Radiator cap psi

Case1000c

New User
Need to know what radiator cap pressure I need, I bought
a replacement cap and it says 7psi, Im having coolant
blow out overflow. Any other ideas other than the cap
isnt high enough psi? Thanks in advance.
 

Is the cap the right length for the depth of the radiator neck? How full is the radiator when cold, couple inches below the bottom of the neck?
 
I can see the fins inside the radiator, maybe I just had the radiator to full? Should I try to operate it the way it is and keep an eye on the temperature gauge?
 
(quoted from post at 15:54:14 08/16/22) I can see the fins inside the radiator, maybe I just had the radiator to full? Should I try to operate it the way it is and keep an eye on the temperature gauge?

Perhaps it was too full, they need room to expand as they warm up.

A cap can lock in place but be the wrong length down into the radiator neck to seal properly. measure the depth of your radiator neck and see what the cap you bought is spec'd for.
 
(quoted from post at 16:46:17 08/16/22) What temp thermostat do you have? That 7lb cap will support a 180 but not a 195.

I'm curious, what is your backup for saying a 7-pound cap will not support a 195 thermostat? I know a JD 2030 uses a 7-pound cap and the thermostats offered by John Deere for the same 2030 are 160, 180, 192, and 205. I run a 192 in mine with no problems. A 50/50 coolant mix raises the boiling point from about 212F (plain water at sea level) to about 220F. Each pound of pressure increase raises the boiling point another 2 to 3 degrees F. So, a cooling system (50/50 mix) with a 7-pound cap will have a boiling point of about 234F to 241F when under pressure.
 
I tried to find a replacement cap, so I used a part number I found online. Do you mean the temperature that a 7psi wont support? Thanks.
 

One can guess you are asking about a Case 1000C, but you should really include that info in your post. We don't remember everyone and their machine that posts and going by a handle to determine what one has for a machine is not a sure thing, either. John Saeli's (external_link) website shows a replacement for the A21389 which is the current number for your radiator cap, if this is a 1000c. If you contact him, he may be able to tell you if the cap you have is correct for your radiator.
 

One can guess you are asking about a Case 1000C, but you should really include that info in your post. We don't remember everyone and their machine that posts and going by a handle to determine what one has for a machine is not a sure thing, either. John Saeli's (external_link) website shows a replacement for the A21389 (part number from the Case online 1000C parts book) which is the current number (old number was A10259) for your radiator cap, if this is a 1000C you are asking about. If you contact him, he may be able to tell you if the cap you have is correct for your radiator.
 

One can guess you are asking about a Case 1000C, but you should really include that info in your post. We don't remember everyone and their machine that posts and going by a handle to determine what one has for a machine is not a sure thing, either. John Saeli's website shows a replacement for the A21389 (part number from the Case online 1000C parts book) which is the current number (old number was A10259) for your radiator cap, if this is a 1000C you are asking about. If you contact him, he may be able to tell you if the cap you have is correct for your radiator.
 
Personal experience. While running all is fine the problem comes when you shut off the engine. The temp rises when the coolant stops circulating. I
have used a 7 lb cap with a 195 temp thermostat more than once and after about 2 to 3 minutes after shutoff the coolant will push out of the overflow.
Right now I have a 7 lb cap on my pickup and got tired of the coolant pushing out so I put a 180 thermostat in and no more problems. The older
vehicles that used the lower pressure caps also used colder thermostats. 50/50 mix of antifreeze might not boil after shutoff. I try to keep mine at least 5
above 0 freeze protection in Tennessee. I went to the 7 lb cap on the pickup because the plastic radiator tank had been repaired with JB weld and I
didn't want to risk 17 lbs pressure in it.
 
I believe a 50/50 mix is the general industry recommended coolant mix, other than some extreme cold weather areas (70/30 being about the maximum before boiling point drops and freeze point rises). As far as I know, premix coolants sold are all 50/50 mixes. 5 above zero freeze protection would earn you a cracked block around here, and many other places. I have only seen coolant push out of a stopped engine after an initial fill that had not fully equalized. In my experience, it is not uncommon for people in cold weather climates to run 190+ thermostats, even in older low pressure (4-7 lbs.) systems. (And I do remember using methyl alcohol/methanol antifreezes in old equipment. Those often only used 160 thermostats, 180 could be pushing one's luck in unpressurized or early low pressurized systems, due to the lower boiling point and evaporation of the alcohol. To be clear that mixture is not included in this discussion, as it is no longer commonly used.)

I don't see where running a 7 lb. cap and a lower temperature thermostat, because of risk to a JB Weld patched radiator tank, is proper technical grounds to say the higher temperature thermostat and pressure cap, are a problem. Or that they should be replaced by lower rated components. My current road vehicles all use 13 to 17-pound caps and the OEM surge tanks, as designed. My 2020 and 2030s (7 lb. caps and 192-195 thermostats) don't push coolant out when running or after shutdown (even when worked hard in 95F+ temperatures).

We can respectively agree to disagree. Your system works for you, which is good for you. I don't see it working for me, given my personal experience.

This post was edited by Jim.ME on 08/23/2022 at 05:05 am.
 

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