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Old 09-01-2017, 10:56 PM   #1
pheengurs
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5/8" heater core hose blowing off!!!

okay in my 64 chevy k10, I've got a 70's 010 casting high nickel sbc block, just turned into a 383 stroker, with 2003 gmc 1ton 906 casting vortec heads and intake...

cooling system was a1 before engine swap. old motor was a same 010 block from my corvette, without vortec heads/intake...only change in this setup is vortec heads and intake...

I've started it up 3 times and all 3 times the 5/8" coolant line from pass front intake blows right off the heater core end!!!

Heater core is not blocked...

Not running a thermostat at all at this point...

My heater core hoses run from front pass intake 5/8" to 5/8" on heater core
Other line runs from 3/4" off top of water pump to 3/4" on heater core...

because I have vortec heads, and all this conflicting info regarding bypass hoses...I don't have anything else... is my hose blowing off because I don't have a bypass hose?
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Old 09-01-2017, 11:54 PM   #2
bpmcgee
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Re: 5/8" heater core hose blowing off!!!

Try putting in a thermostat?

Just thinking that the coolant line blowing off is too much pressure -- maybe without a thermostat to restrict the flow, the water pump is pushing too hard?

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Old 09-02-2017, 12:21 AM   #3
pheengurs
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Re: 5/8" heater core hose blowing off!!!

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Originally Posted by bpmcgee View Post
Try putting in a thermostat?

Just thinking that the coolant line blowing off is too much pressure -- maybe without a thermostat to restrict the flow, the water pump is pushing too hard?

B
worth a shot! i've never actually run without one before, I just wanted to this time as I have all new hoses and a new block heater, and also running just water so that if there was a leak, it wouldn't leak paint killing coolant...

you would think tho, that there would not be much pressure difference with or without a thermostat ???

I dunno I'm at a complete loss...
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Old 09-02-2017, 10:05 AM   #4
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Re: 5/8" heater core hose blowing off!!!

Did you get all of the air out of the system? Air gets compressed under pressure causing things to "let go" . ( You should see a swimmimg pool filter blow its top when the tank is full of air). Water on the other hand is pretty darn tough to compress.
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Old 09-02-2017, 11:51 AM   #5
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Re: 5/8" heater core hose blowing off!!!

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Originally Posted by AcampoDave View Post
Did you get all of the air out of the system? Air gets compressed under pressure causing things to "let go" . ( You should see a swimmimg pool filter blow its top when the tank is full of air). Water on the other hand is pretty darn tough to compress.
usually when pouring fluid into the rad, when it gets near the top, I listen for the bubbling then slow the pour till it reaches the top, let the bubbles go until they stop and the fluid level lowers and keep filling a little bit at a time until there's no more bubbles...

the other way I've tried is running with the rad cap off, for a few minutes to let it pump then seal it up...

have you had a coolant hose pop off due to air in the system before??
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Old 09-02-2017, 07:42 PM   #6
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Re: 5/8" heater core hose blowing off!!!

With out the thermostat in there it is going to get hot. Water goes through to fast and lots of air can stay in the system. What causes the high pressure is water turning to steam. Put a thermostat in it and refill the system. Should work better after that.
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Old 09-02-2017, 07:48 PM   #7
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Thumbs up Re: 5/8" heater core hose blowing off!!!

Quote:
Originally Posted by pheengurs View Post
usually when pouring fluid into the rad, when it gets near the top, I listen for the bubbling then slow the pour till it reaches the top, let the bubbles go until they stop and the fluid level lowers and keep filling a little bit at a time until there's no more bubbles...

the other way I've tried is running with the rad cap off, for a few minutes to let it pump then seal it up...

have you had a coolant hose pop off due to air in the system before??

FIRST
, & I'm guessing most likely: You sure you have accounted for REVERSE FLOW water pump?

SECOND: You may wanna try this after taking care of the first thought above. You'll first need to drain your system completely--but w/no anti-freeze, it won't be costly. Years ago, a great mechanic and close friend stopped me when I was fixing to put water in a fresh rebuild as I was heading to radiator. Told me to take the heater hose loose at heater end, leave cap off rad., and use a funnel to fill system thru that upper end of heater hose. Then when water rose to radiator neck level, had me reconnect heater hose and call it filled WITHOUT any entrapped air. Changed my method from that day forward.

YMMV, but it would at least eliminate one possible cause of your trouble. HTH, Sam

Last edited by luvbowties; 09-02-2017 at 07:57 PM. Reason: more info
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Old 09-03-2017, 03:00 AM   #8
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Re: 5/8" heater core hose blowing off!!!

Drill a 1/8 hole in the thermostat, it will get rid of the air problem. Make sure your fittings and inside of the hose are clean before assembly and use good quality clamps.
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Old 09-10-2017, 11:50 AM   #9
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Re: 5/8" heater core hose blowing off!!!

alrighty, todays the day I tackle this problem...

thanks for all the replies and advice!

I'm probably wrong about the year 1ton chev truck I salvaged the heads from... thought it was an 03, but most likely was a 93, as I've read elsewhere chev changed it's motors again after 96? anyway, the heads are indeed 906 casting vortec, worked by D&W engines in calgary to accept the comp cams xtreme 4x4 x4270h cam .480/.498 lift @ 107 centerline...

so I'll put the thermostat in. I already tested it on the stove in a soup pot with my infrared gun, it is a mr gasket hiflo/nofail 180F, and opens at roughly that...

the waterpump is the same 70's long neck that was on previous motor, and pulley is a smaller chromed one, but was also running on old motor... as I understand it, only newer blocks that have serpentine setups have the possibility of a reverse flow pump ... thankfully I don't have to worry about that problem...

as for the air situation -- I agree, one will never be free of air in the system, as it is not possible to purge it all... one would think setting some kind of bleed valve or something at the highest point of flow, would do the trick???

for my truck that would be the 5/8 hose fitting that keeps popping off... every other point in the system is lower including the rad cap...

I added 2 pics of blowout aftermath #2 & 3 and one of the engine bay just beforehand...

the 3/4 hose connection I lathered in copper rtv as it was my first hose installed with these rpc hoses, and I did not trust the connection. (I did not RTV any further ones as they seemed to fit better)
it's clamped to a copper tube, no bumps on it, but the tube itself is long enough to contact both the flex hose inside that fitting as well as the tubing coming out of the heater core, so there is next to no pressure on the fitting hoses at all...

the 5/8 hose connection that keeps popping off, was first copper tubing with bumps (no pic of it sorry) second and third blow offs were this PEX house plumbing fitting, that in the second pic, you can sorta see has barbs albeit small ones, and the clamping surface of each side is roughly only that of a hose clamp wide... I've tried finding longer, but it appears 5/8 fittings are going the way of the dodo up here...

ever since nascar went to efi, the carbed sbc market has gone to the dogs...

first pic you can clearly see the inner sleeve of the RPC kit failed -- second pic the sleeve held but surely began sliding out of the outer sleeve before popping off... -- third pic demonstrates how that 5/8 hose connection is the uppermost portion of my cooling system...

I will an extra hose clamp in between the polished fitting and the hose end, and install the thermostat = if this holds, I'll be a happy guy. if not, my only other idea would be to buy some copper tubing and bend it myself, and try to swage? the ends somehow to get the bumps...
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Old 09-10-2017, 12:25 PM   #10
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Re: 5/8" heater core hose blowing off!!!

If it were mine:

- run a stock thermostat, no drilled hole (if it needed it, GM would have drilled a hole)
- get the cobbled together fittings and metal hoses off of there, and run straight rubber with one good stainless worm clamp on each end

I bet the hoses will stay in place.
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Old 09-10-2017, 12:41 PM   #11
pheengurs
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Re: 5/8" heater core hose blowing off!!!

Quote:
Originally Posted by jayoldschool View Post
If it were mine:

- run a stock thermostat, no drilled hole (if it needed it, GM would have drilled a hole)
- get the cobbled together fittings and metal hoses off of there, and run straight rubber with one good stainless worm clamp on each end

I bet the hoses will stay in place.

yeah, that's sort of an option... the reason for the oddball setup at the heater core is because the only replacement I could get at the time was missing the extra bends that a stock one has...
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Old 09-10-2017, 08:12 PM   #12
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Re: 5/8" heater core hose blowing off!!!

Toss those hoses and get some regular hoses as stated above. Post some more pics of the front of the truck. You say in the first post it is a 64 but lots of stuff looks like non 64 to 66 parts.
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Old 09-12-2017, 10:53 PM   #13
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Re: 5/8" heater core hose blowing off!!!

UPDATE: yes indeed folks, putting the thermostat back in seems to have done the trick. I did add an extra hose clamp to the middle of the 5/8 fitting, lightly tightened just to help the hose adaptor keep it's shape under pressure...

I only ran it long enough to have the efans cycle on once .. and I can tell you I was pretty jumpy keeping a wary eye on that damned 5/8 hose fitting, while wearing a face shield and full welding leathers...

I'm very happy it did not blow off...I spent a hard earned $90 cdn on those damned flexible hoses ... to me it's not like I cheaped out... for that price those hoses should be idiot and bullet proof !!! then again, I'm over the hill, and still think a loaf of bread, container of milk, and a stick of butter should cost under $5...

I will however take a closer look at making my own 5/8 - 90 degree elbow pipe fitting, or perhaps, if its possible, to change how the heater core is mounted in it's box there, so that instead of it's fittings sticking up, they would stick downward, through new holes cut towards the engine rather than away from it... if I do go that route I'll post up a how to of such butchery...


thanks again all for your expertise!!!


and oh ya this truck is far from stock...she is a mishmash of chev parts, for sure...

the p.o. did all kinds of things to it. most notably, the entire front body (hood/fenders/grille etc) is a fiberglass flip front, that has a 63 grille and headlight assy...

-several body parts modified to seal up the wiper/firewall/drainage area I think

-radiator core support is from a 71 chev according to the stickers n stamps

-front frame hacked up to support the flip front fiberglass hinges...

-fishplated driver front frame standard for power steering gearbox upgrade

-radiator I installed out of a 93 suburban, recored from 4 core hi efficiency down to a 4 core, several years ago...

-efans are out of a 6cyl 99 contour (boo! ford parts on a chevy! but those fans draw less than 15 amps together, and are reliable. but when they do fail, I'll grab some dual efan setups from late model impalas or something chevy related)

-brake master cylinder I upgraded a few years back after the stock closed knuckle gave up the ghost. front axle is now a dana 44 with disc brakes.

-wiper washer pump and resovoir I installed from an 80's chev

-engine of course is not stock, as mentioned, its a freshly built 70's gen 1 block, hei ignition, vortec heads 383 stroker...

bucket seats are out of a 99 tahoe...

inner fenders are probably from a 67-72...

tires are 33x15x12 mud country

frame/engine mounts/trans/tcase/rear end/steering column are all stock... I'm pretty sure I've posted the specs on this truck on this site before ... but if you are really bored, here's my inital build post on my buds local forum:
http://www.bomp-bomp.com/forum/viewtopic.php?f=4&t=604
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Old 09-13-2017, 12:10 AM   #14
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Re: 5/8" heater core hose blowing off!!!

If you would simply get the correct heater core, you wouldn't have all that conglomeration of hoses and fittings.
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Old 09-13-2017, 12:57 AM   #15
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Re: 5/8" heater core hose blowing off!!!

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If you would simply get the correct heater core, you wouldn't have all that conglomeration of hoses and fittings.
oh Captain! that's just simply too easy a solution! well, on paper anyway...

lmc has them at 70-80 bux us .. doesn't seem so bad right? well, that's actually closer to 110 cdn after conversion, and related fees.. not to mention another thirty bux shipping up here to canada. so now i'm looking at 140 bux...

for that kind of money I could prolly pay a rad shop to refurbish and extend the piping any way I'd like...

I believe I replaced that heater core around 5 or so years ago, and I've been using that same ugly but functional setup since then... I'd have to go back to my reciept pile, but either Napa or LMC placed that correct size but wrong fitting heater core in my hands... I dunno why I didn't fight to get the correct one, but I'm stuck with it now, until it fails...completely...
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Old 09-13-2017, 05:44 AM   #16
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Re: 5/8" heater core hose blowing off!!!

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Originally Posted by pheengurs View Post
oh Captain! that's just simply too easy a solution! well, on paper anyway...

lmc has them at 70-80 bux us .. doesn't seem so bad right? well, that's actually closer to 110 cdn after conversion, and related fees.. not to mention another thirty bux shipping up here to canada. so now i'm looking at 140 bux...

for that kind of money I could prolly pay a rad shop to refurbish and extend the piping any way I'd like...

I believe I replaced that heater core around 5 or so years ago, and I've been using that same ugly but functional setup since then... I'd have to go back to my reciept pile, but either Napa or LMC placed that correct size but wrong fitting heater core in my hands... I dunno why I didn't fight to get the correct one, but I'm stuck with it now, until it fails...completely...
He's right. I worked up there for a long time, the CDN citizens pay fees for American goods and they have a ministry of (you name it) charging fees as well. I had a friend there go down to US and buy all kinds of car stuff. Removed all the packaging and threw the parts in the pickup bed. When he crossed the border into Canada he told them it was all used parts and they didnt charge him a fee for them. Poor guys. Super glad you got it worked out.
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Old 09-13-2017, 12:05 PM   #17
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Re: 5/8" heater core hose blowing off!!!

Congrats! Great news.
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Old 09-14-2017, 09:15 AM   #18
pheengurs
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Re: 5/8" heater core hose blowing off!!!

ya it's brutal up here... and I believe our govt here passed laws recently forcing online retailers to charge canadian buyers the canadian sales tax, even though the previous laws said it didn't apply to foreign goods, the new law says it does now...

so tack another 7% onto whatever canadians want to purchase from our brothers down south...

almost like they don't want us to buy speed parts!

that tea party y'all had down there awhile back, sure sounds like a good idea!!!
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Old 09-18-2017, 09:28 AM   #19
pheengurs
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Re: 5/8" heater core hose blowing off!!!

one last further update relevant to this thread:

as of this saturday, I also found out why the headers were glowing and why the cooling system was having such a difficult time doing it's job (in addition to previous mistakes!)

spark plugs.

that's right. spark plugs. Napa sold me Champion R17YC instead of the universally recommended AC Delco R44LTS plugs, for higher compression gen1 SBC with vortec heads...

the champions they sold me were not only the wrong heat range but a 1/2" long thread instead of 3/4"

my guess is because the spark was initiating partially inside the threads of the head, the head tried to soak up too much heat and the same for the exhaust side of things...

hence the lean looking condition of the plugs and the center of my block huggers glowing red hot, and coolant boiling all over the bloody place...


Saturday I installed the Delco R44LTS plugs which are 1 heat range colder than stock (?) and on this and many other forums supposed to be one of the plugs choices to use when running betweeen 10.4-12:1 compression.
(I'm currently running at 10.6:1)

The truck did not overheat, the cooling system functioned flawlessly, and I was able to fiddle with timing and mixture without fear for the first time with my new engine...

so if you have the above issues, make sure you are running the correct plug for your application, because it can cause all manner of other unforseeen problems!!!
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Old Today, 03:58 PM   #20
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Re: 5/8" heater core hose blowing off!!!

To bad you had to get rid of your purty hoses. Glad to here you fixed it some people dont come back on here to tell us what was wrong.
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