Need Options...coolant blowing out...
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Northstar Engines and System Technical Discussion Discussion, Need Options...coolant blowing out... in Cadillac Engine Technical Discussion; After going into the dealer with a coolant leak, on a '99 Deville with 102k on it, and spending $425. ...
  1. #1
    Quadrasteer is offline Cadillac Owners Fanatic
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    Need Options...coolant blowing out...

    After going into the dealer with a coolant leak, on a '99 Deville with 102k on it, and spending $425. for a water pump they're now telling me that pressure is building up in the cooling system and blowing out the overflow hose. What are my options?? Is there anything else it could be besides a head gasket? Right now my wife is driving it but I need to refill the res. daily.

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    ZSKI is offline Cadillac Owners Member
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    Re: Need Options...coolant blowing out...

    How much coolant are you adding at a time? Is it being overfilled? Coolant should level off at about two inches below the neck of the surge tank. Is the car overheating? Any codes? Is it emiting steam/smoke out of the exhaust? How does it run?

  4. #3
    1996deVille is offline Cadillac Owners Member
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    Re: Need Options...coolant blowing out...

    Quad,

    In the old days when this happened we'd check the thermostat. Now, this car is a bit different in that the cold side sees the stat opening, I believe... forum members correct me on this if I'm wrong!

    What temp are you seeing on your readout? Is it staying between 196 - 212? Or, does it move up to 226 and above, and stay there?

    This coolong system is complex - I'm still trying to "see" in my mind's eye, exactly what's happening with the return flow. If you look at your system, the overflow tank is pressurized, and the return is the small 1/4" line at the top of the tank. The upper radiator hose is the hose you see upon opening the hood - water is flowing to the radiator (again forum members, correct me if I'm wrong). The thermostat is in the housing where the lower radiator hose connects just below and forward of the upper hose.

    If you look over at the "overflow" tank, where you'd put the coolant, you'll see the 1/4" line connecting at the front of the tank - I believe this is also an air purge for the water pump (again forum members correct me if I'm wrong). Look down below the tank and you'll find the heater hoses connected to the sending tube that goes back into the block.

    If you had a head gasket problem you'd lose pressure in the system... the "pressure" in the system would flow out the exhaust.

    I went out a couple of days ago and did a few WOT's. The car temp hit 230 and since my house is fairly close to the offramp I parked the car at this relatively high temp. A few hours later I looked under the car to check for leaks. I had a fair amount of orange under the passenger side front wheel. I had just done the water pump a few days before and figured I messed up on tightening something - I double checked everything and all was tight.

    I suspect that when I parked the car at 230 degrees the engine temp increased with no coolant flow - the only place for this "super" heated fluid to go was out the 1/4" line to the overflow tank... it did, and the tank did its job and got rid of the "overeflow!"

    I let the car cool to normal temps and checked the level in the tank and I had lost some fluid - I refiled and have had no problems since...

    So - after all this babble - I'd check the thermostat and see if it is really doing its job.

  5. #4
    Quadrasteer is offline Cadillac Owners Fanatic
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    Re: Need Options...coolant blowing out...

    I see what you're saying. When I first got the ckeck coolant level message I may have overfilled the res. Then I not only had a slight water pump cover/gasket leak but the excess fluid blew out of the res. When I got the message again I definitely overfilled it because my wife had to take the car on a long ride. Now when I checked underneath the car it had antifreeze all over the bottom pass side and a little on the upper driver side (water pump). After they fixed the pump leak they may have not bleed the air out all the way and I found the res empty when we returned home. I probably overfilled it and have been over filling it ever since. I hope you're right. There are two things that might proove that theory wrong though. The fact that I have found the res empty more than once since the repair and the mechanic saying that we had an internal leak because when he pressure tested it the car ran rough due to the plug or plugs were getting wet with coolant. Personally I think that he only let the car run and used the message center to monitor the coolant temp (we found the message displayed when we picked the car up). Both times we were at the dealer they were rushed because they were busy and it was late in the afternoon. Mabye he pressure tested it again, mabye he didn't. I'm going to try not filling it and see what happens....Thanks

  6. #5
    1996deVille is offline Cadillac Owners Member
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    Re: Need Options...coolant blowing out...

    Quad,

    The "over" pressurization of the system stumps me... if there is a head gasket leak you should find wet plugs, unless it just isn't quite bad enough yet and the plugs burn out the little bit of coolant in the cylinder. If you do find a wet plug then you know you have a problem.

    When you pull off your cap (after the car cools awhile) does there seem to be a vacuum - like the cap still wants to stay on and is a little tough to pull off?

    My system didn't hold pressure well before I changed my water pump and hoses - now, it's great! So, check the hoses over real well if you've got a few years and some miles on the car.

    The coolant in the tank should be an inch or two below the cap - and stay there! I was losing some right before the water pump job, but in my case it was just evaporation from bad hose connections.

    Good luck hunting this problem down!

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    ZSKI is offline Cadillac Owners Member
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    Re: Need Options...coolant blowing out...

    Ranger, bbob, anyone...could use some help here! Quadrasteer, am I understanding you correctly...were you finding that the surge tank was being blown empty before the water pump change, I.E. were you seeing coolant on the bottom of the car (under the surge tank overflow tube) before the waterpump change? If you were leaking coolant via the waterpump and needed coolant out of the surge tank to replenish the system than you sould not have seen it running out of the overflow. However, if it was being blown out due to increased pressure than...out the overflow. How is the engine running temperature? Any smoke/steam out of the exhaust?

  8. #7
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    Re: Need Options...coolant blowing out...

    I think most of this can be explained by the system being a little low after the waterpump change and turning on the low coolant light. Then the surge tank has been overfilled and caused coolant to be pushed out the overflow hose when the engine is hot. It will keep doing this if it is overfilled.

    Check the surge tank when the engine has cooled off and the system is cold. The coolant level should be about 1.5 to 2 inches from the cap fitting. If it is higher than that then remove some coolant....if it is lower than that add some...otherwise, leave it alone. Drive the car for several days and see what happens. Don't add coolant unless the low coolant alarm comes on.

    The water pump doesn't pressurize the surge tank, per se. The coolant expansion and the vapor formation at hotter areas in the cylinder heads causes the system pressure to build and is controlled by the pressure cap. The water pump creates hydraulic pressure that causes flow thru the system...but you are forgettting the fact that the coolant bypasses the thermostat when it is closed thru the cast in bypass passage in the water crossover. The system works the same whether the stat is on the inlet or the exit (the Northstar is on the inlet)....the stat just meters flow to the radiator while the water pump is still pumping the same volume of coolant thru the engine thru the bypass passage that short circuits the radiator. That spring loaded "paddle" on the end of the thermostat is what controls the bypass flow in the Northstar with the inlet stat. The only real "flow" to the surge tank is thru the small, 3/8 line that is the vapor vent for the water pump that allows air to be purged from the system. The pressurized surge tank is deliberately a very quiet area for flow in the system so as to deareate the coolant. The larger 1 inch hose from the surge tank to the water pump inlet doesn't handle much flow at all.....it just provides an unrestricted positive pressure source to the water pump inlet to prevent cavitation.



    Head gaskets failing can manifest themselves in several ways. Plugs can get wet and cause misfire on startup. Cylinders can get full of coolant and hydrostatically lock on startup. Coolant can just disappear slowly with no sign of leaks. Coolant can be sucked into the combustion chamber while the engine is running. Pressure from combustion can blow back into the cooling system while the engine is running causing "false boiling" and blowing coolant back out of the overflow even though the engine is not overheating. The engine can overheat under load when combustion leakage causes aireation of the coolant causing lost cooling capacity...... etc. etc....

    There are lots of different ways that failing headgaskets can cause problems. There is no way that only ONE SPECIFIC RESULT can be predicted. I have seen all of the above and more characteristics and some combinations of the above...... so head gaskets cannot be blamed or exonorated based on symptoms...only by specific tests. The combustion chamber pressure test with shop air that I often recommend is the only reliable test that I know of...all others are still subject to conjecture and myth.

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    Re: Need Options...coolant blowing out...

    It sounds to me like the operation of the surge tank resembles that of the old pressure systems before the catch can. You just left some room in the top tank of the radiator for expansion when you filled the system. Unless the system overheated nothing came out the overflow and system pressure was comtrolled by the cap. No air entered the system at cool down unless the system pressure dropped below ambient when the system was originally filled. Then the vacuum vent would equalize the pressure. Everything old is new again.

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    Re: Need Options...coolant blowing out...

    How do you guys get a cooling system temp readout on your info systems?????

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    Re: Need Options...coolant blowing out...

    Quote Originally Posted by dkozloski
    It sounds to me like the operation of the surge tank resembles that of the old pressure systems before the catch can. You just left some room in the top tank of the radiator for expansion when you filled the system. Unless the system overheated nothing came out the overflow and system pressure was comtrolled by the cap. No air entered the system at cool down unless the system pressure dropped below ambient when the system was originally filled. Then the vacuum vent would equalize the pressure. Everything old is new again.

    Well...sort of, yea. The remote pressurizes surge tank does allow for the deareation of the coolant as coolant flowing thru the radiator does not have time to deareate much due to the flow and turbulence. Also, it is difficult to have a real time coolant level sensor in the radiator that is effective due to the flow activity in the radiator, air bubbles and such that can fool a sensor and the fact that the sensor would have to be low in the radiator....so that it would be below the level of the heads on the engine. The pressurized surge tank is the high point of the system and it has little flow and the coolant is quiet and deareated so it is an excellent place for an accurate low coolant level sensor that can operate accurately all the time the engine is running and allow a warning of low coolant before any of the engine components run dry. It is a better way to go.

    Also, with the high flow systems and high flow water pumps with inlet stats there is a pressing need for a positive pressure source directly at the water pump inlet to pressurize the water pump inlet to prevent cavitation. The pressure cap on the rad will not do this as it is divorced from the water pump inlet and there are several sources of pressure drop before the system pressure sees the water pump inlet. The pressurized surge tank allows routing max system pressure directly to the water pump inlet.... It is a better way to do it.

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    Re: Need Options...coolant blowing out...

    All good points and obviously well thought out. It appears though that the catch can type systems have the potential of exposing the coolant to more ambient air than the old radiator systems because they dump and fill the vented catch can with every heatup and cooldown cycle.

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    zonie77 is offline Cadillac Owners Connoisseur
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    Re: Need Options...coolant blowing out...

    Have you put in a new thermostat? I didn't notice that in your posts (I might have missed it). Only use a GM thermostat.

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    Quadrasteer is offline Cadillac Owners Fanatic
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    Re: Need Options...coolant blowing out...

    A few answers and a few questioms.....First, they did change the thermostat when the water pump job was done along with a new cover. The car never overheats and has only gone up to 221deg. on a recent warm day. It usually hovers around 209. The engine dosen't skip a beat and there is no water or steam in the exhaust. It was wet on the bottom under the surge tank before the pump change but I did overfill it. They didn't do a good job of getting the old coolant out so it looks brown and the tech put only one tube of Bars Leak in. He put half a tube in the upper hose and the other half in the res. This is after discussing draining the system from the lower hose and adding the sealer back into it. This dealership does not believe in using the sealer and said that it clogs up heater cores! Now the questions... If the surge tank has a 1" hose going to the pump and a 3/8" vapor vent for the pump, which is the overflow hose? Is it still not reccomended to flush the coolant system? Would you reccomend tightening the head bolts to spec? Has anyone used the head gasket sealer from Bars with any luck? Thanks. I'll check the coolant level tomorrow when my wife gets back, it's been two days since i refilled it.

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    BeelzeBob's Avatar
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    Re: Need Options...coolant blowing out...

    Quote Originally Posted by Quadrasteer
    A few answers and a few questioms.....First, they did change the thermostat when the water pump job was done along with a new cover. The car never overheats and has only gone up to 221deg. on a recent warm day. It usually hovers around 209. The engine dosen't skip a beat and there is no water or steam in the exhaust. It was wet on the bottom under the surge tank before the pump change but I did overfill it. They didn't do a good job of getting the old coolant out so it looks brown and the tech put only one tube of Bars Leak in. He put half a tube in the upper hose and the other half in the res. This is after discussing draining the system from the lower hose and adding the sealer back into it. This dealership does not believe in using the sealer and said that it clogs up heater cores! Now the questions... If the surge tank has a 1" hose going to the pump and a 3/8" vapor vent for the pump, which is the overflow hose? Is it still not reccomended to flush the coolant system? Would you reccomend tightening the head bolts to spec? Has anyone used the head gasket sealer from Bars with any luck? Thanks. I'll check the coolant level tomorrow when my wife gets back, it's been two days since i refilled it.

    Neither of the hoses you mention is the overflow hose.

    The overflow hose is the hose just under the pressure cap......possibly there is just a fitting or nipple there at the moment....the fitting just under the cap is the overflow port for the surge tank.

    Make sure that the pressure cap is sealing and that it is the correct cap for the application.

    Trying to "retighten" the head bolts is not recommended. The bolts were installed with a locktite thread locker. Any tightening torque would have to overcome the existing thread locker and would be very inaccurate. The only way to really try to do this accurately would be to loosen each bolt and then retension it to the correct torque and angle from scratch. I wouldn't do this unless you are fixing to pull the heads.

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    1996deVille is offline Cadillac Owners Member
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    Re: Need Options...coolant blowing out...

    The overflow hose is the small one right next to the cap... just lift it and you'll see that it doesn't connect to anything, it is just an overflow drain tube.

    You know, everyone I've talked with will share bad experiences with Bars Leak. It will find its way to low places and stay there - I have a feeling that even if a person could get to the petcock on the radiator nothing would flow b/c the Bars Leak would settle and close it off... the coolant SHOULD have enough sealing properties if replaced every two years. The Bars Leak demand upon flushing the system does seem very strange.

    They should not have put any in the overflow tank - you'll have to take it off and clean it out, what a drag...

    How long will the level stay consistent in the overflow tank?

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