wierd cooling system problem noise ?

[sweetk30]

so i have the brand new gm L31 engine in my 1987 truck with a edelbrock rpm intake with the 1988-95 style water pump for reverse rotation for serp belt . my heater core feed is intake front right / return rad pass tank top nipple . i have a 195*t-stat with a pin hole drilled in it for burping air as the t-stat with the dingle thingy was 20 bucks more no thanks . rad is a 3 core copper/brass unit for 1981-1991 square body with hd cooling . has a factory shroud on with factory hd fan with thremo clutch that works good .

truck runs 195*-200* all day no problems . tons of winter time heat in the cab no problem . no leaks on the floor from bad heater core .

i was smelling coolant and have checked it 3-4 times no leaks . no loss of coolant . overflow jug is spot on cold line cold and up a inch or so from cold when up to temp.

i notice a growling almost low decibel air horn sound when the t-stat has opened and then i smell coolant . it looks like the system is pushing out the rad cap and in to the overflow tank and sucking it back in . but when i pushes it in the overflow i am getting the hot coolant smell in the cab .

as i said i have not lost any coolant / the rad is to the tip top / overflow working as it should receive and give back .

is there something i missed or did wrong on the system i put together ? or do i just have a super weird weak pressure cap (16psi ) ? or do i need to pull a little coolant from the rad and give a small air bladder of room to keep it from pushing in/out all the time ?

thanks for any help guys have a good day .

[truckster]

Did you replace the cap? That's where I would start.

[sweetk30]

have not yet . this rad and cap combo worked perfect on the truck i just scrapped out due to severe rust from a hard life .

i know a caps cheep . i will get one . just figure post up and see if its not just my weird luck .

[SunSoaked]

I have the same setup. I'd blame it on the Sniper.

[sweetk30]

Originally Posted by SunSoaked

I have the same setup. I'd blame it on the Sniper.

ha ha ha thats a whole other thread for sure .

[sweetk30]

update : so i still get the weird noise and coolant smell . i stopped and got a fresh bottle of block test fluid from napa since my old bottle went bad . i tested the system warm and not 1 bubble up threw and fluid never changed color .

so i called the dealer i got the engine from and he gave me the gm tech line # to call . so i called and talked with a guy and he was a fellow square body gm truck owner so he knew just was i was describing .

i told him i have supply for heater core from intake to core then return from core to upper nipple on rad tank .

he said that's fine for the older stuff NON vortec head engines . but the way the vortec heads flow water inside its starting to boil the coolant and form gas / air bubbles and this is were i am getting the sound from when i bypasses the rad cap and in to the overflow .

he said try this and it should fix my problem . hook the nipple to the h2o pump top port and feed the heater core . then return the heater core to the intake crossover port .

so i guess i will drain some fluid off and re-route my lines and give this a try unless this dosn't make since to you guys .

i told him i had it hooked up the way my old tbi engine was basically plumbed and he said nope the vortec head flow a bit different .

[garyd1961]

The port on top of the water pump is an intake port. It draws water through the heads when connected to crossover on front of the intake.
I have said this a many times on here that if all motors were plumbed this way it would eliminate most of the heating problems people have.
People will buy bigger radiators, high volume water pumps, electric fans, but will not run a cheap hose from the intake to the water pump.

ETA, Vortec heads are lighter and thinner which makes them more prone to heating and cracking.

EDIT #2, When you have a by-pass hose running from the crossover on the front of the intake to the water pump (whether running through the heater or not) it keeps the water moving through the heads so it doesn't have time to boil. The water goes from the pump through the block up through the heads and back to the pump, it does not go through the radiator. The water circulates through the motor like this all the time even before the thermostat opens. This way the motor heats up evenly and steadily until the thermostat opens. Even after the thermostat opens it keeps a steady flow of water through the motor.
Even if you are running the non-vortec motor it's still a good idea to plumb it this way.

[SunSoaked]

[Captainfab]

Big blocks with the short water pump have a hose like that as well as small block truck engines and some performance small blocks on the '60's. I agree that it would be a good idea on many different small blocks. I would have to look at one again to refresh my memory but I believe the L31 Vortec originally came with a hose connected to the water crossover, and to the water pump?

Edit: Here is some interesting info. https://www.hotrodders.com/forum/199...-o-443705.html

Originally Posted by garyd1961

The port on top of the water pump is an intake port. It draws water through the heads when connected to crossover on front of the intake.
I have said this a many times on here that if all motors were plumbed this way it would eliminate most of the heating problems people have.
People will buy bigger radiators, high volume water pumps, electric fans, but will not run a cheap hose from the intake to the water pump.

ETA, Vortec heads are lighter and thinner which makes them more prone to heating and cracking.

EDIT #2, When you have a by-pass hose running from the crossover on the front of the intake to the water pump (whether running through the heater or not) it keeps the water moving through the heads so it doesn't have time to boil. The water goes from the pump through the block up through the heads and back to the pump, it does not go through the radiator. The water circulates through the motor like this all the time even before the thermostat opens. This way the motor heats up evenly and steadily until the thermostat opens. Even after the thermostat opens it keeps a steady flow of water through the motor.
Even if you are running the non-vortec motor it's still a good idea to plumb it this way.

[SunSoaked]

Here's a much better link than the one mentioned above. It's actually factually correct and explains the why & how instead of a bunch of uninformed opinions. That said, it compares the old vs new cooling system designs. Warning: You will want an Lt1 after reading. Lol
https://www.corvetteforum.com/forums...peratures.html

[sweetk30]

so dumped the coolant down below the h20 pump level and flipped the hoses around like the GM corp tech guy said to do .

added a 1/2" pipe thread to 3/4" hose nipple to the h2o pump top port location.
then the 3/4" hose to heater core.
5/8" hose out of heater core to 1/2" pipe thread 5/8" hose nipple on intake front right corner.
then i filled / burped / topped off the system for around 15min and a few t-stat cycles.

i noticed before the test drive a lot less micro size bubbles in the rad tank with the cap off. i also still had lots of heat maybe even a bit faster ? ?

road test i smelled a few hints of coolant but i figure its some i didn't get rinsed off and maybe a few air bubbles working there way out of the system. i spent prob around 20 min driving it the normal way it would do its noise and massive smell before with i would say about perfect results. time will tell if this has fixed it as i still need to get the engine bay dry and no extra coolant on stuff from the work i did .

will report back in a few days with the status of the fix. . . .

[garyd1961]

Originally Posted by sweetk30

so dumped the coolant down below the h20 pump level and flipped the hoses around like the GM corp tech guy said to do .

added a 1/2" pipe thread to 3/4" hose nipple to the h2o pump top port location.
then the 3/4" hose to heater core.
5/8" hose out of heater core to 1/2" pipe thread 5/8" hose nipple on intake front right corner.
then i filled / burped / topped off the system for around 15min and a few t-stat cycles.

i noticed before the test drive a lot less micro size bubbles in the rad tank with the cap off. i also still had lots of heat maybe even a bit faster ? ?

road test i smelled a few hints of coolant but i figure its some i didn't get rinsed off and maybe a few air bubbles working there way out of the system. i spent prob around 20 min driving it the normal way it would do its noise and massive smell before with i would say about perfect results. time will tell if this has fixed it as i still need to get the engine bay dry and no extra coolant on stuff from the work i did .

will report back in a few days with the status of the fix. . . .

Glad to hear you got it straightened out. If you have a temp gauge you probably noticed it runs more even, not jumping all around.
Another thing there is no need to drill a hole in your thermostat when plumbed like this. Air bubbles can't get trapped behind the thermostat because the water is constantly flowing through the motor.

[garyd1961]

The flow is basically the same for vortec and non-vortec engines except for the water pump by-pass on the non-vortec motor. With the non-vortec motor with the heavy cast heads and 195-250 hp the pencil size by-pass in the water pump was a plenty to keep things cool. If you bore it out(thinner block) raise the compression and hp you need more flow to keep the heads cool. If you add vortec heads without the by-pass hole you definitely need a by-pass hose.
I don't think the head gaskets have anything to do with it unless you get into the small block 400 with steam holes in the heads.

[sweetk30]

well the truck has sat for 2 days out in the cold . its 27* out today .

i fired it up and took it out for a trip to the local quicky mart store 3 blocks away . i left it running when in the store for 2 min time . drove the truck home and left it run another min or 2 and when i shut down the truck i was at around 120*F temp range on the digital temp of the efi unit .

few hr's later i go out side and walk past the truck and spot coolant on the ground under heater core area ? ? ? pop the hood and i have no coolant in the jug / rad full and dead cold / coolant has leaked past the heater core 5/8" hose at the core & the radiator hoses all points and i even have a puddle on the intake just off the side of the t-stat hose area .

this was fresh from todays run as the truck is now backed in the same spot and fluid all coming from were it is now .

i think i have a big cooling system problem ! ! !

i cant win with this dam thing .

[SunSoaked]

Mine was pushing coolant past the water neck o-ring only on startup when it was cold and on high idle. The. Bypass hose I added fixed that issue.
Bypass your heater core and add the bypass. If it stops leaking you know you need a heater core.
The other issue is those hubcaps! Take them off and send them to me .

[sweetk30]

heater core flows good / tons of heat / 15* drop 1 hose to the other .

it was leaking from almost every joint it could when i found it and it has NEVER leaked like this before .

got to do a pressure test tomorrow aspr GM tech line and see what she has going on .

[sweetk30]

well pressure tested to 20 psi found a few clamps loose . . . snugged them up and they stopped leaking . must have been heat cycling that got them as they were tight before .

then i left for a parts run in the other vehicle i can use if i have to . left the system for 1:30 time at 20 psi come back at 16 psi and tiny puddle on floor and you guessed it heater core area is damp . . . not sure if its the core tho as the 5/8" hose was one of the leakers before and maybe it pushed in to the cab side before leak outside ? ?

going to dry it up and re-test the system for the heater core area .

this was all done with 55*F shop temp and truck inside for over 12hr's at this temp .

[garyd1961]

Changing a heater core is quite a job but it's one of the best improvements that I have done to my truck. The thing is I never drive my truck when it's really cold outside but on them cool mornings that heat really feels good.

[sweetk30]

ah they aint that hard to do . done my share of them . this one is just a a/c box so a little more work is all .

found a copper/brass new old stock . going to return the newer aluminum style monday .

[sweetk30]

so no leaks at the heater core i can see now . i think it was pushing past the hose clamp and shooting in the cab . but i did find a old stock copper brass heater core and its on its way just incase .

but she still is pushing some fluid and possible gas/air/??? in the over flow but not near as bad as before . i mostly smell it a little bit .

at some point i am going to remove the ecm temp sensor from the vortec bypass port some guys us and some dont and re-plumb my setup to go water pump to intake center just under the t-stat and then heater core not sure yet . maybe back to the original way i had it intake to heater core to rad . . .

and i have a 195* t-stat in the engine . anyone think i should maybe drop down to a 180 range unit ? maybe this engine just wants it a little cooler than 195*

found this searching the internet . its a gm master instructions packet .

Any small block engine, regardless of year, that uses Vortec heads, will require an external coolant bypass line from the intake
manifold to the 5/8" hose nipple on the water pump (passenger’s side). Suggested routing is from the 3/8 NPSF boss on intake
manifold to the water pump.

and the whole thing is here. https://www.chevrolet.com/content/da...e-19210007.pdf

[The Rocknrod]

I'd like to see a picture of that. First time I've read that. I just looked online and saw a few pics (not big blocks) and wonder, how do you hook up the heater core if your using the passenger side pipe fitting on the intake for the bypass to the water pump? - https://www.bing.com/images/search?q...27E8A34024B1BA

[sweetk30]

2 edelbrock intakes . 1 carb and 1 pro flo 4 efi . note the black plug or open port just under the t-stat location . the hole inside is restricted just about the same size as the 3rd hole on older blocks were the bypass port is for the water pump area .

but what has me wondering is it wroth the time to swap around is why wouldn't the heater core routing i have now that gm said to try be the same or better / more flow ? current is h2o pump nipple to core then core to intake crossover port right side next to head .

[The Rocknrod]

I found a GM water pump that is used for vortec head engines and see that it has the upper bypass port.

[sweetk30]

my setup takes long pump / reverse rotation / and HAS the plug port in the top like that one .

[garyd1961]

Originally Posted by sweetk30

my setup takes long pump / reverse rotation / and HAS the plug port in the top like that one .

So you are using a serpentine set-up. If so are you sure your water pump is reverse rotation, I've heard of them boxed wrong from the factory.