4lb vs 7lb pressure cap

Cacti_Ken · Post by **Cacti_Ken** » Wed Jan 23, 2008 12:39 pm

Which is correct for the L134 engine, a 4lb or the 7lb pressure cap?

Ken

Post by **wesk** » Wed Jan 23, 2008 9:22 pm

Depends on the chassis it is installed in. The Civvy specs are: CJ2A and CJ3A 4 1/2. DJ3A 7.
Military specs: MB 4 1/4, M38 4 1/2 and I believe the CJV35 is also 4 1/2.

Cacti_Ken · Post by **Cacti_Ken** » Wed Jan 23, 2008 10:30 pm

Good grief I had both wrong...
Ok, well the old cap that was on mine was 4#. I replaced it with another 4# cap I got at NAPA. I was just curious as I have seen one ebay alot that is 7#'s that fit the large mouth radiator.

I haven't had a problem yet with over flow with the 4# cap.

Post by **wesk** » Wed Jan 23, 2008 11:19 pm

The 7 Lb cap goes on all the F134's.

ktm25089 · Post by **ktm25089** » Tue Apr 08, 2008 12:45 pm

if i remember right my cap is 16lbs.it it a problem with my f-head?they was send it to me as the stock military.
thank you

artificer · Post by **artificer** » Fri May 02, 2008 5:02 am

I haven't had a problem yet with over flow with the 4# cap.

The cap pressure has technically has no real bearing on overflow...it does have relevance to the temperature that the coolant will boil and subsequently exceed the pressure the cap can maintain e.g. 4#. Then you loose coolant out the overflow.
I use a 7# cap on my L134 and it often runs at 220-230F (until the electric fan comes on/I don't run a fan on the water pump pulley) with no loss of coolant

ktm25089 · Post by **ktm25089** » Fri May 02, 2008 11:35 am

i think that 220-230 is too high for this type of engines.

artificer · Post by **artificer** » Fri May 02, 2008 12:01 pm

i think that 220-230 is too high for this type of engines.

With all due respect I would like to know on what reliable basis you make this statement or is this just personal opinion?

I am quite happy, the engine performs wonderfully, there is no coolant loss and no obvious negative effects...possibly some positives.
That being said does not indicate I am recommending others do as I do.

The original question regarding radiator caps....with a 7# cap you "can" run at up to 230 with no coolant loss from my in field experience.

ktm25089 · Post by **ktm25089** » Sat May 03, 2008 1:04 am

sorry,i didn't want to offend you.
this is only my personal opinion because i see on all the manuals say 180f operating temp.
and i'm scared when my engine climbs under heavy load and very warm days in collision at 190-200.
i have a 16lbs cap.it's military style but i will change it with the proper 7lbs cap.
sorry again

George

artificer · Post by **artificer** » Sat May 03, 2008 1:27 am

I'm not offended at all.
Just wanted to know if there was foundation to what was being said.
Because thermostats have opening and closing temps does not mean that is the temperature things will run at and that's where the 180 degree number presumably comes from.
As for a 16# cap I believe you are doing the right thing getting back to 7#
This (16) is much too high, not needed and could damage the radiator, cause the water pump seal to leak or pop hoses off, as the system was never meant to be pressurized so high.
One thing to remember is that latter day temp gauges have no numbers on... just zones including "normal or green" so folk don't see "numbers" they think are higher than things should be and panic.