Question for engine experts - bypass hose off the water pump

I may have overlooked something in my engine rebuild. In an effort to reduce the plumbing on the front of the motor, I think I've eliminated an important internal byp*** circuit for the cooling system and need to know if it's a BIG problem or not.

On my little GM 3.8 V6, there was a small, internal water p***age in a casting that connects both water heater hoses to the front of the block and water pump. This casting also mounts the alternator. I had the bottom water p***age on this casting machined away to get more room up front and in the process opened up this formerly "hidden" byp*** circuit. Anyway, looking at it now I think this byp*** might be important to the proper operation of the thermostadt and perhaps relieving any undue pressures at the water pump when the thermostat opens and closes...

Problem? GREATLY appreciate any advice / insight into this little circulation pattern. Worry? No worries? Thanx, Gary

 

Some pictures would help.

 

Doc,
I thought about posting one earier, but since the 3800 isn't an SBC or flathead I was posting more along the lines of general principles than specific parts. As requested, here is the only pix I have of that area. The casting that holds the alternator / water lines is one piece. These parallel p***ages run at a slight angle and one is located directly over the other. The upper p***age is connected to the block via an elbow in the blower intake manifold and the lower p***age line is connected to the water pump. The two fittings just to the lower left of the alternator are for the hoses that lead to the heater.

Inside the casting in qustion is that "hidden" byp*** circuit between the two p***ages. So... since we machined away the the lower p***age, there is no longer a connection between the two heater hoses.

Help? Gary

 

I think what your saying is that the p***ages that seperate the heater lines in the casting where machined and are now a single p***age?
Would this not be the same as if you had run a hose from one heater pipe to the other like what people do when they disconnect a heater from a car?
If this is the case then the only problem i can guess is getting a air lock in the system. Those motors can sometimes be hard to bleed from memory theres 2 bleed ******s.

 

Doc,
the upper p***age remains, the lower p***age was removed and that "line" will be replaced by a rubber hose that is routed in a slightly different manner. The heater will still be connected normally. Only the byp*** circuit between them (sort of a permanenly open shunt around the water pump?) has been lost.

Gotta get to work on the 27 now, so I'm signing off - jak at you guys later. Gary

 

Ok, I think I have a handle on it. Sounds like you are pretty much re-doing the way it was only without the byp***.
I cant see it being a big issue, the worst may be like Docco said, air locks. I think these are pretty much the same as the Holden V6 we get. If so the bleeding can be a *****! You may want to add another bleed valve for safety.
Doc.

 

Dont know much about your particular engine but on what few cars I do have T stats in I drill a 1/4 hole on each side of the t stat. This does the same thing as a byp*** hose and allows water to flow in the system until it opens up. On my FE motors I do the same thing and remove the byp*** ****** in the intake and braze the watet pump ******.By p*** hoses are a pain and seem to break at bad times when the decide to rupture and spew antifreez all over the motor ans under hood.

 

Maybe someone else can chime in as well but i think if it was me i'd get it running and the air bled and watch the temp. If she gets too hot you know why.

 

I can think of at least one example where the same block has a byp*** on early versions while later have the byp*** plugged.
I can only see it a hang over from a time when cooling systems and water pumps were far less reliable.
I tend to plug them and can't say I have had any problems as a result.
One 3/16 hole in the stat seems to work fine for letting the air out when filling the system

 

The symptom that will be found is during warmup, the temp gauge will rise to over 200F and then the thermostat will finally open. Not real healthy.

The holes in the thermostat are ok for byp***.
But you said you had a heater hooked up. If you leave the flow through the radiator that will provide byp***, as long as all plumbing and heater core are flowing correctly. 235 Chevy sixes do this.

 

Appreciate the thoughts.... sorry I've been too busy to get back to the HAMB. Right now I'm thinking of taking the safe route... to drill and tap the upper casting / heater p***age that remains for a pipe thread and "replicate" the old byp*** with a small rubber hose to a T in the rubber hose that will replace the lower water p***age we milled off. Gary

 

I can see a problem IF this is a "reverse" flow cooling system. Also the later model cars/trucks have a different style theromstat. It may not work properly with the modified system. However, an old style thermostat may fix any cooling problem.

 

Since where I live is mostly hot weather, I think in terms of ultimate cooling system efficiency. In this vein it would be better to do away with the byp*** and just drill the thermostat (the two 1/4" inch holes) to act as a byp***. That way you don't have the seemingly minuscule amount of hot water not going through the radiator once you are up to temp,a longer warm-up period is the trade-off. Also, leaving flow through the heater core when not being used is a source of interior heat which is not needed here for at least 8 or 9 months of the year, so I prefer a manual (or cable operated) shut-off valve.

 

I ended up adding two "Ts" in the water heater lines at the front of the motor and connecting them with a 1" pipe to establish the byp*** again. I haven't started it yet, but we will get to that by this weekend, I hope! Thanx for all your inputs, Gary

 

As an update on my engine cooling saga... we've got the engine running now and is one cold mackerel. Even with the byp*** I added back into the heater hose loop (replicating the one I machined away), the thermostadt (an OEM item probably at 195F but I'm not sure) takes for ever to open - at least 10 minutes at idle in mid-60F OATs). The water temp gauge just s***s there and when it finally opens, the gauge zooms to about 205-210F and then drops quickly right back to about 180F or so. I find it hard to beleive this motor will run that long without boiling the water trapped in the block and popping a hose or something. But so far... no problems.

So, I'm stlll a little leary about the whole design and at the next oportunity I lthink I'll remove the thermostadt and try drilling a couple of the small byp*** holes in it some of you have recommended. I really don't mind having a cool running engine, but this is just crazy.

Any other idears? Thanx, Gary

PS... the seats are in, the carpet is laid, the dash is nearly wired, the ****** transmits and the AirRide is holding air just fine. We just might get my little truck zooming around the parking lot today!!! Film at eleven.