i have a problem the overflow is puking half the time. i say half because this happen only in the day. very warm out cars not running hot 195 200 and will maintain this temp. but shut it off and it will puke but not at night lower air temp . tried a 18 lbs cap no luck changed the 195 stat to 160 .no luck still pukes checked timing 38 at 3000 car runs great. would love to try to fix problem with out putting a overflow can on the car. this is a ls5 w/ a ls6 solid lift cam and piston from a 71 ls6 basically a very healthy ls 5 also a new gm clutch fan was installed at the beginning of this problem this motor is new to this car w/ 500 miles trying to work the bugs out. when it dose puke i used a inferred heat gun and the coolant coming out is 187 :confused: thanks ed

Stop refilling the radiator. There's a level that it "finds" on it's own, and assuming there are no leaks it will stay at that level. If the fluid gets extra hot one day, it may come out a little more, but that's how it's supposed to work.

Fluid expands when it gets hot, that's why it's coming out the hose.

However, you really should put the end of the hose in something to catch it. I heard a tablespoon is all it takes to kill a dog - I know it's lethal to animals but not sure at what quantity.

mark thanks for the reply . the level it seeks is about 3 in down from the tank top i was filling it to one inch from the top i will try this level thanks ed

I did the same thing with mine Ed. I kept trying to top it off and it would always puke a little after driving it. Now I leave my level right about the same (3" down) and it's happy and stays around 195 degrees and never pukes.

mark thanks for the reply . the level it seeks is about 3 in down from the tank top i was filling it to one inch from the top i will try this level thanks ed

An inch or inch and a half is what the factory manuals say. I would retrofit a reservoir that catches the hot expanded coolant that has passed the relief valve in the cap. See the many posts here on retrofitting a coolant reservoir. One benefit is you don't make a mess and poison the environment and any hapless critters that may be attracted to the spilled coolant.

Major benefit is the exclusion of air in the system which reduces the rate of oxidation (corrosion) of components like pumps, radiators, etc. Excluding air also excludes oxygen which is the SURPRISE! major cause of oxidation...

thank guys i will try that and i may install a recover tank i just need to hide it cant stand the look of one in a stock Eng compartment . i was thinking in the pass fender be hind the battery

I have been working on thses cars for over 37 yrs and the statement Factory Muscle made about the proper coolent lvl being approx 1" from top of the filler neck is incorrect.

As already stated the proper lvl is approx 3" from the filler neck when cold .

Keeping the proper coolent lvl will negate the small expence and time of installing a puke tank ,why bother installing it if all you have to do is run the proper coolent lvl.

Since you mentioned your running a fan clutch if your running the std duty thermostatic clutch(non ac fan clutch) install a H/D thermostatic fan clutch for the A/C application .

I did this for my mild 69 396 (4 core with hi flow pump & stat with gm 7 blade 772 fan & stock shroud) and it droped the stop/go traffic & slow speed temp approx 8-10 deg on a 95 deg day which was substantial.

The H/D Napa fan clutch i installed on my 69 was pt# TEM271303 for the long bbc pump & it fits the stock gm 7 blade 772 fan used in 69-72 .

The h/d clutch turns the fan approx 10% more rpm then the std clutch when not locked up which is hardly noticeable but cools a little more due to more air being pulled through the rad even when the clutch is not locekd up and you cant hardly hear the difference even thought the fan is turning more rpm when not locked up. But when the motor gets hotter in stop/go traffic and it locks up it turns the fan approx 15-20% more rpm pulling more air through the rad when sitting still and thats where it really helps out.

I just tested it out the other day when it was 95deg /HHH here in NY state and it helped a lot,esp when comming out of a traffic situation where you were sitting still for a while and then getting up to speed again. In that case the motor /cooling system only took a 1/2-1 mile to get back down to 190 deg and then the fan unlocked and things were fine. You can hear the fan is turning more rpm when the clutch is fully locked up but that only happens for a short period of time untill the cooling system temp drops and the fan clutch unlocks. It's the sever duty fan clutches that can really drive you nuts becasue they turn a lot more fan rpm when unlocked and locked then the h/d clutch does.

But with the prior fresh only 2 yr old std duty clutch i had in 95 deg weather it would take 2x-3x longer to get back down to 190 after sitting still and getting up to speed cruisng again then with the new h/d clutch . That's not to mention the fact it also ran hotter in traffic with the std clutch where as with the h/d clutch it ran a little cooler sitting still in traffic on a 95 deg day,it was well worth the expence to swap to the h/d napa fan clutch,wished i had done it yrs ago.

Scott

Allowing for expansion above the coolant level can't cause air in the system since the radiator outlet is at the bottom.

It took me a while to learn to stop refilling the radiator and just let it seek it's own level.

Allowing for expansion above the coolant level can't cause air in the system since the radiator outlet is at the bottom.

It took me a while to learn to stop refilling the radiator and just let it seek it's own level.

Hmmm. I wasn't thinking of air being entrained in the coolant; I was thinking along the lines of the engine block and heads, along with the hoses and radiator, as being "the system" that contains the liquid coolant solution. So it seems to me that the volume of heated coolant, having expanded to fill the entire "container", will subsequently contract as it cools; thereby leaving a space at lower-than-ambient pressure i.e. a vacuum. Seems to me that air will have to be admitted past the radiator cap, or "the system" will be under negative pressure with respect to the atmosphere. I suppose in a vacuum situation, the hoses will collapse, and the radiator might fail, or air might enter the system past the water pump seal.

However air would enter the system; it would be "fresh" air, seems to me. Apparently, oxygen at ambient pressure will diffuse or dissolve into water at room temperature. Ask any goldfish...

Anyway, thats just my $0.02

I installed a polished overflow in my car -- gets lots of complements at the local shows. The can fills from the bottom when the fluid is hot, and will siphon the coolant back into the radiator when it cools. If too much fluid is pushed into the can, it will drain the old fashioned way (to the ground), but I've never had this happen.

Dave

SWHEATON thanks for all that information. i learned i was over filling the rad. and i changed the c fan because it was a older one and non thermal. i changed it to a ac delco 15-4443 and i have been on the fence if it was doing the job . i know you said the sd would drive me crazy but if i can get more from the sd i am in .Fla will boil in July and august and i like that a/c on i found a Hayden #2797 sd $65.00 at advanced . unless you have a p# for napa sd i think i will go w/ Hayden again thank you i really think the problem is this

Hi Ed,you likel dont need the S/D hayden 2797,its a sever dudy thermal fan clutch for h/d truck apps and will be on/locked up too much and will dirve you nuts,too much noise,and will waste more fuel too being locked up more causing more drag on the motor.

Get the hayden H/D 2747 or napa 271303 both h/d thermal fan clutches just right for Hi perf apps,a/c apps,or the H/Duty cooling option offered back in the day.

Both thoses clutches will out perf the non themal cheapo clutch you were running by a mile esp when the motor heats up in traffic so if its not really overheating with the the current non thermal clutch but running on the edge of being too hot then i would think you should be fine with the h/d thermal clutch.

But if you really dont mind the additonal fuel use and more fan noise then go for the sever duty hayden fan clutch because it wlil give you the best/max cooling but at what price in the long run to your pocket & in comfort/noise,thats up to you.

Lastly,a Suggestion,if your unning manual trans idle it a little higher then normal like 950-1,000rpm durring the hot season with the h/d fan clutch so it can do its thing pulling in more through the rad when sitting still with a little higher idle speed.

Scott

Hmmm. I wasn't thinking of air being entrained in the coolant; I was thinking along the lines of the engine block and heads, along with the hoses and radiator, as being "the system" that contains the liquid coolant solution. So it seems to me that the volume of heated coolant, having expanded to fill the entire "container", will subsequently contract as it cools; thereby leaving a space at lower-than-ambient pressure i.e. a vacuum. Seems to me that air will have to be admitted past the radiator cap, or "the system" will be under negative pressure with respect to the atmosphere. I suppose in a vacuum situation, the hoses will collapse, and the radiator might fail, or air might enter the system past the water pump seal.

However air would enter the system; it would be "fresh" air, seems to me. Apparently, oxygen at ambient pressure will diffuse or dissolve into water at room temperature. Ask any goldfish...

Anyway, thats just my $0.02

ALL that would take place above the coolant level in the top tank and the coolant entering the engine comes off the bottom of the radiator where there is no air (unless the radiator was completely empty.)

I'm not saying to leave the level low enough in the top tank to allow it to get below the radiator cores.

scott i order the 271303 napa one to day it should be here tomorrow i thank you for your help i will let you know the out come thank again ed

Ed,NP,good luck and rpt back on how that new h/d fan clutch does as compaierd to the non thermal unit your replacing,i bet it will do a much better job of cooling.

Scott

Mr Gasket makes a very discreet looking overflow. It's under part number 5129.

Ed,NP,good luck and rpt back on how that new h/d fan clutch does as compaierd to the non thermal unit your replacing,i bet it will do a much better job of cooling.

Scottscott i in stalled the clutch fan today and from what i can see its working and your wright the sd would have been extremely loud i can hear the hd one seems to have lug ed the car down a bit but it was in the 90s today and had the a/c going and beat on it a bit and parked it and a few dribbles came out and temp stayed down around 198 when parked they would creep to 224 before lower hose was 168 :hurray:very happy i will pm you later on as time goes on the true test a road trip but feel coffined this was the fix

Hi Ed,glad to hear you got it sorted out.

And BTW,the h/d fan clutch did lug/take the light throttle snappyness away from my mild 396 too when the motor was hot like in 90 deg when the fan clutch was lcoked up.

But i got on it tonight comming home from a cruise and with the peddle to the metal thur a few gears it didnt seem to bother it at all,all the power seem to be there when i wanted it.

You should only feel the fan affecting the motor power when the fan clutch is locked up on a hot day in traffic or with the ac on.

But to me the additional cooling the h/d clutch gives us is well worth giving up a little light throttle snappyness and hearing the fan some when motor is hot and fan clutch is lockes up untill you get rolling again cooling the motor back down in a mile or 2 when things coold down again and the fan clutch unlocks unitll things heat up again.

Let us know how the new h/d fan clutch does on the road trip.

Scott