and clear. The engine bay should as a result be tidier, with more room for cooling and airflow around the engine too.

 

Lubbly jubbly

[GLPoomobile 958]

Although I was aware of this practise, I've never given it much thought before.

 

But would this explain why my Mi's coolant temp climbs very quickly from cold if left to idle? I was a bit concerned when I first experienced it as it went up much quicker than I'm used to with a normal 205 GTI, but the car doesn;t appear to overheat, so maybe it is just due to the bypass pipe.

[James_R 3]

Lighter too

[YADI_SUN 0]

Hi Peter

 

Do you think same thing can be

taking place on T16 engine as well ??

 

thanks

 

Yadi

[James_m 0]

So in summary, what thermostat is actually needed with this setup?

A standard 8V or Mi16?

 

[DrSarty 90 1 Cars]

So in summary, what thermostat is actually needed with this setup?

A standard 8V or Mi16?

 

 

I did ask this earlier. You need an 8v stat, which should be 82degC opening.

 

The Mi16 stat is 2 phase & you don't need that once the metal pipe out the rear of the housing is redundant.

[James_m 0]

Cheers Sarty. Yeah all the info was already in the thread anyway. Must actually read things properly in future!