Cooling System - Overflow Cap

[Ta2dResqr]

Looking at another members mod list I noticed a radiator cap. I remember when running a boosted import, I upgraded from a 1.1 bar to 1.3 bar to get an extra little cushion (~8.7*) and it allowed the coolant ratio to be played with a little more without fear of boiling. I started looking around and all I can find is 1.1 bar for our application. Has anyone played with this at all? Is it avoided due to the cap being on the overflow instead of on the radiator? I was able to find some newer applications that used the 1.3 bar cap but I am not sure if it is the same fitment. I also found Super Duty trucks used a 21 psi (~1.44 bar) cap.

 

[kryptto]

1.1 bar is 16 PSI in case this helps. 1.3 bar is nearly 18.9 PSI

I did do some poking around to all kind of sites - 16psi or 1.1bar seems to be the fare. Aren't you concerned you will cause the reservoir to spring a leak?

 

[SM105K]

1.1 bar is 16 PSI in case this helps. 1.3 bar is nearly 18.9 PSI

I did do some poking around to all kind of sites - 16psi or 1.1bar seems to be the fare. Aren't you concerned you will cause the reservoir to spring a leak?

I would say, he is just looking for that cushion.

 

[Ta2dResqr]

1.1 bar is 16 PSI in case this helps. 1.3 bar is nearly 18.9 PSI

I did do some poking around to all kind of sites - 16psi or 1.1bar seems to be the fare. Aren't you concerned you will cause the reservoir to spring a leak?

I am not concerned about the system getting a leak. It is less than 20% pressure differential. I have run it on other systems and I have also tested my system at 20 PSI. When using a pressure tester, I usually set it for 4 or 5 PSI higher than the cap looking for weak spots. Rather find it in the garage than on the road. In theory, the system would still operate as normal unless it was being stressed. If your 16 PSI cap reaches 17 PSI, it will "burp" and allow coolant out the overflow hose. Doing this enough would cause a low coolant issue. The fact that it doesn't happen is because the system generally operates under that level. This would mainly be a little extra safety for "spirited"/track use, the additional heat generated by more power/boost, and anytime you may get stuck in traffic on a really hot day. It would essentially allow the car to get about 9* hotter before the coolant boils.

 

[kryptto]

Doing this enough would cause a low coolant issue. The fact that it doesn't happen is because the system generally operates under that level. This would mainly be a little extra safety for "spirited"/track use, the additional heat generated by more power/boost, and anytime you may get stuck in traffic on a really hot day. It would essentially allow the car to get about 9* hotter before the coolant boils.

Thanks for explaining your thought process - I understand the intention much better. Shame I was having the same issue as you. Very hard to find.

 

[Mahu24]

I am not concerned about the system getting a leak. It is less than 20% pressure differential. I have run it on other systems and I have also tested my system at 20 PSI. When using a pressure tester, I usually set it for 4 or 5 PSI higher than the cap looking for weak spots. Rather find it in the garage than on the road. In theory, the system would still operate as normal unless it was being stressed. If your 16 PSI cap reaches 17 PSI, it will "burp" and allow coolant out the overflow hose. Doing this enough would cause a low coolant issue. The fact that it doesn't happen is because the system generally operates under that level. This would mainly be a little extra safety for "spirited"/track use, the additional heat generated by more power/boost, and anytime you may get stuck in traffic on a really hot day. It would essentially allow the car to get about 9* hotter before the coolant boils.

Have you had any issues with your car getting too warm? I beat the c*** out of my car almost daily and never seen the coolant temps very hot on my tuner

 

[Ta2dResqr]

Have you had any issues with your car getting too warm? I beat the c*** out of my car almost daily and never seen the coolant temps very hot on my tuner

Not yet, however, I have now gone to Stage 3 turbos. I am expecting more heat to be generated. Combine that with the fact that I regularly experience ~15 minutes of spirited driving followed by ~30-45 minutes of idling, and I would like to have the extra cushion.

 

[Mahu24]

Not yet, however, I have now gone to Stage 3 turbos. I am expecting more heat to be generated. Combine that with the fact that I regularly experience ~15 minutes of spirited driving followed by ~30-45 minutes of idling, and I would like to have the extra cushion.

Stage 3 CR Performance turbos?
I ran 9, 1/4 mile runs, back to back and didn't see my coolant temp raise at all.

 

[Ta2dResqr]

Stage 3 CR Performance turbos?
I ran 9, 1/4 mile runs, back to back and didn't see my coolant temp raise at all.

TurboBay Stage 3.

 

[Ta2dResqr]

Well I talked to MotoRad (who owns Stant) and got it figured out. The correct cap with a 20 psi rating would be a T54.

MotoRad Taurus - T38 16 PSI
MotoRad - T54 20 PSI

FORD	FOCUS	2008-2011
LAND ROVER	DEFENDER 110	2020-2021
LAND ROVER	DISCOVERY	2017-2020
LAND ROVER	RANGE ROVER	2016-2021
LAND ROVER	RANGE ROVER SPORT	2016-2021
LAND ROVER	RANGE ROVER VELAR	2018-2021
MERCEDES-BENZ	ML320	1998-2003
MERCEDES-BENZ	ML350	2003-2005
MERCEDES-BENZ	ML430	1999-2001
MERCEDES-BENZ	ML500	2002-2006
MERCEDES-BENZ	ML55 AMG	2000-2003

Using the 2008-2011 Focus:
Motorcraft - 9S4Z-8100-B or RS259

I went with a Motorcraft part for the OE look and quality. You can cross reference the MotoRad or Motorcraft part numbers to the manufacturer of your choice. I know Dorman and Stant both have applications that match. Make sure to look for the overflow or degasus cap. The Focus also has a traditional style radiator cap that you do not want for this application.

 

[kryptto]

Well I talked to MotoRad (who owns Stant) and got it figured out. The correct cap with a 20 psi rating would be a T54.

MotoRad Taurus - T38 16 PSI
MotoRad - T54 20 PSI

FORD	FOCUS	2008-2011
LAND ROVER	DEFENDER 110	2020-2021
LAND ROVER	DISCOVERY	2017-2020
LAND ROVER	RANGE ROVER	2016-2021
LAND ROVER	RANGE ROVER SPORT	2016-2021
LAND ROVER	RANGE ROVER VELAR	2018-2021
MERCEDES-BENZ	ML320	1998-2003
MERCEDES-BENZ	ML350	2003-2005
MERCEDES-BENZ	ML430	1999-2001
MERCEDES-BENZ	ML500	2002-2006
MERCEDES-BENZ	ML55 AMG	2000-2003

Using the 2008-2011 Focus:
Motorcraft - 9S4Z-8100-B or RS259

I went with a Motorcraft part for the OE look and quality. You can cross reference the MotoRad or Motorcraft part numbers to the manufacturer of your choice. I know Dorman and Stant both have applications that match. Make sure to look for the overflow or degasus cap. The Focus also has a traditional style radiator cap that you do not want for this application.

Congrats, I went to MotoRad site and Stant nice job getting them to x ref.