Question : Several coolant system issues

[skywalker]

OK, I'm having several very strange coolant issues. First off, it's an 01 Monte Carlo, 3400 block...the LIM is leaking, and the motor has over 140k miles on it, so I'm most likely not going to be replacing it. The temp sensor went out at about 120k miles, and I replaced it, and it worked fine up until about 135k, when it failed again...I replaced it again, and it stayed broken. Here's the weird thing. You reset the ECU by pulling the lead on the battery...and when you hook it back up the temp sensor works fine until about 25 minutes into your first trip, after it's warmed fully up to temp, the readout on the sensor suddenly starts slowly and steadily dropping, then when it gets down to about 1/4 of the way up the gauge it just drops like you flipped a switch, and the ECU turns on the fans permanently as the failsafe and the temp gauge never budges at all no matter how many times you restart the car and such until you reset the ECU again, at which point it starts working again, and repeats the pattern.

Then today the low coolant light came on, and the system was about a quart low in the radiator...topped it off, but the low coolant light didn't go away. So...I mean it sounds like the coolant level sender is whacked...but with the temp sensor all messed up too, there's literally NO way to know what's going on in there...any ideas? Anyone ever seen a temp sensor gauge do anything like that before?

[60dgrzbelow0]

Your excellent description of symptoms can only be caused by a few things and all of them need immediate attention. (1) If you have filled the radiator and still get these odd spikes in temperature...it is possible that you have some trapped air either in the upper block jackets or adjacent the water pump and heater lines hosing. Find the bleeder valves and run the engine long enough to have the thermostat open up. With bleeder valves cracked...put a towel around it to absorb any escaping coolant and watch for the hissing of air as it is forced out of the system. When nothing but hot coolant is pouring out, close the bleeder valves and when the engine is cold...top off the radiator. (2) Your thermostat could have gone bad. Replace it with the one having the recommended baseline opening temperature, Sometimes people change out their thermostats for one having the wrong temperature settings. In some cases...thermostats can be installed UPSIDE DOWN. If that has happened, it will not work. (3) Your water temp sensors will not send the right signals to the ECM if there is nothing but air/ steam inside the spaces near them and require direct contact with hot coolant to get the proper signals going. (4) If you observe white steam from your tail pipe, then your IM has been compromised and coolant is migrating into the engine cylinders and is being burned and exhausted. This is bad for the engine innards and needs immediate repair. If your engine oil looks like a chocolate milkshake, then your LIM has been compromised and coolant has invaded your oil supply. The chemicals and acids created by the presence of anti-freeze in your engine oil will destroy the Babbitt surfaces on all your engine bearings. The cam shaft can seize and snap in half at the offending journals. This is a biggy in the way of lunching the motor. (5) Having dissimilar cooling in the engine because of trapped air pockets can cause odd hot spots in various cylinders and damage pistons and rings.

These are most of the problems related either the absence of coolant in a running engine,.,....or what happens when coolant goes where it is not intended to be. Hope these ideas help.

[skywalker]

Your excellent description of symptoms can only be caused by a few things and all of them need immediate attention. (1) If you have filled the radiator and still get these odd spikes in temperature...it is possible that you have some trapped air either in the upper block jackets or adjacent the water pump and heater lines hosing. Find the bleeder valves and run the engine long enough to have the thermostat open up. With bleeder valves cracked...put a towel around it to absorb any escaping coolant and watch for the hissing of air as it is forced out of the system. When nothing but hot coolant is pouring out, close the bleeder valves and when the engine is cold...top off the radiator. (2) Your thermostat could have gone bad. Replace it with the one having the recommended baseline opening temperature, Sometimes people change out their thermostats for one having the wrong temperature settings. In some cases...thermostats can be install UPSIDE DOWN. If that has happened, it will not work. (3) Your water temp sensors will not send the right signals to the ECM if there is nothing but air/ steam inside the spaces near them and require direct contact with hot coolant to get the proper signals going. (4) If you observe white steam from your tail pipe, then your UIM has been compromised and coolant is migrating into the engine cylinders and is being burned and exhausted. This is bad for the engine innards and needs immediate repair. If your engine oil looks like a chocolate milkshake, then your LIM has been compromised and coolant has invaded your oil supply. The chemicals and acids created by the presence of anti-freeze in your engine oil will destroy the Babbitt surfaces on all your engine bearings. The cam shaft can seize and snap in half at the offending journals. This is a biggy in the way of lunching the motor. (5) Having dissimilar cooling in the engine because of trapped air pockets can cause odd hot spots in various cylinders and damage pistons and rings.

These are most of the problems related either the absence of coolant in a running engine,.,....or what happens when coolant goes where it is not intended to be. Hope these ideas help.

First off, I appreciate the response.

I guess here's my main question, because I'm either having a hard time understanding or a hard time expressing my issue...when the PCM goes into failsafe and disables the AC clutch and turns the fan relay on permanently, does it also completely disable the temperature readout on the gauge? Because you reset the ECU, and the temp gauge works normally...then at some point the gauge starts dropping and the system goes into fail safe, then from that point up until you reset the ECU, no matter how long of a time span you go, the temp gauge doesn't budge. And I don't mean it just reads low, or doesn't quite make it to the first line. I mean it literally doesn't budge. I've put a piece of tape on the dash to mark the spot where it starts out at and have driven for hours and it doesn't move a smidge. But I could pull over and reset the ECU, and hop right back into the car and turn it back on, and the gauge would instantly start reading again, up until about 20 minutes later or so when it drops down and goes back into failsafe. Does this still match the symptoms? It's not really 'spiking'...it goes up to normal temp (right at the half way point, sometimes a needlewidth over, sometimes a needlewidth under), then starts dropping slowly and steadily during the trip, then just flicks off like you flipped a switch, and doesn't budge again ever until the ECU is reset.

BTW, the LIM is leaking on the car, and has been for a while, but it's only leaking coolant out the sides, and either a very small amount of oil is getting into the coolant (floats to the top and ends up in the overflow bottle, but it's really not very much) or I have a hairline crack in the radiator core that's allowing some transmission fluid into the coolant system, but so far no coolant is going into the oil pan and it's not burning coolant either. I'm familiar with the coolant-in-the-oilpan issue...a week ago I had to trash my fiancee's old 3100 block Buick and buy a new car when her car overheated and warped the block and dumped 5 or 6 quarts of coolant into the oil pan. I've had a really bad month with the 60degreev6. lol

[60dgrzbelow0]

Since your car is OBD II, it might be very helpful to stop by Autozone and ask them to throw a Code Reader on your system and document the trouble codes to see if anything is revealed. You don't say whether or not you have other symptoms of overheating (DexCool issues?) and that leads to this problem as possibly being electrical, then it involves something in either harness , the sensor(s) or the ECM, You need to identify which of the water temp sensors on the engine services strictly the dashboard gauge and examine its connector and the wiring leading from it along the harness to see if there is a short from frayed, nicked or damaged wiring from exposure to a hot exhaust manifold. Be fastidious in your search and rely on feeling along the wire as well as using your vision.

If the ECM is in question... there is one available for your very carline series on eBay for just under $80.00 (and it is a MAKE OFFER listing as well). You might pick this one up or any of the many others being offered from $35.00. Here is the link:

http://cgi.ebay.com/ebaymotors/2001-CHEVORLET-MONTE-CARLO-OEM-ENGINE-COMPUTER-ECU-ECM-_W0QQcmdZViewItemQQhashZitem2a08d8c4aaQQitemZ180537050282QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

Having a "Slight Gasket Leak" on a modern engine is like a man with an infected ingrown toe nail. If he's smart... he'll get his Podiatrist to treat the problem quickly. If not... in six months he will be speaking with the General Surgeon who has to remove his leg below the knee due to blood poisoning and gas gangrene... So the the sooner your LIM gaskets get fixed...the better. With oil floating on the coolant in the radiator... it is entirely possible that your head gaskets need replacing as well. Sorry about this... but to quote The Oracle in the movie "The Matrix'... " ... I hate giving Good People ...Bad News..."

May your "Midi-Chlorins" levels rise to the level needed here...and May the Force be with You... Young Skywalker..."

[pocket-rocket]

Being an 01, I believe it's going to have the single 3 wire sensor. No, the PCM does not disable the gauge when it goes into failsafe. I don't even believe that the gauge is run by the PCM. The 3 wire sensor is like two sensors in one- one for the PCM and one for the gauge. I would wonder if your gauge cluster was bad, but since the PCM is disabling your a/c and the fans come on and stay on I would consider the cluster just fine. I agree with Bob, I would for sure change those LIM gaskets soon, before your Monte becomes another statistic like your fiancee's car and then go from there. I've done a few of those LIM gasket jobs- one of which was before the Felpro steel ones came out. The replacement plastic ones blew out again and leaked tons of coolant into the engine (probably about 5-6 quarts like your fiancee's car). We got lucky on that one since the cam didn't seize, but a number was done on cam journals. The cam and all engine bearings were replaced because we caught it before too much damage was done to render the block useless. That van is still running around trouble free today and this happened a couple years ago.

[skywalker]

Since your car is OBD II, it might be very helpful to stop by Autozone and ask them to throw a Code Reader on your system and document the trouble codes to see if anything is revealed. You don't say whether or not you have other symptoms of overheating (DexCool issues?) and that leads to this problem as possibly being electrical, then it involves something in either harness , the sensor(s) or the ECM, You need to identify which of the water temp sensors on the engine services strictly the dashboard gauge and examine its connector and the wiring leading from it along the harness to see if there is a short from frayed, nicked or damaged wiring from exposure to a hot exhaust manifold. Be fastidious in your search and rely on feeling along the wire as well as using your vision.

If the ECM is in question... there is one available for your very carline series on eBay for just under $80.00 (and it is a MAKE OFFER listing as well). You might pick this one up or any of the many others being offered from $35.00. Here is the link:

http://cgi.ebay.com/ebaymotors/2001-CHEVORLET-MONTE-CARLO-OEM-ENGINE-COMPUTER-ECU-ECM-_W0QQcmdZViewItemQQhashZitem2a08d8c4aaQQitemZ180537050282QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

Having a "Slight Gasket Leak" on a modern engine is like a man with an infected ingrown toe nail. If he's smart... he'll get his Podiatrist to treat the problem quickly. If not... in six months he will be speaking with the General Surgeon who has to remove his leg below the knee due to blood poisoning and gas gangrene... So the the sooner your LIM gaskets get fixed...the better. With oil floating on the coolant in the radiator... it is entirely possible that your head gaskets need replacing as well. Sorry about this... but to quote The Oracle in the movie "The Matrix'... " ... I hate giving Good People ...Bad News..."

May your "Midi-Chlorins" levels rise to the level needed here...and May the Force be with You... Young Skywalker..."

I apologize, it would have made sense to mention, but at least as far as I know the car has never overheated in it's lifetime. I got a leak in a coolant hose back in November and lost a lot of coolant, so it probably ran hot then until the low coolant light came on and notified me (couldn't tell because of the gauge not working), but it's never ran strange or steamed or anything like that.

As for the LIM gasket...got a quote for $1,500 for all the labor involved, and parts for replacing the radiator, gasket, thermostat, etc. Give or take. The car's barely worth much more than that, and I don't have the time to dig into this myself...

Being an 01, I believe it's going to have the single 3 wire sensor. No, the PCM does not disable the gauge when it goes into failsafe. I don't even believe that the gauge is run by the PCM. The 3 wire sensor is like two sensors in one- one for the PCM and one for the gauge. I would wonder if your gauge cluster was bad, but since the PCM is disabling your a/c and the fans come on and stay on I would consider the cluster just fine. I agree with Bob, I would for sure change those LIM gaskets soon, before your Monte becomes another statistic like your fiancee's car and then go from there. I've done a few of those LIM gasket jobs- one of which was before the Felpro steel ones came out. The replacement plastic ones blew out again and leaked tons of coolant into the engine (probably about 5-6 quarts like your fiancee's car). We got lucky on that one since the cam didn't seize, but a number was done on cam journals. The cam and all engine bearings were replaced because we caught it before too much damage was done to render the block useless. That van is still running around trouble free today and this happened a couple years ago.

Yeah...I'll probably be taking this one into the shop to get them to nail down the gauge issue. Between working 60+ hours and a 6 year old more or less as a single father (the fiancee and I work almost completely opposite schedules), I just don't have the time to tear into such an open-ended project.

[pocket-rocket]

Ouch, that sucks. Where are you located? Maybe by chance someone on the boards lives close to you and could help you out and do the LIM gaskets for you. I would hate to see the car go to the shop for something simple like LIM gaskets. I really wouldn't bother with changing anything else but gaskets, unless the radiator, ect are bad. T-stat, sure since it's cheap, but not a radiator or anything like that.

[skywalker]

Ouch, that sucks. Where are you located? Maybe by chance someone on the boards lives close to you and could help you out and do the LIM gaskets for you. I would hate to see the car go to the shop for something simple like LIM gaskets. I really wouldn't bother with changing anything else but gaskets, unless the radiator, ect are bad. T-stat, sure since it's cheap, but not a radiator or anything like that.

I'm about 20 minutes west of Orlando. As for the radiator...just because I don't know if the stuff in the coolant is oil from the engine or tranny fluid from the radiator, I'd want to replace it. It's original equipment with 145k miles on it, so either way it wouldn't hurt...if I'm overhauling the rest of the coolant system I might as well. lol

[bszopi]

I know a guy (and soon to be another) in Pompano Beach who would probably be willing to help out. Not sure how far away that is from you... Hmm, looks like its ~200mi, so maybe not. There are several Florida members on here though.

[60dgrzbelow0]

Say Brad... this is good example of the reason for owner's of similar vehicles to video-document each phase of these repairs when they have any on-going or in-progress repairs with sort of "Follow The Bouncing Ball" kind of instructional videos that describe all the tools, all the gaskets and all consumables and using a video step-by-step approach, document these repairs in such a manner that anyone with modest mechanical skills could follow along with confidence from start to finish! Perhaps www.60degreev6.com could host a video library of such repairs..."Go to www.60degreev6.com... The only site with ""VEESIX VOD REPAIRS" Yes?