lovemysts Posted December 13, 2011 Report Share Posted December 13, 2011 I have a 1996 Seville STS. This year I have replaced the water pump, thermostat, radiator, heater core, and all connecting hoses. As I fix one issue, a new one develops. The whole system has pretty much been replaced. Now I have a coolant leak at the rear of the motor, passenger side, near where the hoses go to the heater core. Runs fine then 10 minutes after you shut off the engine it starts leaking out with a quick drip from this area. Any ideas on what it could be now??!!! Link to comment Share on other sites More sharing options...
Cadillac Jim Posted December 13, 2011 Report Share Posted December 13, 2011 I would check the overflow hose from the base of the radiator cap. If there is bubbling in the engine after shutoff, it may cause a temporary overflow condition. This will happen if your coolant is less than 50-50 antifreeze. -- Click Here for CaddyInfo page on "How To" Read Your OBD Codes-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data -- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC Yes, I was Jims_97_ETC before I changed cars. Link to comment Share on other sites More sharing options...
KHE Posted December 13, 2011 Report Share Posted December 13, 2011 Wheck the coolant bypass pipes that run across the back of the engine. They might be starting to rust through and causing a coolant leak. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
lovemysts Posted December 13, 2011 Author Report Share Posted December 13, 2011 I would check the overflow hose from the base of the radiator cap. If there is bubbling in the engine after shutoff, it may cause a temporary overflow condition. This will happen if your coolant is less than 50-50 antifreeze. I keep 50/50 mix, no bubbling, and it's not coming from the overflow. This is why I'm so stumped!!! A mechanic, just in conversation not seeing the car, said it may be the manifold intake gasket. The leak is in that general area, but is that even possible to have coolant leaking there? Why would there be coolant there??!!! Engine runs perfect. Wouldn't a gasket like that affect overall performance? I just feel that I'm overlooking something within the cooling system that still needs to be replaced. Any and all ideas are welcome! Thank you for all input!!! Link to comment Share on other sites More sharing options...
lovemysts Posted December 13, 2011 Author Report Share Posted December 13, 2011 Wheck the coolant bypass pipes that run across the back of the engine. They might be starting to rust through and causing a coolant leak. Now this is something I haven't thought of! I'm going to check it out today. This could be a possibility. In May I had to replace rusted brake lines. Some places such as this are starting to show signs of rust now (car was in Iowa for first 10 years and in Florida since). Thanks for the suggestion!! I'll post back with what I find. Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 13, 2011 Report Share Posted December 13, 2011 On this engine the INTAKE MANIFOLD GASKET or SEALS have NOTHING to do with coolant, NOTHING..... That mechanic is wrong 100% As KHE said, if you have done all that work, the two heater pipes that wrap around the back can be rusted through Here is a photo of their location and heater hoses Here is a photo of my rusted heater pipes on my 96 Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
lovemysts Posted December 13, 2011 Author Report Share Posted December 13, 2011 On this engine the INTAKE MANIFOLD GASKET or SEALS have NOTHING to do with coolant, NOTHING..... That mechanic is wrong 100% As KHE said, if you have done all that work, the two heater pipes that wrap around the back can be rusted through Here is a photo of their location and heater hoses Here is a photo of my rusted heater pipes on my 96 Thank you so much for this diagram!! I've spent the last hour trying to find one so I would know what I'm looking for!! Also thank you for confirming the mechanic was wrong. That just didn't make any sense to me. Any advice on replacing these lines? Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 13, 2011 Report Share Posted December 13, 2011 By the way, SOME intake manifolds CAN leak coolant as coolant runs through them, but NOT on the Northstar. Its not a function of the mechanic being dead wrong, its a function of him being wrong regarding this engine, the Northstar, if he knew the engine, he would not make that statement. Those pipes are hard to replace, it will not be a picnic. You will need to tilt the engine forward as much as possible by removing the dogbones and maybe loosening the rear engine mount to tilt the engine forward. If you had this tool, it would make the job easier http://www.etoolcart.com/engine-tilter-thx419x.aspx Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
mike5514 Posted December 13, 2011 Report Share Posted December 13, 2011 Guessing at a coolant leak is iffy at best rent a pressure tester from autozone (deposit only) take a strong light and mirror and look for leaks. Start at surge tank work to fire wall over to other side back to front and radiator.Mike Link to comment Share on other sites More sharing options...
BodybyFisher Posted December 13, 2011 Report Share Posted December 13, 2011 That is true mike, parts replacing can be expensive. Where the leak is coming from SHOULD be confirmed before just replacing parts. As we know the COOLANT TANK can leak under pressure, clamps can be loose, etc. Putting the car up on a lift and inspecting the heater pipes is easy. Pressure testing is the best diagnostic tool Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
lovemysts Posted December 14, 2011 Author Report Share Posted December 14, 2011 By the way, SOME intake manifolds CAN leak coolant as coolant runs through them, but NOT on the Northstar. Its not a function of the mechanic being dead wrong, its a function of him being wrong regarding this engine, the Northstar, if he knew the engine, he would not make that statement. Those pipes are hard to replace, it will not be a picnic. You will need to tilt the engine forward as much as possible by removing the dogbones and maybe loosening the rear engine mount to tilt the engine forward. If you had this tool, it would make the job easier http://www.etoolcart.com/engine-tilter-thx419x.aspx You are absolutely right. This guy is a great mechanic just has no experience with northstar and told me so. Thanks for all the info! This is exactly what I needed! Link to comment Share on other sites More sharing options...
lovemysts Posted December 14, 2011 Author Report Share Posted December 14, 2011 This year started with the radiator being replaced(cracked plastic tank on the side of radiator). All of the cooling system was still original so the new radiator has stressed the rest of the old worn parts, and one by one they have had to be replaced. Those heater lines are just about the only thing left. Didn't know autozone rented the pressure tester. Good to know! So I guess in the a.m. it's off to autozone then a thorough inspection to find the culprit! Will definately post what I find. Just one more question for now - my driveway is not flat, maybe a 35 degree slant. Will that affect the pressure test? Thank you all again for all the info! It is much appreciated! I was stumped and you have given me some new things to look for! Link to comment Share on other sites More sharing options...
lothos Posted December 14, 2011 Report Share Posted December 14, 2011 Just one more question for now - my driveway is not flat, maybe a 35 degree slant. Will that affect the pressure test? I don't believe it would. The pressure in the coolant system should be the same whether the car is level or not. WARNING: I'm a total car newbie, don't be surprised if I ask a stupid question! Just trying to learn. Cheers! 5% discount code at RockAuto.com - click here for your discount! Link to comment Share on other sites More sharing options...
rockfangd Posted December 14, 2011 Report Share Posted December 14, 2011 please read my topic let thhe bad news fly. on page 1 and it will show the pipes and hoses, prices and everything you would need to do the job for parts GM FAN FOREVER Nice, clean, luxury= fine automobile Link to comment Share on other sites More sharing options...
lovemysts Posted December 14, 2011 Author Report Share Posted December 14, 2011 please read my topic let thhe bad news fly. on page 1 and it will show the pipes and hoses, prices and everything you would need to do the job for parts Thank you for leading me to your topic! I appreciate the diagram and part numbers! How's the work going on yours? Link to comment Share on other sites More sharing options...
Ranger Posted December 15, 2011 Report Share Posted December 15, 2011 Didn't know autozone rented the pressure tester. Autozone does not "rent" tools. They loan them out for free (hoping you'll buy your parts from them). They actually charge you for the tool and then refund the money when it is returned. Link to comment Share on other sites More sharing options...
rockfangd Posted December 15, 2011 Report Share Posted December 15, 2011 lol. I bought all the parts and it ended up being the heatercore cracked where one of the hoses attached. I decided not to install the pipes because the heatercore solved the problem. I have done these pipes before and honestly the worst part is the 2 7mm bolts that clamp the pipes to the back of the engine. I find many of thm start leaking at the T toward the passenger side GM FAN FOREVER Nice, clean, luxury= fine automobile Link to comment Share on other sites More sharing options...
lovemysts Posted July 23, 2012 Author Report Share Posted July 23, 2012 Ok! 8 months later! Thanks to everyones suggestions and diagrams I was able to find the problem! It was the coolant lines behind the motor. While I was at it I replaced every last line! Now ALL of the whole cooling system has been replaced............. And I still have a leak!!! It just seems like the coolant isn't flowing through the whole system. You can check the coolant, know it's full, drive 5 miles and the car overheats and small amouts of coolant then comes out from several places. Twice of that and I haven't driven it anymore! Now, just sitting in the driveway (haven't driven it in a month just start it up let it run a few minutes every few days) it will just randomly leak coolant from the driver's side even if it hasn't been started in a day or two! Does anyone have any clue what it could be now? I would truly appreciate some advice. Should I just cut my losses and let it go or is this easily fixed? Thank you in advance for your replies. Link to comment Share on other sites More sharing options...
KHE Posted July 23, 2012 Report Share Posted July 23, 2012 Ok! 8 months later! Thanks to everyones suggestions and diagrams I was able to find the problem! It was the coolant lines behind the motor. While I was at it I replaced every last line! Now ALL of the whole cooling system has been replaced............. And I still have a leak!!! It just seems like the coolant isn't flowing through the whole system. You can check the coolant, know it's full, drive 5 miles and the car overheats and small amouts of coolant then comes out from several places. Twice of that and I haven't driven it anymore! Now, just sitting in the driveway (haven't driven it in a month just start it up let it run a few minutes every few days) it will just randomly leak coolant from the driver's side even if it hasn't been started in a day or two! Does anyone have any clue what it could be now? I would truly appreciate some advice. Should I just cut my losses and let it go or is this easily fixed? Thank you in advance for your replies. Test the coolant for exhaust gasses. Autozone has the tester in their Loan-a-Tool program and you will need to buy the test fluid. Make sure not to add coolant prior to the test as it will affect the test results. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
lovemysts Posted July 23, 2012 Author Report Share Posted July 23, 2012 Ok will do. What does it mean if there are exhaust gases? Nevermind ....... I just read about........ I really hope that's not it. :/ Link to comment Share on other sites More sharing options...
joeb Posted July 24, 2012 Report Share Posted July 24, 2012 what places does the coolant leak from? you say there are several? you replaced entire piping system so you know all the parts well. if coolant leaks from a clamped connection and hose and clamp and nipple are new, what does that tell you? my upper radiator hose blew off 4 yrs ago. i knew that was a sign of high pressure in system. i ended up doing a hg repair but that is not to say yours is due. if your car leaks coolant everytime you drive, than its hard to acurately gauge coolant loss into motor if you have external leak. we could say monitor coolant use to dial in headgasket issues but you keeping leaking it externally. Link to comment Share on other sites More sharing options...
lovemysts Posted July 25, 2012 Author Report Share Posted July 25, 2012 The coolant doesn't always leak from the same place. It appears to come from the connections (which I have made sure are all secure). It's seems so random. For example, I can drive it three miles, get home and an hour later it will leak from the T connection. Then two days later without even being started it will leak from the bottom radiator hose. I am losing way more coolant than what is visible. I'll fill the coolant, idle the car for a few minutes, see the small leaks, then the next time I start it there's no coolant in it at all. When driving or just sitting at an idle it starts overheating in about 5 minutes. All of my problems also started with a blown upper radiator hose. I replaced the raditor and its hoses then. Systematically each component failed and I replaced over the last two years. The system is obviously under high pressure, but I didn't know that was a sign of damaged head gaskets. Link to comment Share on other sites More sharing options...
lovemysts Posted July 25, 2012 Author Report Share Posted July 25, 2012 I discovered a new problem yesterday. My trunk, backseat, and back floor boards are soaking wet! The front seats are dry and the front floor boars are only damp. It hasn't rained so I know it's not from a window. This is quite a lot of water! I dried as much of it as I possibly could and let the rest air dry. Last night it was pretty dry considering how soaking wet it had been. This morning it's full of water again! Does anyone have any idea what's causing this? Link to comment Share on other sites More sharing options...
KHE Posted July 25, 2012 Report Share Posted July 25, 2012 I discovered a new problem yesterday. My trunk, backseat, and back floor boards are soaking wet! The front seats are dry and the front floor boars are only damp. It hasn't rained so I know it's not from a window. This is quite a lot of water! I dried as much of it as I possibly could and let the rest air dry. Last night it was pretty dry considering how soaking wet it had been. This morning it's full of water again! Does anyone have any idea what's causing this? If it is not coolant, then I would suspect the evaporator condensate drain is plugged and the condensate from the air conditioning is backing up and flooding the carpet. The evaporator drain is on the passenger side of the engine compartment at the bottom of the HVAC box. Use a small screwdriver to gently unclog the drain. Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Texas Jim Posted July 25, 2012 Report Share Posted July 25, 2012 I discovered a new problem yesterday. My trunk, backseat, and back floor boards are soaking wet! The front seats are dry and the front floor boars are only damp. It hasn't rained so I know it's not from a window. This is quite a lot of water! I dried as much of it as I possibly could and let the rest air dry. Last night it was pretty dry considering how soaking wet it had been. This morning it's full of water again! Does anyone have any idea what's causing this? Since you are losing so much coolant... it could be a heater core leaking. If your driveway slopes quite a bit, it could be running UNDER the front carpet and pooling in the back floorboard... Just a guess.... Link to comment Share on other sites More sharing options...
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