ZephTheChef

I wasn't aware they had changed the main radiator size/packaging up front. Glad you chimed in.

Welwynnick

I wouldn't worry unduly about stacked heat exchangers and airflow. It's the norm for modern cars to have three full height heat exchangers - 16mm AC condenser at the front, 32mm intercooler in the middle, and 32mm radiator at the rear. They're cascaded in temperature - coolest at the front, and hottest at the rear.

With water cooled charge cooling, the HE is actually a benign burden to airflow, as the water passages are so slim. Most cars have air-air coolers, which block 50% of the frontal area due to the horizontal air tubes.

When I fitted my full-height radiator/HE, I was indeed worried about airflow blockage, as nobody had done this before. I tried blowing through the radiator out of curiosity, and found very little restriction - the air went straight through. On the road, I saw no difference in the cooling system behaviour - only improvements in the IC performance. I monitored it with STAR, OBD2 and a separate IC coolant temp sensor.

The bigger pump and HE worked great, and the only issue was heat soaking when stationary after a run. The engine compartment is like a 90 deg C oven, and nothing stops the IC coolant heating up unless you open the hood. Insulating the pipes and IC's slows it down a little, but it can't stop it. Sure, there's a small, measureable improvement, butit's almost intangible in use, and it's not worth the significant grief IMHO.

Far better to make an ally heat shield for the coil packs, and extend that downwards to wrap around the coolant pipes as well, and shield them from direct line-of-sight to the turbos. That's easy. Like this:

Welwynnick

Yes, bleeding is difficult. The V12TT IC system is, by the standards of modern cooling systems, a TERRIBLE cooling system. Cooling was solved a long time ago, but Mercedes forgot about all they learned, and made every mistake all over again.

If its working, it works well, but it's needlessly difficult to maintain. A tiny bit of air in the coolant causes frothing and a huge loss of cooling capacity.

The pump uses a commutator and brushes, which wear out. Problem is, you never know for sure when it fails.

The dynamic seals leak eventually, but it's difficult to check the coolant level as there's no header tank.

The system is full of air locks, and there's no provision for bleeding. So the only way to bleed is with a vacuum refill tool like this:




This is similar to the Mercedes special tool, and uses a compressed air vacuum pump. However, that only generates about 80% vacuum. That isn't enough to get all the air out of the system, so there will still be airlocks, and it has to be done again and again.

The answer is to use a real vacuum pump that gets over 99% vacuum, THEN the system will be filled and bled properly.

Like the suspension and like the ignition, it shouldn't be like this, but Mercedes made a leap with the W220 and the V12TT in particular, but tis what we've got and there are ways to work with it.

Nick

freestylebiker3

one of my old posts, just in case you need it...

https://mbworld.org/forums/cl55-amg-...p-upgrade.html

Welwynnick

The Meziere WP135 is like the Johnson CM90 - it's no better than the Bosch -010 pump when installed in our systems.


Nick

freestylebiker3

the Meziere pump i installed provides 20 GPM, and worked great for my car. if you personally like the Johnson pump more then the Meziere, all power to you, i cant argue with that.

both pumps will work well, i personally have worked with Meziere more then johnson, so i trust it and understand it better..

Welwynnick

I'm sure your car works great with the Meziere, and that's what matters, but it doesn't flow more than the Bosch. IC systems have too high restriction for high flow pumps like Meziere and Johnson. 20 GPM is the open outlet figure.


Nick

ZephTheChef

I'll second that. I don't think even my 55gpm Meziere would outflow the stock pump in this system. It does great in my Buick with 1.25" lines. Which may not sound that much bigger but it's 3x the flow path of a 3/4 line. These systems are just too restrictive for those engine cooling pumps designed with just a few psi pressure in mind.

Welwynnick

I think 3/4" pipes are universal, but too small for powerful engines. You might think it's water, so its got thousands of times more heat capacity than air. But its also got more density and viscosity, so it moves MUCH slower. When you compare the mass flow rates, we have around 400g per sec of both, and that's a bit marginal. We could really do with bigger pipes!

Nick

ZephTheChef

Yeah, I assume you mean volumetrically when you say thousands of times. If you have the same mass flow rate on both sides, you're going to get the water temp rising 1 degree F for every 3-4 degrees F (depending on ambient humidity) of cooling on the air side. That's going to heatsoak the water pretty quickly when your turbo outlet temps are 300 degrees F!

black-series

Thanks again for all the help. As you said, of course bleeding didn't work without special tools, so I ordered a vacuum pump that is supposed to lower the pressure to 0,05 mbar which should be sufficient for a vacuum. Do I still need a special vacuum refill kit like the one in your link? Could you roughly explain how to connect the pump to the car for proper bleeding?

ZephTheChef

I have had "moderate" luck with the venturi-type vacuum tool like that. The actual air conditioning vacuum pumps work much better, but still need to be used with a refill kit like what you purchased. Typically with those kits, one of those adapters will fit the intercooler filler neck and adapt it to fit the main part of the bleeder. Then you hook up shop air and set the valve to let the system build vacuum. Once it's at full vacuum you change the valving so it draws coolant back in through the other hose. It will get most of the air out but you may still have to do some further bleeding. If you adapt it for use with an A/C vacuum pump, you will get all the air out.

black-series

Hi, I didn't buy a Venturi type vacuum pump but a rotary vane pump instead

http://www.ebay.de/itm/Vakuumpumpe-5...3D131861240602

I managed to get hold of the workshop cap that enables me to connect the hose to the intercooler filler neck. So I guess I need a splitter with two valves to enable me to draw coolant back once at full vacuum, right? Is it better to order a whole refill kit additionally or just the parts I need (valves, splitter, hoses)?

ZephTheChef

Oh, sorry, I see that the picture was in the quote of Nick's post, not yours. Yes, if you have an adapter for the factory cap basically you need a valve that will switch the connection from the system from the vacuum pump to another hose, which you will have primed with coolant and drawing from a bucket of coolant with enough capacity to fill the system. This can either be done with multiple straight-through ball valves, or probably with a single 3-way valve.

black-series

Ok, thank you for your help, I will try to get a 3 way valve.

ZephTheChef

Just verify you get it set up the right way before you try it with coolant. Would suck to accidentally switch the coolant supply to the vacuum pump side instead of to the intercooler circuit.

black-series

That's a good advice, that really would suck, even more than bleeding the whole thing

Welwynnick

Yes, you would still need one of the vacuum refill kits, or something similar. You need a way to get the coolant in without letting any air back in, having evacuated it.

This is the one I got. It has a tapered filler adapter, which I don't like, but it has TWO valves - one to isolate the vacuum pump (on the left) and one to isolate the coolant. I think this is ideal, and it's cheap.





The reason why a rotary vacuum pump is more effective than a compressed air / venture pump, is that a deep vacuum in the cooling system will boil the water at ambient temperature. That means the system will be filled with water vapour, and all the air will be purged out. Not just 90% or 99% or 99.9% of the air, but all of the air.

Then, when you fill the cooling system, all the water vapour condenses back to water, and you get a complete fill. You need at least 1 kPa vacuum for that to happen (depending on ambient temp). Venturi pumps don't get close, which is why they're hit and miss.

Nick

black-series

Thanks for the explanation Nick, this will help a lot. I had a similar setup in mind but the whole kit makes it a little easier.

black-series

Hi guys,

finally I managed to get all the parts I need for bleeding my car, but I am unable to create a vacuum. Reason being is that the pump always pulls water out of the system together with the remaining air, so I have to turn off the pump to prevent the water from entering the pump. Is there a special trick to it? Do I need a vacuum tank or something?

Marcel

Welwynnick

Don't run the pump when you evacuate. Vacuum filling is static bleeding.


Nick

ZephTheChef

I have best luck starting with as empty a system as possible.

black-series

Ok, I will try to use a vacuum tank, this might make the process a little easier

black-series

I have one question concerning the intercoolers. I already installed the Renntech heat exchanger + pump upgrade and made sure that the system is bled properly.
I am running a Renntech tune which should provide between 670-680hp and 1150NM (limited) This was a noticeable improvement, especially at higher speeds.
Will an intercooler upgrade be worth the effort and lead towards a similar jump in performance or does it only help the car to stay cooler?
Slightly off topic, sorry: Will reinforcing the gearbox (by Renntech or MKB) and removing the torque limiter (which leads to 1200-1250Nm) help the car to be faster at speeds above 150 km/h or is it not worth the effort and cause more harm than good? If it only creates wheel spin and stress even at high speeds, I won't do it.
I do not want to modify my car any further by trying to get more horsepower, I just try to make use of everything the car already got by addressing the two bottle necks, transmission and cooling. Thats the reason for my two questions.

Welwynnick

Better intercooling will always increase power, but the Renntech pump is pretty good, and I don't think any further gains would be great. Zeph and I both have an BMW X3 engine radiator for an HE, so we went a bit overboard.

What does the Renntech HE look like?

Nick