coolant leak in 94 sedan deville (4.9)
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HT4100 4.1, 4.5, 4.9 Discussion, coolant leak in 94 sedan deville (4.9) in Cadillac Engine Technical Discussion; I just bought this car with 78,000k on it, and after letting it sit in the driveway for a couple ...
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    timko is offline Cadillac Owners Member
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    coolant leak in 94 sedan deville (4.9)

    I just bought this car with 78,000k on it, and after letting it sit in the driveway for a couple weeks (it is my first car and I just got my license), the coolant has started to leak under the hood on the passanger side of the car. It appeared to be mostly wet around the radiator cap so I replaced it. It continued to leak and I can't find the location. We changed the thermostat with no results again. I get messages periodicly that the engine is hot after driving about 10 miles. My father thinks there may be an air pocket somewhere. Any thoughts or suggestions?

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    Re: coolant leak in 94 sedan deville (4.9)

    is your passenger side floor wet at all?

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    timko is offline Cadillac Owners Member
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    Re: coolant leak in 94 sedan deville (4.9)

    Nothing is wet inside the car, just under the hood. Another problem I have is the engine running rough at startup and at low speeds. It goes away after a little bit. My father beleives one of the cylanders isnt burning right. Thanks ahead of time for any help I may receive :coolgleam

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    Re: coolant leak in 94 sedan deville (4.9)

    Quote Originally Posted by timko
    I just bought this car with 78,000k on it, and after letting it sit in the driveway for a couple weeks (it is my first car and I just got my license), the coolant has started to leak under the hood on the passanger side of the car. It appeared to be mostly wet around the radiator cap so I replaced it. It continued to leak and I can't find the location. We changed the thermostat with no results again. I get messages periodicly that the engine is hot after driving about 10 miles. My father thinks there may be an air pocket somewhere. Any thoughts or suggestions?

    What you describe may be coolant loss due to overheating or a leak somewhere.....

    If you are gettting the hot light on then the engine is getting overheated for some reason. If there is a leak then the coolant may be getting so low that it overheats.

    Air pockets are not a problem with that engine.

    The cooling system on that car does require constant maintenance due to the fact that it has an aluminum engine block. The coolant is the conventional green, silicated coolant and needed to be replaced every 2-3 years/24-32,000 miles to keep the corrosion inhibitors in the coolant up to full strength to prevent internal engine damage due to corrosion.

    I would suggest doing several things. Go to a tool rental or auto parts store and rent a cooling system pressure checker. It is a small hand pump that hooks to the radiator cap fitting. Pump up the system to its normal operating pressure of 15 PSI when the engine is cold. This way any leak that is happeneing when the engine is hot and the system is pressurized will be evident even with it cold. Pump it up and look for leaks.

    Double check that you have the correct radiator cap for your system... Not all rad caps are the same. Yours should have the normal spring loaded seal to the bottom of the rad fitting, a seal around the perimeter of the cap AND a little "drop valve" in the very center of the spring loaded part of the cap that allows coolant to be sucked back from the coolant recovery bottle when the system cools to keep the radiator full.

    Get a coolant checker (inexpensive ones are availabe at any auto parts or discount store) and check the concentration of your coolant. It should test good for freeze protection to -40. If the coolant is weak it could cause premature boiling (the coolant guards against freezing and boiling) and false overheating symptoms and/or coolant loss.

    Drain the cooling system/radiator and refill with FRESH 50/50 coolant/distilled water premixed. When refilling the system, add 6 of the GM coolant supplement pellets/2 tubes of the commonly available BarsLeaks "golden seal" powder to make sure the cooling system is sealed internally to the engine. The sealant is absolutely mandatory for your engine to guard against internal coolant leakage. It was factory installed but needs to be replenished occasionally. Even if the coolant concentration checks "good" the coolant needs to be frequently replaced.

    Fill the sytem at the radiator cap fitting to the very top. Install the cap. Fill the coolant recovery bottle. Drive the car for several short trips and allow it to cool inbetween to eliminate any air and for the coolant level to stabilize. Double check when COLD that the radiator is staying completely full. If the coolant level drops in the radiator and the coolant recovery bottle stays full then the rad cap is not correct or is not operating correctly.

    If this is your first car and you want to learn about it and how it works and how to fix it order the factory service manual from Helms or look for one on ebay. It is invaluable in explaining how all the sytems work and how to trouble shoot and repair them. Get the Helms manual only. Chiltons and Haynes and such are pretty useless.

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    timko is offline Cadillac Owners Member
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    Re: coolant leak in 94 sedan deville (4.9)

    I found out that the coolant is prematurely boiling and it seems it is coming out of the resevoir. My dad things that it might be the pump that is causing this. Any ideas or suggestions?

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    Re: coolant leak in 94 sedan deville (4.9)

    Quote Originally Posted by timko
    I found out that the coolant is prematurely boiling and it seems it is coming out of the resevoir. My dad things that it might be the pump that is causing this. Any ideas or suggestions?

    Uhhh....water pumps do not generally cause overheating. Waterpumps will leak and the bearings will fail and make noise and such...but...as long as that pulley on the water pump is being turned by the serpentine accessory drive belt the pump impeller inside will be turning and pumping the coolant and the system should not overheat. There are rare cases of the impeller falling off the water pump shaft on some of the cheaper aftermarket water pumps....rare but it could happen...that is why you want an OEM water pump from Cadillac if you do need one. Personally, I would seriously doubt that it is the pump. You can confirm this by taking the 1 inch hose off at the thermostat housing fitting and starting the engine briefly. Do this with the engine cold. When you start the engine if coolant pours out of the fitting at the thermostat housing then the water pump is pumping and it is NOT the problem.

    Ideas and suggestions...???....did you try the things listed in the post above to diagnose the problem????

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    timko is offline Cadillac Owners Member
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    Re: coolant leak in 94 sedan deville (4.9)

    I changed the radiator cap again to a 15psi one today and took it out for it's longest trip yet. I climbed lots of hills and sat in traffic giving it plenty of opportunity to heat up and there was no leaks, and no "engine coolant hot" message as i was experiencing before just takin it a couple miles down the road. I dont understand it? I hope it continues to run fine.

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    JoeBleed is offline Cadillac Owners Member
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    Re: coolant leak in 94 sedan deville (4.9)

    It is likly that either the cap that you had on it before was a lower presure cap or more likly it wasn't the right cap as in it didn't fit corectly. This allowed the coolent to leak out when it biiled instead of going into the overflow tank. the reason the watter probalby boild is because there was no presure builing up on the system and/or the coolant isn't mixed well. (proper ratio).

    keep an eye on the water level and the temp gage/overheat light which ever.
    as mentioned before it is very important that you use the GM tablets. any GM dealer should have these instock in their parts dept. as for the BarsLeaks that was also sugest.. me personly wouldn't, and don't in mine, use anything other than the GM pelets. 225,000 + miles on it and working good. and no not same fluid. i change it regulery and flush the system and add new pelets every time. the pelets are prety cheap around here so price shouldn't be a concern. if they are over 6 bucks a pack look else were. i don't rember exactly what i paid last time but i usualy by 2 packs for around 6 bucks.

    good luck.

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    Re: coolant leak in 94 sedan deville (4.9)

    Quote Originally Posted by timko
    I changed the radiator cap again to a 15psi one today and took it out for it's longest trip yet. I climbed lots of hills and sat in traffic giving it plenty of opportunity to heat up and there was no leaks, and no "engine coolant hot" message as i was experiencing before just takin it a couple miles down the road. I dont understand it? I hope it continues to run fine.

    Maybe it was a bad cap. If the cap was not pressurizing the system then the coolant could easily boil "prematurely". Realize that water boils at 212 in a pot on the stove. That is the normal operating temp of the engine. The addition of the 15 PSI pressure cap raises the boiling point of the water up to about 225 or so....check your physics textbook for the exact boiling point of water at 15 PSI. The addition of the green "coolant" raises the boiling point of the system even higher...much much higher. With a 15 PSI cap AND the 50/50 coolant/water mix the system will not boil until 265 degrees.... Quite a difference from the 212 that water boils at.

    So...it could have been the cap....it still could be a weak anti-freeze mixture. Just because it is not overheating anymore doesn't mean you are done. You still need to check the coolant concentration and service the coolant system with fresh coolant and the coolant sealer/supplement.

    The main way to avoid breakdowns and problems with your car in the future is to maintain it today.....seems like more work but it beats sitting on the side of the road at 2:00 AM with a broken car.....

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    timko is offline Cadillac Owners Member
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    Re: coolant leak in 94 sedan deville (4.9)

    Christ this episode is not over . Thanks for all your information, especially bbob. I'll list all my symptoms right here maybe someone has had a similar problem. The reservoir gets filled up for some reason with coolant and overflows and i see bubbles coming up. I get "engine coolant hot" and sometimes "engine hot" messages on the dashboard. Another thing i didnt mention is that now my heat doesn't work. The water pump is making strange noises. Once i heard i gurgling after a turned my car off and looked under the hood but maybe thats normal? Also, probably not related, but the engine runs a little rough and has this funny sort of screeching when i start it that continues for some time after driving but it goes away with about 5-10 minutes. You guys are awesome.

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    Re: coolant leak in 94 sedan deville (4.9)

    Quote Originally Posted by timko
    Christ this episode is not over . Thanks for all your information, especially bbob. I'll list all my symptoms right here maybe someone has had a similar problem. The reservoir gets filled up for some reason with coolant and overflows and i see bubbles coming up. I get "engine coolant hot" and sometimes "engine hot" messages on the dashboard. Another thing i didnt mention is that now my heat doesn't work. The water pump is making strange noises. Once i heard i gurgling after a turned my car off and looked under the hood but maybe thats normal? Also, probably not related, but the engine runs a little rough and has this funny sort of screeching when i start it that continues for some time after driving but it goes away with about 5-10 minutes. You guys are awesome.

    Your symtoms just indicate that the coolant in the system is boiling prematurely. DID YOU CHECK THE COOLANT CONCENTRATION YET ???? or any of the other things mentioned above.

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    Re: coolant leak in 94 sedan deville (4.9)

    [QUOTE=timko]The reservoir gets filled up for some reason with coolant and overflows and i see bubbles coming up. I get "engine coolant hot" and sometimes "engine hot" messages on the dashboard. Another thing i didnt mention is that now my heat doesn't work.


    It sounds like you're up against either a bad head gasket or (worse still) a cracked head or liner. I had an older 4.1 that had the same symptoms when the head gasket went. The compression gases start to displace the water in the cooling jacket and drive the coolant into the bottle. The higher lines (like the heater lines) become air-locked. There can be so much air in the system due to the gases that you actually see bubbles in the radiator or in the overflow bottle. A way you can find out for sure is a hydrocarbon test of your cooling system. A local garage can do it or you can get the kit from Matco or (I beleieve) Snap-On. Basically, you monitor the gases coming out of the radiator for a few minutes by passing it through an indicator liquid. If the liquid changes color, hydrocarbons are present in the cooling system and they're probably coming from the head gasket.

    Hope this helps.

    dac675

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