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STS
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Discussion Starter #1
So I had to change the radiator out because I hit a huge rock on the interstate. Insurance paid $2400 after my deductible so I just ordered all the parts myself and did the work myself. Plus they wouldnt pay for the upgraded 2008+ front fascia anyways.


So I changed the radiator using the instructions on GM techline that I have. Everything went fine but after I filled the rad with coolant (slowly through the expansion tank) I let the car run at 2K RPM until it warmed up then let it idle for a couple mins. Then I topped off the coolant.

Problem is (or maybe it isnt a problem) there is no pressure in any of the rad hoses. The engine is not overheating. I checked with the scan tool and the coolant temp stays around 200 degrees. I have ran the car for 2 days now and it never overheats but even after the T stat should obviously be open there is no pressure in the hoses.


Is this normal? Any help is greatly appreciated.


Thanks
 

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STS
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Discussion Starter #3
Thanks


When I take the expansion tank cap off I can hear it un seal and some pressure come out. Kinda hard to word but hope you know what I mean. It seems to me like there is some pressure in the expansion tank but just not in the hoses. I have drove the car for almost 3 days now and it never overheats and my scan tool says the coolant temp is 199-204 degrees.
 

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2005 STS Northstar RWD
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Are you checking the pressure on the hoses after you open the expansion tank cap? I'm in the process of flushing the coolant, and finishing putting the hoses back on, I can't think of anything that would prevent pressure build up.
 
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Sounds like the vent hole in the cap is plugged. Should not be pressure in the expansion tank.
 

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2006 STS V8 1SF RWD
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EChas3 said:
If this is so, why are there warnings to not open the cap when hot?
Was thinking the same thing...definitely has a pressure warning right on the cap.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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There SHOULD be pressure in the coolant reservoir with the engine at normal operating temperature: In these systems the reservoir is not solely an "expansion" or "coolant recovery" tank - it's an integral part of the pressurized system and provides the "air spring" against which coolant expansion and contraction works to control system pressure. Under normal conditions the hoses should be firm - not rock hard - firm. Normal reservoir level - cold - is about half full. NEVER check or adjust a modern cooling system coolant level when the engine is anywhere near operating temperature - cool or cold ONLY.

FWIW, in the changeover from top radiator tanks (downflow radiators) with pressure caps to our crossflow radiators with NO end tank caps/fills, there was a "coolant recovery" system used by about every car manufacturer: A radiator end or top tank pressure cap had a double internal seal and a flex hose piped from between the radiator and cap seals which led to a vented recovery tank hung on the firewall or inner fender. The main system was kept completely full and the recovery tank hose went to the bottom of the tank. As the engine heated and coolant expanded, coolant was bled off by the pressure cap seal system and sent to the recovery tank until the pressure cap setting stopped any more coolant from bleeding off. When the engine was shut down, as it cooled, contraction caused the coolant in the tank to be drawn back into the system, thus preventing any air from entering. The entire concept of keeping the cooling system air-free prevents corrosion and water pump cavitation which accelerates overheating.

I believe that KRSTS is referring to the obsolete coolant recovery system.
 

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STS
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Discussion Starter #10
So there still isn't any pressure on either of the rad hoses. The car will not overheat. I have drove the car through stop and go traffic, interstate, etc. It never overheats.

I assume this system is self bleeding? If not is there a bleeder valve somewhere? Or what would be the best way to bleed any air out of the system?

Im at a loss of what to do next. Any suggestions would be greatly appreciated.
 

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2006 STS4 V8 1SG & 2007 STS V8 1SE
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It certainly sounds like you still have a leak. If you're not losing coolent, it must be at a high-spot of the system. I'm not sure the best way to find the leak, so I'd be seeking a professional pressure test.

If you're using Dexcool, I'd recommend a flush & fill after it's fixed. Air exposure is not good.
 

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2005 STS Northstar RWD
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You may be able to pick up a simple pressure tester at an autoparts store. When i finished my flush and fill the upper hose had some pressure to it. I dont know that it was as firm as i have seen on other cars. What are your ambient temps? It may be running on the cooler side and not building up much pressure.
 

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Discussion Starter #13
The only thing that was leaking was the radiator and I installed a new one. I am not loosing coolant at all. Nothing else was damaged. I checked everything over 2 or 3 times. The damage was confined to a pretty small area.

The temps while I have been driving have been about 65-75 or so. So it has been cooler out then usual.

I'm thinking I have a lot of air in it or something. I am not sure but I think this system is supposed self bleed somehow. Does anyone know if that's correct?

Even if it did maybe I just have way too much air in there. I'm going to try to find some way to let some air out of it.

I just know I have absolutely 0 pressure on either hose. Top or bottom. It doesn't seem right to me at all.
 

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2005 STS Northstar RWD
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When the car is cool, remove the coolant res cap, and lightly squeeze the upper hose. Do it several times quickly to get some movement in the cooling res. You may be able to get rid of any trapped bubbles.

Also, have you pressure tested the res cap? Make sure it is holding pressure.
 

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2006 STS4 V8 1SG & 2007 STS V8 1SE
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This comes down to a pressure test. Get 'er done.

Does your car have transmission fluid lines running to the radiator you replaced?

Are you sure the replacement radiator is tight?
 

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This comes down to a pressure test. Get 'er done.

Does your car have transmission fluid lines running to the radiator you replaced?

Are you sure the replacement radiator is tight?
I wouldn't think transmission lines to the radiator would impact the coolant pressure. If it is a dual purpose radiator, for both engine coolant and transmission fluid, the fluid circuits would be separate so as the coolant and trans fluid don't mix.

But in generally, a Pressure test is definitely in order.
 

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Discussion Starter #18
Ok so I went and got a pressure testing kit.

Tested the expansion tank cap @ 15 PSI and it was good.

Put the other adapter on and tested the system via the expansion tank. 0 pressure. It wont hold anything. It just sounds like its not even screwed onto anything. It wont even temporarily go up to 1 PSI. Absolutly nothing.


What does this mean? I would think there would be a leak somewhere but I am not loosing any coolant. I park in a garage and I havent saw a single drop of coolant.


Any ideas?


Thanks again for all the help everyone.
 

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Discussion Starter #19
Ok so I drained all the coolant and refilled it slowly as per the instructions. I figured if there was a bunch of air in there somewhere maybe draining it and re filling it would get it out.

So I drained all of the coolant and when I went to refill it it only held about half of the coolant that I took out. So I started the engine got it up to temp then let it idle for a min. The level on the expansion tank barely went down and then the temp needle jumped a little bit above half so I shut it off. I waited a while but I guess not long enough and took the expansion tank cap off. When I did this a good bit of air came up through the expansion tank. like it was gonna come out at me but it didn't.

So since this air came out the level in the expansion tank dropped some and I put the rest of the coolant in it. Then I let it run and it runs fine. Not overheating. I ran it for about 15 mins just idling with the A/C on full blast and it wont overheat.

I called my mechanic who used to be my service tech at my local Cadillac dealer. He said as long as I am not loosing any coolant and its not overheating that it is fine and normal.


This just doesn't make sense to me. I understand the basics of an engine as I have built quite a few SBC's and LS engines from scratch. I know these are two different beasts but I just dont see how there shouldn't be any pressure on any of the hoses.


If I squeeze the bottom hose I can see the top hose flexing like they are both full of fluid. But like I said the coolant system doesnt hold any pressure at all. Of course when I was pressure testing it the engine was off and cool. So I dunno. Im at a loss.
 

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Although it's good you have no overheating, it is still important for a cooling system to be pressurized properly. In adverse conditions, the pressure prevents the coolent from boiling and then fail to transfer heat properly.

If you can't find & fix your leak, find someone who can. If not now, someday you will need a Cadillac dealer. Find the best in your area and build a good relationship. This might be a good time to start.
 
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