[67blackcherry]

Originally Posted by Geoff

J Jamnik,
I'm on your side. I cannot see how a hose that sits too high will cause overheating because of so called trapped air. Cars that did not use rad o'flow bottles were filled to about 1/2" to 1" below the cap to allow for expansion at operating temperature. These cars ran just fine with the air space. Top hose higher than the top tank? Why wouldn't the air space in the top hose be considered as one air space with the air in the top tank, as they share a connected passage way.

I don't know either. What I do know is this fix worked on my LeMans; my Firebird had the same problem with the hose and once it's put back together I'll cut down the hose to see if it solves the problem.

Did you read the thread I linked at the top, in my first post? That guy Screamingchief goes into great detail why it's a problem.

Worked for me.

[sts]

Sorry folks, but this one is a total lack of common sense, about as dumb as it gets. I point this out because if a person isn't bright enough to fathom such a kindergarden concept, working under the hood will lead to total disaster. With that, you would be much better off farming out ALL REPAIRS. Sometimes 'mean' is the best help you can offer.

[67blackcherry]

Originally Posted by sts

Sorry folks, but this one is a total lack of common sense, about as dumb as it gets. I point this out because if a person isn't bright enough to fathom such a kindergarden concept, working under the hood will lead to total disaster. With that, you would be much better off farming out ALL REPAIRS. Sometimes 'mean' is the best help you can offer.

Sorry we're not all up to your level of mechanical brilliance.
Funny, I don't recall you offering that solution in my thread "why is my 455 running hot?"

[sts]

Actually, my comment is more dumb than anyone elses because as a former professional mechanic, I shoud know better and should be held to a higher standard.

The hose might create additional burden on the water pump, but it shouldn't create an overheating problem, and the location of the rad cap has nothing to do with the cooling ability of the system.

The top hose is the return hose. And the hose sitting higher--within reason--than the cap has almost zero affect, not enough to cause overheating: Operating the rad at a level a few inches below the cap has the exact same result as the high hose, and a few inches down won't cause it to overheat. I can run my car in brutal heat with half a rad full and it won't overheat. Based on that, how does the position of the rad cap have any bearing on heat transfer?


If it quit overheating when you did that, there is another reason for the reslut. A few degrees in ambient temperature/humidity can make a huge difference.

[fbody_mike]

Originally Posted by sts

Sorry folks, but this one is a total lack of common sense, about as dumb as it gets. I point this out because if a person isn't bright enough to fathom such a kindergarden concept, working under the hood will lead to total disaster. With that, you would be much better off farming out ALL REPAIRS. Sometimes 'mean' is the best help you can offer.

Wow!

What I do know is that my late model car has air bleeds on the high points of the engine because the radiator is lower than the motor, which can cause air to be trapped within the coolant chambers of the engine. If air is introduced into the coolant chambers (was low on coolant, changing etc. ) and if you do not open the bleeders, the engine will overheat.

[screamingchief]

Originally Posted by sts

Actually, my comment is more dumb than anyone elses because as a former professional mechanic, I shoud know better and should be held to a higher standard.

The hose might create additional burden on the water pump, but it shouldn't create an overheating problem,and the location of the rad cap has nothing to do with the cooling ability of the system.

The top hose is the return hose. And the hose sitting higher--within reason--than the cap has almost zero affect, not enough to cause overheating: Operating the rad at a level a few inches below the cap has the exact same result as the high hose, and a few inches down won't cause it to overheat. I can run my car in brutal heat with half a rad full and it won't overheat. Based on that, how does the position of the rad cap have any bearing on heat transfer?


If it quit overheating when you did that, there is another reason for the reslut. A few degrees in ambient temperature/humidity can make a huge difference.

There are almost too many things in the post to even bother addressing...

Sorry,former pro or not you fail cooling systems 101.

Originally Posted by sts

and the location of the rad cap has nothing to do with the cooling ability of the system.

Completely wrong,it has everything to do with the cooling abillity of the system.

Where the cap is located affects the cooling system pressure it sees,that inturn affects the given caps pressure rating for the intended system operation,the pressure present in that given system directly affects the boiling point of the coolant in that system,how more basic can this get than that!

Originally Posted by sts

The hose might create additional burden on the water pump,

Burden on the pump?

How so???

I wont argue an obstruction in the system might raise the pressure in the system by slowing the flow thru the obstructed portion of the system,but that really does'nt "burden" the water pump itself in any specific way,the pump could really care less what the system pressure is,it'll do it's thing regardless,if the pressure in the systen is past a certain threshold,it will just try moving more coolant thru the bypass instead.

Originally Posted by sts

The top hose is the return hose. And the hose sitting higher--within reason--than the cap has almost zero affect, not enough to cause overheating:

That was fully explained in the linked thread,and again that is just not the case.

Originally Posted by sts

Operating the rad at a level a few inches below the cap has the exact same result as the high hose,

Not necessarily.

If the air in the system is exposed to the underside of the radiator cap,any expansion can still be dealt with by the cap,it will purge any required amount of trapped air when the system pressure excedes the caps rating,this will then permit the coolant to flow regardless of the excessive air present in the system.

This is not the situation I pointed out to the thread starters car,his had the radiator hose having just a portion of the hose higher,and the cap isolated from the air,in that case the air will compress slightly and then act as a solid,and obstruct the coolant flow thru the hose,that's not too overly complicated now is it???

Originally Posted by sts

I can run my car in brutal heat with half a rad full and it won't overheat.

Well,if the level is that low,often the coolant temp probe/sensor will become uncovered as well,and thus you wont get an accurate reading anyways,is it not overheating because it's not pushing out coolant,no not at all,that's becuase it's too busy trying to push the air out first,honestly in this situaton,you'll likely have no idea what's actually going with the engine coolant temps,certainly not in any reliable manner.

It's a SYSTEM folks,no one thing takes precedent,they all work together,like pieces in a puzzle.

Ignore one part of the system consistently,and you'll almost certainly have issues at one time or another.

Two basic rules to remeber with cooling systems,water always seeks it's own level,and air will always seek the highest point.

HTH.

[screamingchief]

Originally Posted by fbody_mike

Wow!

What I do know is that my late model car has air bleeds on the high points of the engine because the radiator is lower than the motor, which can cause air to be trapped within the coolant chambers of the engine. If air is introduced into the coolant chambers (was low on coolant, changing etc. ) and if you do not open the bleeders, the engine will overheat.

Late model cars with the rads mounted lower than the engine will almost certainly be equipped with a surge/expansion tank as well,this was discussed in that previous thread.

The bleeds are there usually just to deal with other "problem areas".

But the system itself will employ a design to address the radiator location,and that is what the surge tank does,and that inturn will employ a second pressure cap to deal with purging any air from said system.

This sorta set-up is very common on newer cars,corvettes for instance,it was/is very common on german cars too,the VW scirroco was an early example.

Understand the basics,and all the rest of this starts making a whole lot more sense.

[screamingchief]

As for those mentioning cars with "high" upper hoses and no problems.

That just means those systems coolant flow is just not being inhibited enough to affect the coolant temps to a significant margin.

And I bet everyone wishes that were the case for them.

It's often not,especially with high performance applications.

Often those applications need all the flow they can get to control the coolant temps effectively.

[1970gpsj4speed]

After 40 years orf working on cars for a hobby and Racing Turbo Buicks .Your timing on the first thread for me was perfect .It fixed me up and I learned something new.
I called my son who is ASC certified MEC and he confirmed what you are saying

[GT182]

Will a 4# pressure cap be better than a 15# cap that was original to the GTOs cooling system? I'm running a 4# right now and wondering if it's adequate.

Back to hose position. Before I trimmed my upper hose I was running at 190* with a 160 thermostat. Now the the hose is lower than the radiator cap, the temp is down to 160. I think tomorrow I'll go to a 180 thermostat as that's what I believe should be used. At least they were back in the 60s and 70s. I can't understand why the parts books today say to use a 190 or 195 thermostat.

[67blackcherry]

Originally Posted by GT182

Will a 4# pressure cap be better than a 15# cap that was original to the GTOs cooling system? I'm running a 4# right now and wondering if it's adequate.
Back to hose position. Before I trimmed my upper hose I was running at 190* with a 160 thermostat. Now the the hose is lower than the radiator cap, the temp is down to 160. I think tomorrow I'll go to a 180 thermostat as that's what I believe should be used. At least they were back in the 60s and 70s. I can't understand why the parts books today say to use a 190 or 195 thermostat.

Don (?) from Alumitech radiators explained the cooling system to me in detail - he told me I should be running at least a 15lb cap. I'm running a 16lb cap and since trimming down the hose my car runs all day long at 190* w/a Robertshaw Highflow 180* stat, and we've had a bit of a heat wave these past few weeks. Sorry, don't mean to rub it in...there are advantages to living in So Cal! This on a brand new engine (1000miles on it) and I'm sure once I get a few thousand miles on her she might run a bit cooler still.

[455Grandville]

Originally Posted by sts

Sorry folks, but this one is a total lack of common sense, about as dumb as it gets. I point this out because if a person isn't bright enough to fathom such a kindergarden concept, working under the hood will lead to total disaster. With that, you would be much better off farming out ALL REPAIRS. Sometimes 'mean' is the best help you can offer.

Genius: how is anyone supposed to learn about working on car by farming out he work ?
The man asked a legit question, does that offend you ?

[screamingchief]

Originally Posted by 1970gpsj4speed

I called my son who is ASC certified MEC and he confirmed what you are saying

Not that anyone is gonna care much about this,but I too was an ASE master tech,and that was for over 15 years,honestly it was actually much closer to twenty years before I called that career choice quits,that decision was due to a serious injury & subsequent surgery,that forced my hand on the career change,mostly based on the desire to not take any chances on the potential to aggravate that injury.

I also happen to have a vocational degree for automotive tech/service,got that at the begining to get my foot in the door,and helped with some of the required work experience for the ASE certs.

Worked in dealerships,worked in the private sector,additional training at the dealership too.

Yadda,yadda,yadda,not like any of that really matters.

If anybody does'nt wanna believe me,go find any text book(s) on the subject,pour over any basic or high performance colling system manuals or such on this topic,talk to any cooling system "experts" whose opinions you trust,talk to sources like those @ Stewart components,their websites tech section has tons of this sorta stuff in it.

stewartcomponents.com

These guys know cooling systems,check out their tech tips and Q&A sections,lots of good tidbits of cooling system info.

Any of those sources that know their "stuff" will confirm/support most all that I had discussed in these threads,I did'nt make the stuff up.

Why would I waste my time BS'ing somebody on a deal like this???

Now that brand of logic really makes no sense...

Anyhow,the cap rating,with a downflow radiator,run the higher pressure cap,the cap is almost always placed on the hot/high pressure side of the system with the downflow radiators,and it's this side that sees the highest ambient pressure spikes,and under continuous higher RPM operation coolant can be forced outta the rad as it expands,this will result in a low coolant level when the coolant is allowed to cool and thus contracts.

On a downflow radiator system,run the highest rated cap you feel your system can safely handle,that will inturn raise the boiling point of the coolant in the system.

Not unusual to see 22 to 24 pound caps on high perf downflow radiator systems,and up over 30 PSI caps on all out racing systems with a downflow radiator,just ask some old shelby mustang/cobra racers this question.

But the cooling system needs to be primo at those pressures!

And maintainance is not optional either!!!

With a crossflow rad,I would'nt be nearly as concerned with the caps rating,it's usually on the cool/suction/low pressure side and thus it does'nt tax the cap as highly as the downflow radiators do.

16 to 18 pound cap on a crossflow system would be fine 90% of the time.

But raising the caps pressure rating will always raise the potential boiling point of the coolant in said system,regardless of radiator type being used.

It's just with the crossflow radiators,most folks are already running to coolant recovery systems,so why tax the hoses and gaskets with excessively high cooling system pressures when you want that coolant to be purged,and then returned to the system when the coolant cools and contracts.

That's one feature you cant employ easily with a downflow radiator (coolant recovery),with the cap on the hot/high pressure side it just does'nt work very well,with this system,the cap is almost always exposed to positive pressure from the cooling system,so it wont be able to effectively draw back in the coolant when the coolant temp drops and the system contracts.

As I said in that other thread,that is why I prefer crossflow radiators.

But I fully understand how to optimize downflow radiators too.

Best thing you can do for a downflow radiator is to add that surge tank I mentioned,it gets plumbed into the suction side of the system and then it gets mounted to put the tank/cap at the highest point in the system,with that one change the downflow radiator can now effectively employ a coolant recovery system too,the coolant recovery gets plumbed into the surge tank now as that is on the suction side of the system as well.

This is the same basic thing you would want to do if the radiator was mounted lower than the engine like was discussed.

In this scenario that makes the actual radiator cap on the radiator redundant,as it no longer is in charge of purging any air or coolant hopefully,and the radiator will usually stay completely full,when you do this,you absolutely would run the highest rated cap for the radiator,as you would only want it to purge in a "meltdown" situation.

The hard part of doing this mod is finding a place in a given engine compartment that's higher than the rest of the system to mount said add-on surge tank,that's because the engineers knew all this too when they designed these cars,so usually they put the cap as high as they could in most instances on these old cars.

Yet very few seem to wonder why that was so...

HTH.

[GT182]

Thanks Bret for the info.... I'm not a certified mechanic but I believe what you say. Never doubt the "ones in the Know" I always say, they didn't go to school to spread BS. And they do know more than us backyard mechanics..... I'll admit that's what I am. But I have learnt a few things from the pros and I'm still learning. Never hurts to listen and learn.

So with that, seeing my radiator is the original to the car, would it hurt if I only went with a 10 or 12 pound cap? I don't want to build too much pressure and chance blowing the core out.... just yet.

[george kujanski]

Haven't thought about the "hose too high" issue yet, but I do know that when filling a cooling system if the air is not allowed enuf time to escape from the top of the engine, (such as putting the radiator cap on too soon), it will overheat and funny things happen such as boiling noises, etc.

This situation easily happens when the radiator top is lower than the top side of the engine such as on my Eldo. The underhood decal specifically states to follow the proper cooling system fill procedure in the manual.

Did it incorrectly once and temp went way up over normal until I corrected it. I knew right away when I saw the temp spike.

George

[screamingchief]

Originally Posted by GT182

So with that, seeing my radiator is the original to the car, would it hurt if I only went with a 10 or 12 pound cap? I don't want to build too much pressure and chance blowing the core out.... just yet.

If it's not purging any coolant past the cap on a regular basis,a higher rated cap likely wont change much in the current situation at all.

All it would do is raise the potential future boiling point should the system start to have issues at some point down the road.

But if you are having issues losing coolant past the cap,yeah you certainly could "creep up" in small pressure increments till you get to a rated cap that will hold the coolant in the engine.

Caps are relatively cheap,so that should'nt break the bank doing it that way.

Could even carry a few spares in the trunk or glove box to deal with any unexpected or occasional situations you might encounter.

You know,one or two lower rated caps if you hafta limp the system home after a make shift repair on the road,and maybe another higher rated cap for when you know your gonna run it harder and are willing to take a chance the system can handle it for a short period like you might encounter taking the car to the track or such.

The primary goal is to purge as much air as possible from the system,and after that the goal is to keep the most effective coolant level in the radiator for the most common operating conditions the system sees.

If the cap rating is too high,it indeed will have a harder time purging air too.

So yeah,a balanced choice is wise.

HTH.

[GT182]

Sounds good Bret, thanks.

I've got a couple caps for spares and I'm going to put the overflow/surge tank in soon.

[screamingchief]

I was talking about this topic with a friend whose opinion I trust well enough,and he told me he's used a recovery system on his downflow rads and said it works very well for him.

Now far be it from me to speak in terms of absolutes,when I said that set-up does'nt generally work well,that was mostly in terms of basic cooling system theory,and not based on practical application,so I would be willing to concede that may be another option so long as there is not a problem with trapping any air in the system in the first place.

He agreed on the trapped air situation,he also added it's a must to use a recovery style cap as well should you try to use the recovery set-up with the downflow rad,but we did'nt get into details on the specific reasons why he felt that way.

I know most caps are designed to permit relief if the system gets deep into a vacuum,but it may be the caps are rated differently as far as what point that will happen with a non-recovery cap vs. the recovery style caps.

I dont mess with downflows if I can avoid them,so I personally wont dispute/argue that specific point here.

My main point here was to suggesting looking at this as a "big picture" scenario,all these things need to be considered,and trapped air is one of the toughest gremlins of cooling systems to deal with,as so few give it much thought.

HTH.

[GT182]

Last night after I signed off I got to thinking.... yeah right. LOL

Could it be that most of us with this overheating problem aren't getting the trapped air out after a new engine install and filling up the radiator? We just add coolant and go, not taking the time to let it sit and work out the air in the system. Just a thought to consider as I know most don't. That could have been my problem, and then it could have been just the upper hose sitting higher than the cap. Makes ya sit and think about it a bit.

[GT182]

Last night after I signed off I got to thinking.... yeah right. LOL

Could it be that most of us with this overheating problem aren't getting the trapped air out after a new engine install and filling up the radiator? We just add coolant and go, not taking the time to let it sit and work out the air in the system. Just a thought to consider, but I know most don't it like that. That could have been my problem, and then it could have been just the upper hose sitting higher than the cap. Makes ya sit and think about it a bit.