Radiator Cap ?

[Greenleaf]

Question about the much overlooked radiator cap. Mine is rated at 15 lbs!! Is this normally used Sure seems high. It has the familiar Chrysler/Dodge symbol on it.



What have you guys got?



GL

 

[RAvery]

The 15 lb cap is O/E. 15 lbs. is what most cars and trucks use. Some may be higher or lower depending on vehical specs for temp. The higher rating on the cap the higher the boiling point of your coolant. It won't make it run any cooler, just delays boil over. Circle track and race cars are the most common to run higher caps. As it does put more stress on the radiator, hoses, and heater core. Stay with the 15. By the way I own a radiator shop.

 

[RClark]

I was thinking of replacing mine as the pressure test took it to 14 psi, dropping to 13.

All the parts stores listings called for a 16 psi cap. Any problems?

I'd be happier with a 14psi cap.

 

[paccool]

Hey Scott, I thought the water pressure on the inside was to keep the boost pressure from pushing the head gasket inward! :-laf



Just remember that the higher the pressure the higher the boiling point.



This worries me cause everytime someone brings up things like this it seems there is a string of related problems. I keep seeing comments about leaking head gaskets and keep watching for coolant loss in my truck.

 

[Greenleaf]

I know the member above recommended keeping the 15lb cap, but... ... ... ... ... ... ... ... .



For many reasons I dun changed it out to the 7 psi model, sorry... .



I can't see needing any more pressure than a 5. 9 in a bus which operate the 7 psi cap and run under one holy heck more of a load than my little pickup. Besides, the darn radiator hoses are like rock solid and stay that way, even when the engine is cold. I didn't like having all that pressure in there all the time. The new cap doesn't keep the high pressure in there like the old one did. I tested them both and the old seemed to operate ok. I still think it wasn't working right.



Scott

 

[JLEONARD]

Mine says "Keep tight... Do not open hot". That's the kind I'll replace it with.

Just looked up the spec... 16 psi.

That's what it calls for on my marine Cummins as well... . but it also mentions different pressure caps depending on where the makeup bottle is located in height with respect to the engine.

Jay

 

[paccool]

Hey Greenleaf! I told you last week that it worries me when people start discussing leaking head gaskets, etc. Well, I went up to my Son's place this weekend in Washington. Was about 1700 mile round trip, left Friday, got back today. On the way up, the head gasket started leaking water at the front right corner. :{ I put some stop leak in it and was able to finish the trip. Sure kept an eye on the gauges though! The engine ran fine and the oil stayed the right color, the water just seemed to be leaking to the outside. . I'll have an analysis done to be sure. Tried to get into Piers but they are booked up. For your info, one of the things I did was to get a 7# radiator cap. I was pulling about 5500# up and about 2250 back(trailer was empty coming back). Never had a heating problem at all with the new cap. The old one was 15PSI.



This seems to be the weak area for these engines as far as leaks go. Is there a water jacket port in the corner real close to the edge of the gasket?



Now I gotta figure what to do. Just fix it or replace the head with a new o-ring head. That could lead to some real expensive bombs down the road!



Stan

 

[DValentine]

Stan, I had the same issue, leaking on the right corner. I bought a PDR stage one and am very happy with it. While they had it, I had them o-ring the darn thing. If I am not mistaken they will work over your stock head, if you have the time. I couldn't find a significant problem with my old gasket. You are correct in your thought, there is a water passage on that corner. Good luck and PM me for details if you so desire.



Dave

 

[BushWakr - RIP]

Nascar Mark did some tinkering with operating temps a year or so back... he found that these trucks all seem to run a bit too cool. I think he quoted a normal operating temp of about 165*F ... . that is too low. It should be closer to 175*F - 180*F.

So, a slightly lower relief pressure T-Stat would help address that. If you run in real hot country then you may want to stay with the higher 15/16psi cap.



pb... .