Cooling System at Startup Help

[harnalien]

Well I finally got my truck to turn over the other day. It sounds strong, but we noticed a major problem with the cooling system. Basically, it seems the pump is not pushing coolant through the system. We took the pump off and it rotates fine and does not have any metal or binding issues. The pump on LQ4's rotate counter clockwise right? I have the belt routed the way I have seen others route theirs. The engine did not have any coolant in it when we installed it. We tried to put coolant in it, but couldn't get an entire jug of in it without overflowing the radiator. We figured that when the motor started, the pump would start to suck and circulate the coolant, then we would just fill it back up. We plan on reinstalling the pump tomorrow and trying to pour fluid directly into the upper water neck so it gets into the pump and engine...kinda priming the system. Does this sound right? The bottom radiator hose had fluid, but the top one was bone dry. Please help me figure this out! I'm hoping it's something dumb I'm overlooking. It's been about 2 months trying to get this thing running. ('04 6.0 into an '84 2wd shortbed).

[TR65]

harnalien,

I am not an expert on this but do you have the steam vent routed to somewhere high on the radiator? Seems like most of my air came out of that vent when I was filling. If nothing else, open it down at the head and see if coolant will go in. I could get most of the coolant in, 3+ gallons as well as I remember, my engine was empty also.

TR

[clinebarger]

Take the upper hose off at the radiator, Turn the hose upright & pour the coolant into the hose, LS & LT engines are reverse flow (The thermostat is on the bottem hose) & the coolant flows bottom to top in the radiator.

[Super73]

Originally Posted by clinebarger

LS & LT engines are reverse flow (The thermostat is on the bottem hose) & the coolant flows bottom to top in the radiator.

The LS is not a reverse flow like the LT. True it pulls the coolant from the lower radiator hose, but it is not a reverse flow. In other words, the coolant flows to the block then the heads, just like the traditional small block. The LT's actually cool the heads prior to cooling the block. LT's are a true rverse flow.


You definately want to fill the motor up using the upper radiator hose trick.

[clinebarger]

GM got sued by Evans over the rights to the "Reverse Flow Cooling system" http://money.cnn.com/magazines/fsb/f...3431/index.htm

And according to the diagram below & everything else ive read....Your right.

BUT...There is a BIG problem with this diagram! It shows the coolant from the radiator flowing through thermostat into the engine. How would that work? The cooler water from the radiator would close the thermostat before all the hot water got out of the engine. If we reverse the flow on the diagram...It would be a perfect example of a "Reverse flow Cooling System" & the thermostat would work like every other thermostat Ive ever seen.

My theory is LS engine are reverse flow...Untill someone explains how a thermostat can operate on the suction side of a cooling system, I stand by what I stated earlier.

[harnalien]

Thanks guys, that's what we were planning on doing tomorrow; pour coolant into it via the uppor hose. I wish I had thought of that before I took the dang pump off. We were sure it was bad.

[68GMCCustom]

I almost burned mine up figuring this out...guess I should have done more reading.
Fill up the radiator only and you don't get coolant into the motor. hmmm...sounds right???

once I poured coolant into the top of the block, the system opened up shortly after and began flowing.

[85burb]

I filled mine up from the rad. and have had no problem at all. Have put over 70 hours on it so if it was not getting coolant it would have died by now. It is 100 degress here to. Interesting tho.

[harnalien]

Got the pump back on, filled it from the top hose and fired it up. Now I've got a leak somewhere. I thought it was from the front drain plug, but it's tight. I think/hope it's coming from the steam line, but I can't tell. I'll have to look at it tomorrow. This is really starting to suck.
Posted via Mobile Device

[Shon]

Originally Posted by harnalien

Got the pump back on, filled it from the top hose and fired it up. Now I've got a leak somewhere. I thought it was from the front drain plug, but it's tight. I think/hope it's coming from the steam line, but I can't tell. I'll have to look at it tomorrow. This is really starting to suck.
Posted via Mobile Device

might have hit the steam line and cracked it..it happens or the clamps used are not working correctly.

[Super73]

You can stand by what you said, but I can tell you from experience, the above diagram is correct. Go pull the upper radiator hose off any LS motor and fire it up. You won't get much if any movement until the T-stat opens. Then you have a fire hose till you run the radiator dry.

This is the very reason that priming the motor with water before fire up is very important (pooring it down the upper hose).

[gopokes]

I'm glad I read this post, the first few times I fired up my engine I had only filled up the radiator, then rechecked the water lever, since it didn't go down, I assumed the engine was full of water already. I filled it this weekend from the top hose, took a little over a gallon. Glad I never let that thing run more that a little bit.

[Super73]

Also double check the o-rings are in the steam line plugs or the surface that mounts the steam line to the heads. If they are there, make sure they are not torn.