Here are the pictures of the stock cap and the updated cap. The stock intercooler system cap is on the top and does not have the fill valve like the new cap.


On the second picture I have the fill valve lifted up. When the system cools after a heat cycle it will draw coolant in from the reservoir. When the system is hot it pressurizes and wont let coolant out until it gets to the pressure rated on the cap. I used a 13PSI cap.

 

Cheers Flight Test If you don't mind can you provide a link to the correct radiator cap that I will need -otherwise knowing me I will end up with the wrong one!

In simple terms can you explain what benefit the new radiator cap does in comparison to the stock one?

Again thanks for the advice you are providing to everyone.

 

I found this write up on radiator caps which I found interesting and albeit not for Mercedes I think this is what Flight Test was saying about the different caps

http://www.mgb-stuff.org.uk/radcap.htm#

 

Here is a picture of the part number for the cap I used. It almost looks exactly like the factory one but has the fill valve.

It was purchased from O'reilly Auto Parts. The price was $6.99.

Here is a link
http://www.oreillyauto.com/site/c/de...eyword=HP-7013

 

I'll be doing all this to mine here in a couple of weeks. I absolutely hate having to always check the intercooler coolant levels every other time i drive the car and using a vacuum bleeder to keep it filled properly.

I don't know if anyone else notices, but the back of the filler neck, with the open port right below the cap, seems to always have some dried up coolant. Either right below it or at the firewall portion of the insulation. So i am sure that this is where the coolant goes, it has no where to go once heated up so it seeps out of the back. I've tried two new OEM caps so i know it has nothing to do with the cap itself. Just a ****ty design IMO.

Thanks for the part number Flight Test.

 

WHTEVO, You are totally correct. That is what started me down this path. I had just bled the system and started up the car. As it got hot I could see the coolant dripping out of the water neck through the nipple just like you described. Once that liquid is pumped out there is no way for it ever to get back in, so no matter what over time your stock system will get air in it.

Good luck on the install, it looks factory when it is all together. No one will ever notice it. No more bleeding. It does it all for you!

 

Thanks Flight Test

 

Unfortunately O'reilly auto parts don't ship outside usa so no chance of me getting it over here to Ireland.


I have been looking on the net to see if I can get one from the UK or Ireland and seen this webpage - does anyone know if any of these will do the same job as the one from O'reillys.

http://www.carbuildersolutions.com/u...nks-caps-necks

 

I found this on ebay. It is manufactured by another company so I guess it is the same but the picture they are showing is different (maybe just a sample one) they ship internationally:

http://www.ebay.com/itm/Radiator-Cap-Standard-CST-7013-/331579592455?hash=item4d33af0f07&vxp=mtr

 

Thanks. If I could get an equivalent one here in Ireland that would be great hopefully Flight Test gets a minute and points me in the right direction on the webpage I posted for a equivalent one.

 

Just go to a local auto parts store with your stock cap. Ask for a 1980s vintage Chevrolet truck cap. Make sure it has the little valve on the bottom.

 

For your info. The 70 represents the cap type and the 13 is the rated pressure. You could also use a 7016 or 7020. Which is a 16 or 20 PSI cap respectivly.

 

I bent the sheetmetal and mounted the jeg's reservior on my s65 this morning as outlined above. Went smoothly. Gonna get a radiator cap today. Was thinking about getting 7 psi cap and running 20% antifreeze 80% distilled water + water wetter. This should give boiling point of 235f or so and good heat transfer. Changing out stock pump for the 010 bosch pump as well. 13 psi cap would give 250f boiling point, but concerned about putting too much pressure in the intercooler circuit. Less pressure the better for sure, but at the expense of boiling point. Not too worried about freezing point as I live down south and the car stays in the garage. 20% antifreeze will give freezing point of 15f or so. I won't drive it on cold days anyway as it will wear summer tires year round. The ideal mixture and pressure cap would be different in different climates. Want to run as little antifreeze as possible to get best heat transfer and thus lowest intake air temps.

 

I think you're spot on about the anti-freeze content. IC systems don't work well with high antifreeze, because the small high speed impeller is prone to frothing the coolant.

The cap pressure isn't important though. This is the low temperature cooling system, and temperatures never get anywhere near boiling.

Nick

 

Why do we need an overflow if the expansion is minimal?

 

If the internal pressure of the intercooler coolant circuit never exceeds the cap pressure then there is no need for an overflow tank. The system will remain sealed. If the pressure ever exceeds the cap pressure then fluid will be pushed out of the system.

From the earlier posts in this thread, it looks like pressure is exceeded at least to some degree as, folks are having to refill the little reservoir tank. Even if the fluid never boils, water still expands as it gets hotter. The only parts of the system that would accommodate this extra volume would be the rubber hoses as they can expand a little bit, and water only expands a little bit as it is heated, so the extra volume could be accommodated here. Also any air voids in the system could compress as the liquid expands.

Having said all of this, I tend to agree with your thought that pressure will never get very high in the system. I thought that the fluid might get heated up some from passive radiation after the engine was shut off and air was no longer moving through any of the system.... If the fluid never boils, then in order to let the system work as good as it could, you would probably want to run a lower pressure cap so it could push the air out easier and then suck back in liquid thus keeping the system totally bled all the time....... May not want to run TOO low pressure cap in case the cap is on the high pressure side of the pump. Would be awful for the pump to push the cap open and lose fluid that way. I'm sure I'm overthinking this, but that is what I do

As to why it is needed, it probably isn't but seems like a good idea and would help keep air from getting into the system as everything heats up and cools down.

 

I installed the overflow as described , using the Willwood Brake resevoir. My system seems to be pushing coolant out of the pinhole air bleed in the cap after hot shut down. I installed a new factory cap, because I thought my original might be bad, but it still pushes out coolant.
Has anyone experienced this ?

 

This entire project started out because I noticed the nipple at the back of the intercooler filler cap was leaking right after the system was vaccuum bled. It would drip drip drip. After a couple weeks I would open the cap and there was a bunch of air under the cap. It was no longer full. The system gets real hot at idle especially with the AC on. All the expansion forces the water out. I think at first you will see some liquid being forced out of the radiator at first until all the bubbles get forced out of the system. For the time being put your reservoir as high as you can, almost touching the hood. This will help vent the bubbles in the line. After a couple dozen heat cycles it should be good.

Please keep us posted on what you see. Have any of the users out there popped the radiator cap of lately and smiled when it was totally full?

 

I will give it a few hear cycles and see if the loss of coolant through the plastic reservoir cap stops. I did some research on the radiator cap issue and changed to one that will allow coolant to flow both ways. I am concerned about the 20psi rating of the factory cap, as that seems quite high.
I will say that the biggest help in cooling the air charge has been methanol injection. I still want the intercoolers to function at 100%, but the methanol makes these engines perform strong no matter what the outside temperature is.

 

So how did this eventually turned out for you guys?

 

I still lose coolant from the plastic Wilwood resevoir on a hot day. The cap is designed with a pinhole for air transfer, and that is where coolant escapes. I guess it's the same situation as coolant coming out the overflow nipple on the stock "resevoir". When liquid expands, it has to go somewhere.
However, IAT's are not an issue at all since installing methanol injection. On a hot day, I run at 30-40 over ambient

 

Ok
Just wanted to know.
Looked like a neat solution.
Im also going for water/meth soon.
But as you said want the intercooling system to be as good as possible anyway

 

Which injection system you use? Is it plug and play?

 

I'm using the Wilwood reservoir too and not loosing coolant. I did for a while after installing the Killer Chiller, but I think it was more just the last of the air burping out of the system and pulling some coolant back in since I have gonn a couple months with no change in fluid level. My coolant never gets very hot with the Killer Chiller though.

 

I am using Snow Performance Stage 2 universal kit. It comes with the basics, but thats all I really wanted. I used the factory washer reservoir so I have a low methanol warning, and I didnt want to plumb all the way to the trunk.

Glad to hear the Wilwood cap venting will stop. That makes sense that the air is working its way out. I dont drive the car much, so I could see it taking awhile.