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Discussion Starter #1
When I had my engine out for the last time a couple of months back I decided to address the broken exhaust bolt on one of the heads. Turned out the head was fucked so I had to replace.

While at it I did both head gaskets.
Prior to it the engine run like a champ with the same plumbing/rad and so on in my rig,... basically tested to be fine as it was in case something didn't work later...


... guess what...

After having it finally fire again today after laboring through harness mods with my bud Dave for days we run into a weird overheating problem.



Simply put the coolant is not circulating through the rad or the head (heads?).


Thermostat has been replaced as well as (both old and new one) tested just in case - and they open and close in boiling water as they should.
Serpentine belt is installed correctly.... and externally there just isn't anything wrong in any way. Rad is brand new (Griffin) steam port hooked up (as it was in the test fit/run), blah, blah, blah...



Now:
Do I have a vapor lock maybe? How can I tell/fix?

or

Did I mess up (even though I tried to pay as much attention as possible) the head gasket placement and could it be reversed blocking the flow?

I suspect one of these two problems as after removing the temp sending unit from the driver side head (underneath the alternator area) I noticed there is no coolant in that area at all!!! Bone dry!!! This means no coolant in the engine at all, right?


:confused::confused::confused:
 

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I know this is going to sound stupid and may not even apply to an ls engine but is it possible the intake manifold gaskets are on backwards? I have a boat with a 4.3 and the shop that rebuilt the engine put the gaskets on backwards which blocked the water from circulating.
 

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I know this is going to sound stupid and may not even apply to an ls engine but is it possible the intake manifold gaskets are on backwards? I have a boat with a 4.3 and the shop that rebuilt the engine put the gaskets on backwards which blocked the water from circulating.
i dont know if it is like ford small blocks but the gaskets can def be installed backwards.. my old 302 ran for about 3 months with one installed backwards. created a hot spot in the motor. it would get hot quick and ping like a bitch with normal timing. finally took out a ring land on a piston. when i tore it down i realized it was backwards..
it was the driver side head gasket on mine.
 

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Discussion Starter #4 (Edited)
Yes. It's like that.

The head bolts, piston holes and many passages line up (I checked my old H/Gs I have not discarded yet) if you instal it front to back backwards. But not ALL of the passages.

That's what I'm worried about.

Providing there is some "coolant air bleeding trick' I have not heard of in the LS engine family I am inclined to suspect my gasket orientation.

The reason why i'm still kinda confused and asking if there are any other possibilities is because i thought I was actually paying special attention to that orientation when installing. Having messed that up is kinda hard for me to imagine, but considering where i'm at with it now I cannot discount anything anymore - including my own fuck up...


I decided to post the Q here before I tear the whole thing apart again in case there is a "bleeding trick" I missed...
 

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I know this is going to sound stupid and may not even apply to an ls engine but is it possible the intake manifold gaskets are on backwards? I have a boat with a 4.3 and the shop that rebuilt the engine put the gaskets on backwards which blocked the water from circulating.
x2 im not familiar with LS motors but its possible to do on other motors

i had to help my brother redo the head gasket on his 3.4 toy motor after he put the first one on backwards, a couple coolant passages were blocked causing it to over heat.
 

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You can put them in backwards and it will do exactly what you have going on. You can easily check this though by looking at the little tab that comes off the gasket on the side. I'm pretty sure that the tab should be toward the front on both sides
 

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Incorrect head gasket install aside. Need to verify it.
Sounds like you have air trapped in it. Is the top rad hose full of water? The top is the outlet, the inlet is on bottom and houses the thermostat on Gen III/IV motors. So make sure its plumed to rad correctly. Remove upper hose and fill with fluid then reinstall. Were is the steam line hooked to?
 

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Discussion Starter #8 (Edited)
Yes. I am certainly trying to verify air lock before tearing it apart.

I am running a Griffin LS swap rad. Steam port fitting is part of the rad and that's where it's plumbed - right below the outlet (upper) hose.


So you're saying the best way to fill this system is with upper hose cracked open, but still fill through the rad?

Or should I fill right into that upper hose WP outlet?
 

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Discussion Starter #9
OK....

So I went down to the shop (despite being almost midnight) and verified the upper hose was in fact dry as predicted.


I filled the system through the WP using that hose. It took two gallons.

I then cracked that temp sensor open and sure enough a solid stream came out. That was a good sign.


I started the engine and run it for over 20 minutes after it reached operating temperature. I could feel a solid flow through the rad as it was nice and warm evenly....


Looks like I will not be pulling the heads again!!! :)

Thanx!
 

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Discussion Starter #10 (Edited)
Ya.... this morning just thinking about what happened and looking at this diagram it's clear why it vapor locks itself and why either a bleed screw/steam port or opening the hose on top of the W/P would allow the otherwise vapor locked system to flow again.

http://www.pirate4x4.com/tech/billav...red_resize.jpg


What I found educational here - for future tech searchers is the difference it makes when your block is already filled with water vs one that is dry.


When we first test run the engine (prior to head work) the rad was empty as it was new BUT the block was filled at least as high as the top of that W/P outlet.

This in turn had the T-stat submerged in water. When I filled the rad that time I basically... simply ... well... filled the rad only as the rest still had water (important difference).

What that means is that when the engine was started the T-stat was getting warm coolant as designed and the W/P was pumping instantly and causing the so important circulation! and everyone and everything was happy.


With the block completely dried for the head job this was not the case.

The drawing explains it.


The water was poured into the rad.... that's great but it stopped at the bottom as the T-stat is closed. The bi-metal part of the T-stat was in the air on the dry -block side. I don't think the Tstat was even opening as the air alone may not be enough to heat soak the bi-metal.... but I'm not sure)
The design of this system prevents the water from the rad from entering through the bottom of the block when cold tough (closed T-stat) ... for sure.

Conversely the turbine of the WP was also dry. When filling the rad the whole engine and heads were a big bubble of air and the W/P was pumping air towards the upper hose which would disallow the water from the rad to flow down the upper hose when the rad was finally full. A giant vapor lock.


So when I undid the upper hose at the rad and used it as a "nozzle" so to speak to fill the engine through the W/P it submerged the T-stat and the W/p, allowing it to start the circulation when engine was started again.

So to my understanding of that drawing it is important on a "dry" LS to not just fill through the rad.


I may be wrong so please correct me for the 'future tech" searchers but it makes sense to me this way.
 

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Drill a 30 thousands hole on the Tstat body to allow air to equalize.. Be careful.. Too large and on a cold day at low speed the heater will be slow to come up to temp.
 
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