Heater core EXPLOSION.... Water pump bypass hose???

[74Beeper]

So, my Indy small block 440 with a Mod-Man intake did not come with the water pump bypass port drilled/tapped in the intake. I've read several different opinions on this whether it is actually needed. This engine has a high flow water pump and thermostat and sees 7000rpm+ frequently. The other day, I hit 7000 and popped a brand new heater core dumping 2.5 gallons of antifreeze in the passenger floor well. (What a mess)
Im thinking a bypass hose would keep this from happening again. What else does this hose do and what are the benefits of not running one as opposed to running one?

 

[niteshift70]

Sounds like you need a better radiator cap. The bypass hose just keeps a minimum flow through the water pump and heater core when the thermostat is closed. The cap should have relieved the excess pressure WAY before the heater core gave up. Will have to say that the new heater core had quality issues if it gave up like that.

 

[74Beeper]

I was kinda thinkin the same thing on the cores lack of quality.....

Correct me if I'm wrong, but if the thermostat wasn't open at the time to allow flow/pressure to the radiator, then 100% of the pump output would be forced through the heater core if there was no pump bypass. Right?

 

[badlite]

I had the same thing with my 1965 Plymouth 426 street when new. I poped 2 heater cores, before I learned to shut off heat control before running higher RPM.It would hit to high of pressure before radiator cap could release excess pressure. Never had a problem with control shut off.

 

[74Beeper]

badlite, When you say "shut off heat control" what exactly do you mean? Do you have a bypass valve in the heater core hoses like on an A/C car?

 

[bm02tj]

Hydro test the next one at 30psi before you install it

 

[440roadrunner]

I frankly find it difficult to believe that anything except a flawed core and a high pressure cap was the cause. Those pumps "slip" a bunch, as they are designed to do. They are not "positive displacement" by any stretch of the imagination.

It might well be that the heater core was getting "ready" and that last pound or three of differential pressure was the "straw that broke."

 

[74Beeper]

bm02tj...... i like that idea

 

[Moparsmitty]

Just a few thoughts.
I agree that the quality of replacement heater cores leaves a lot to be desired, not only for our older rides, but for just about any application. I haven't been able to find any manufacturer that makes an actual premium quality heater core. I would be more than willing to pay extra $ for a heater core if I knew I would never have to replace it again.
I also agree that the heater control valve in the line to the heater core should take the pressure off of the core if it is closed during high RPM operation. If you are going to be racing or making Banzai runs, shut off the heat just to be a little safer.
I like the idea of having any new core pressure tested by a competent radiator shop if you can, I've had some fairly new cores fail and pressure testing might have saved me a lot of work.
Finally, if you are running the engine hard when the thermostat is closed (engine cold), that's a no no anyway. Good Luck.

 

[74Beeper]

My whole life is full of no no's but the engine was warm when this happened. I'm just thinking maybe the thermostat closed due the fact it was a 180 thermostat and my electric fan switch kicks out the fans at 170.
What is this heater control valve you guys are talking about? Do all your cars have A/C? I know cars with A/C have them but on my 74 which which has no A/C, the only heater control is a door that closes off the heat radiating off the core. There is no way of throttling or shutting off the coolant flow to the core. If i'm missing something here, let me know.

 

[Moparsmitty]

Your Roadrunner probably came stock with a heater control valve similar to this.
http://www.napaonline.com/Catalog/CatalogItemDetail.aspx/Heater-Valve/_/R-BK_6601235_0069211815
I think that this particular valve was mounted on the fenderwell and cut into both heater hoses to control the hot water flow to the core. A previous owner may have removed this valve for some reason. This valve is operated with a cable that goes to a lever in the dash. Some valves are controlled by vacuum. A simple one hose cable operated valve could be used on the hose coming from the water pump to control the pressure. Hope this helps.

 

[74Beeper]

Thanks Smitty...... That link says "Important Information: W/Air Conditioning". I've owned several old Mopars (This one was my very first in 1990 @ 14 years old) and the only ones that have had this valve were the A/C cars. I'm not sayiing i shouldn't have something like this to keep from poppin another core. But I'm thinkin a bypass hose, with a cooler high flow thermostat and a pressure tested core like you guys mentioned.........

 

[nodust]

I thought I would impress my date with a 30mph kick down in a near new 59 Chrysler. Blew the heater core immediately, soaking her feet with antifreeze! I ended up marrying her! One of my best moves!

 

[74Beeper]

I thought I would impress my date with a 30mph kick down in a near new 59 Chrysler. Blew the heater core immediately, soaking her feet with antifreeze! I ended up marrying her! One of my best moves!

Well played nodust......well played indeed

 

[MarPar]

The other day, I hit 7000 and popped a brand new heater core dumping 2.5 gallons of antifreeze in the passenger floor well. (What a mess)

aw that sucks!!! :sFun_doh2: