radiator cap

[Exekiel69]

The one I have on my truck I have it for a few months it saids 13 lbs on it. I have noticed a few drops of coolant around it and a drip of coolant around the inner edge of the rad, this only happened after driving on highway for some miles (last 3 days) so the coolant is coming out of from the cap. There is no leaks in anywhere else but from the cap (rad is new) so I wonder if these one set for 13lbs is not enough. Any thought's on this?

Thank you.

 

[OkieGringo]

My radiator man told me to use a 7 lb cap. Higher pressure is ******* the whole system and can make marginal seams/seals blow. OEM for the eariler 7.3s says 7 lbs. If a good 13 lb'er is not enough to hold the pressure, you have a problem in the system somewhere. Get a new cap 7 lb and be sure the overflow tube connection at the cap is tight. OkieGringo

 

[Exekiel69]

OG yes I do have a problem on the cooling system. I have replaced rad, tstat (motorcraft), fan clutch and still the engine gets allways to 200f and 210f or more on the summer but after all those modifications I give up on it bc there was nothing else to change with out major modifications. btw Mel timed my ip so that is out of the question. Anyway I thought 13lbs was the right one after I saw it on another member's truck, now I'll go and get a 7lbs and see what happen. Last few days I noticed it got up to 210 on the highway, only thing I changed was the fuel additive from stanadyne to power service bc it was easier to get.

 

[Mojave Red]

My $.02: There's nothing wrong with temps around 200-210. I frequently see 200 when I climbing a grade empty - even when it's cool out. From what I've seen on this (and the other) board, temps around 220-230 are not uncommon when hauling a load in the heat of the summer. A few years back I overheated while on vacation. I replaced my fan clutch, t-stat and radiator cap (to an OEM suggested 13lbs one). I'm convinced that the radiator cap had more to do fixing the problem than anything else. My problem was compounded by the fact that my reservoir was cracked and had lost all the overflow. Water boils at higher temperatures when under higher pressure. So, I think the trick is to keep your coolant from boiling right out of the cap. Ultimately, I think the only way to keep your temps down below 200 no matter what the conditions are, is to install a high dollar "mongo" radiator. I think Travis finally found success going down this route. And yes, advanced timing will cause you to run hot too.

brian

 

[shorthair]

if coolant is blowing past a 13# cap you might have a bad head gasket thats letting combustion pressure into the coolant, hope not.

 

[Dsl_Dog_Treat]

I see 215 degrees in the summer time on Goldie all the time. Of course the sending unit is installed on the drivers side head. deffinitly would be running the 7 lb cap tho.

 

[Exekiel69]

Well just put ON a 7lbs cap, will see wath comes tomorrow. Some posted the recommended cap is 7lbs others posted 13lbs, wich is the recommended one then?

- Mojave Red. The ip was dynamically timed by Mel at the 2005 rally.

The gauge sender is located on my driver side head at the front, I see 200f temp allways or higher in summer with ac and all. Some times I've seen 230 with ac going up hill no load but that was last summer without all the updates will see this coming summer.

The rad is new, Travis suggest to get the bigger rad, should have listened .

thank you.

 

[F350camper]

I've never had good luck with stant caps. I'd get a motorcraft one.

 

[Exekiel69]

I've never had good luck with stant caps. I'd get a motorcraft one.

school Me on this one, what diference does the cap will make since I changed from 13lbs to 7lbs?

 

[Mr_Roboto]

OK, back in the old days when every car didn't come with A/C, it was generally recommended that a non-A/C vehicle used a lower pressure, and a A/C car would use a higher pressure cap. This had to do with the higher heat load from the A/C system.

Basically what I am saying is that both recommendations are probably right. A higher pressure increases boiling point and a higher operating pressure (within reason) increases combustion efficiency, especially with diesels.

 

[Exekiel69]

Well I have ac on my truck (only use it when the lady rides on it ), then, I should not have bought this new 7lbs cap?

I don't think the temps problem on mine are bc of the cap but I will drive it tomorrow and see if it made a diference. Then again, if the cap makes the coolant boil at higher temps could that be wy I have colant spills on top of the rad around the cap on the first place? Could the coolant be the problem?

 

[OkieGringo]

I had a seam leak, caused by poor solder joint when I had the 5-row core put in in Baja. I took it out and to a rad shop(15 miles away) to have it fixed. The guy suggusted that I use a 7lb cap(he gave me one free) rather than the OEM 12lb. He said that using a higher pressure cap just puts too much strain on all the system and if the engine gets soo hot as to need that much it's already too late and way past safe for engine. Pressure cap increases boiling point 1.5 deg/1lb of pressure. Water boils at 212+(12x1.5)=230. A 50/50 mix Antifreeze raises boiling point to 265 deg(way higher than I EVER want to see my coolant temp), add the (12psi times 1.5psi cap=18deg) and you're up to 283 deg

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. My engine is a 91 with a 12lb cap and had A/C until I ripped it out(Another story for another time). I'm now running with a 7lb cap. OkieGringo

This below, was posted over at TDS by "Runboy"

Well, the previous owner had installed a 16lb rad cap! I went looking through the parts books and my truck (89) called for a 7lb. 90 they went to 12lb and super duty called for 16lb if memory serves correct.
Anyways, cap has been replaced with 7lb and I am curious to see if some of the top tank seapage issues are resolved.
Mike

 

[towcat]

ez-
i run the 7lb cap on my trucks. there's been naysayers over the years over the 7lb cap, but I have plenty of trucks/labrats out on the road with the same cap with no negative results on the cooling system whatsoever. In fact the radiators lasted longer outside of foreign object strikes. I do have an IC and AC in front of mime and it does run warm on 110 deg days. otherwise, I have never had a worry whatsoever.

 

[F350camper]

I don’t have an opinion one way or the other on 7 lbs vs 13 lbs caps. But I do think it’s worth getting a Motorcraft cap.

So just for reference…
7 lb cap Motorcraft RS-68
13 lb cap Motorcraft RS-62

I’ve had more than a few Stant caps cause leaks because it should be opening at 13, but doesn’t. I’m not sure if this is due to the spring, or diameter size of the plunger, but I don’t like them, or buy them anymore…

 

[Exekiel69]

I don’t have an opinion one way or the other on 7 lbs vs 13 lbs caps. But I do think it’s worth getting a Motorcraft cap.

So just for reference…
7 lb cap Motorcraft RS-68
13 lb cap Motorcraft RS-62

I’ve had more than a few Stant caps cause leaks because it should be opening at 13, but doesn’t. I’m not sure if this is due to the spring, or diameter size of the plunger, but I don’t like them, or buy them anymore…

Well the new 7lbs cap is already ON so will see if anything changes, but thank you for the part # I will try to get one since it is better to have the motorcraft parts most of the times. I will drive it for a few miles today will see if anything changed.