Thread: So, I need advice from someone with functional knowledge (car-related)

Originally Posted by TheBaschnagelnator

I'm doing extensive work on my 1995 Monte Carlo tomorrow in my garage. I'm replacing my water pump, radiator, and thermostat housing. I've never flushed and refilled the cooling system on this car before (recently bought it), but it has TWO bleeder valves...one on the t-stat housing, and the other is above the water pump.

My question is..does anyone have any prior expertise with these mid 90's 3.1's with regards to bleeding the air out of the cooling system? Do I open BOTH valves at the same time, then fill with coolant until only coolant spews out of the valves? Or should I open the valves, RUN the car, then fill more coolant until fluid leaves the valves as the car is running? I know either way to turn the heat dial to the hottest point (but not turning the fan on) inside my car when doing this.

My Chrysler was different as I simply had to squeeze on the upper rad hose.

I wanna be careful with this process, because excessive overheating and blowing my head gasket would take the taco.

I'm fine with the hardware replacements, but I just want to be better prepared for the refill/bleeding stage. Conflicting directions has my head spinning. I'd rather get directions here if possible, simply because I could reply for further clarification.

Thanks in advance.

My first question is to ask why you are doing all of this work at one time on your car. The reason I ask is that the 3.1 is known for an internal coolant leak that can result in extensive engine damage. I've owned two and both had the same issue, both engines ended up dead a few months after fixing the leak. It is caused by the manifold having a seal that joins the block and the heads. This three part seal is known for leaks.

If you are having troubles with the car overheating, or your temperature gage getting hot (with no heat coming from the vents in the car) and then dropping to normal (with heat then blowing through the vents) along with an unexplained coolant loss, or no loss and "sludge" in your coolant, then this might be the case for you. It's not a radiator/water pump/thermostat issue. It's due to the leak and the way the coolant system is set up, as soon as the coolant gets a little low (even without showing on the gage in the car) it won't blow heat and will look like a water pump issue.

The result being that you need to replace a manifold gasket instead of the radiator/water pump/thermostat, and I would recommend getting rid of the car as soon as you do. If there has been any time lapse with a coolant problem on that motor it's inevitible that it's on it's last leg sometime soon.

Originally Posted by blinddeafmute

My first question is to ask why you are doing all of this work at one time on your car. The reason I ask is that the 3.1 is known for an internal coolant leak that can result in extensive engine damage. I've owned two and both had the same issue, both engines ended up dead a few months after fixing the leak. It is caused by the manifold having a seal that joins the block and the heads. This three part seal is known for leaks.

If you are having troubles with the car overheating, or your temperature gage getting hot (with no heat coming from the vents in the car) and then dropping to normal (with heat then blowing through the vents) along with an unexplained coolant loss, or no loss and "sludge" in your coolant, then this might be the case for you. It's not a radiator/water pump/thermostat issue. It's due to the leak and the way the coolant system is set up, as soon as the coolant gets a little low (even without showing on the gage in the car) it won't blow heat and will look like a water pump issue.

Well, what originally happened was I would only overheat at idle. So, first I replaced my thermostat two weeks ago, but I broke off the bleeder valve on the t-stat while attempting to open it (this is common on these cars). Later in the week, I the car began overheating again, but it also had a higher than normal rpm (would start above 1000 and fluctuate up to 2000 at idle), so I let the shop check it out and diagnose, because I couldn't figure out what had happened..I had a broken seal at my fuel injectors. It caused the injectors to over-work, and thus overheat. So, I got the car back some 2 hours later.

Not long after that, I noticed that I had a slow coolant leak where the upper rad hose meets the t-stat housing, along with a nasty leak along the side wall of my radiator.

I picked up a radiator, U/L hoses, and t-stat housing...but since they are very easy to swap in the '95 Monte's, I also bought a new water pump. (I know you said you are familiar with the 3.1's but I'm just posting the pic for all to see)




So, this is why I did the water pump, too. It was inexpensive and convenient to do. I wanted to get the new t-stat housing to replace the bleeder valve and possibly address the upper hose leak (which is why I also just swapped the hoses). The radiator was easy to change. Except, that I made it a tad harder than it should have been..I mounted the fans onto it once the new radiator was already installed.

The timing belt was fine, and the old coolant was appeared normal. The car has 178,000 miles on it, so I'm vigilant when it comes to preventative maintenance. So far, the repairs seemed to have done the trick. The car is running strong and the temp issues have been normalized (hopefully not temporary). Since I bought the car in the late spring, I've repaired the following: PCV valve, serp belt, plugs/wires, brakes/rotors, outer tie rods, lower ball joints, power steering pump/pulley, rad hoses, water pump, radiator, t-stat, t-stat housing, multiple gaskets, O2 sensor, 2 oil changes (new oil filter per change), new air filter. At the shop, I had the injector seal repaired, and a high pressure power steering hose replaced, new tires and alignment.

No signs of a head gasket issue, either. I knew it wasn't that. The HG and timing belt were the first two things I wanted to make sure were in working order.

But as of this morning, the car is doing great. No leaks now, and runs like a champ. I will keep you guys posted, though. I'm not saying I'm out of the woods - I know better. I will continually inspect the car for issues related to the cooling system.

I'm in OT school til the fall, and am unemployed by choice during school. My wife is a nurse and she is temporarily taking care of me. She's a saint. So, for now, I want to stay on top of things with the Monte Carlo. Especially, now that its cold out (I park it outside..she gets the garage lol)

Originally Posted by vmx12

I used to be a mechanic but not very familiar with this car. Best bet is to find out the right amount of coolant for the vehicle and fill with both valves open. As soon as they start to leak fluid close them. Probably be the water pump first since it is lower on the engine. Make sure majority of coolant is in engine before running.

Also found this for you.
Monte Carlo Forum - Monte Carlo Enthusiast Forums

I did open the bleeders, like you recommended. It did have an initial problem in the early stages of re-filling. I continued to have issues with trapped air for a short time, I believe. When I first started the car, the heater wouldn't blow warm, and the guage read that I was over-heating, yet I could set my hand on the top of the engine without being burned. So, the motor was not overheating as the gauge said. I turned my heater off to heat up the motor, ignored the gauge, and tried to truly get the motor warmed to better circlate the new coolant. I would also "milk" the car at the rad hoses to remove any remaining air pockets as the car would run idle. I would also continue to top the coolant off at the radiator. Despite all of this, I would get the "low coolant" light a few times.

The gauge then went back to normal, and the heater started to blow warm. The "low coolant" light turned off, and I drove the car home from my mom's garage. During the first 5-10 minutes of driving, the gauge started to show overheating and the "low coolant" light popped on 2 more times, but then it went to normal. I drove the car 30-40 more minutes and it was perfect. No lights, no goofy gauge readings... nothing.

So, I guess it just had to work out the kinks while I drove it. Hopefully.

Thanks to the both of you for keeping in-touch and offering help.

Originally Posted by blinddeafmute

The result being that you need to replace a manifold gasket instead of the radiator/water pump/thermostat, and I would recommend getting rid of the car as soon as you do. If there has been any time lapse with a coolant problem on that motor it's inevitible that it's on it's last leg sometime soon.

And, I will doubly check for any issues with the manifold gasket. And I'll heed your warning if there is an issue there. Ill get back to you soon...I'll prolly do that today.

Not jumping ahead of myself here (still have to inspect my car for this), but I subscribe to this YT channel. Scotty Kilmer has some good stuff for car repairs. I recommend him for anyone that needs a reference

Here's him replacing the manifold gaskets. Doesn't look that bad

granted this is on a 3.4l grand am BUT its the same motor as the 3.1l gm put in a lot of cars in the mid 90s. so MOST of these steps should be identicle, inclueding bolt sizes. i've actually done this LIM (lower intake manifold) gasket on my car 2x. i need to do it a third now, as its leaking oil, again.

here is a STEP BY STEP walkthrough on how to do it on this motor.
LIM and Head Gasket Change Walkthrough/FAQ - GrandAmGT.com Forum

note line 57
57.) Fill the coolant reservoir up to the "full cold" mark and then squeeze the upper radiator hose to start getting the air out of the coolant system, then refill up to the cold mark

no bleeding required, just like on your chrysler.

good luck, if you have any questions feel free to ask, but the last time i did this was 08, so its been a while.

Originally Posted by Metallman56

granted this is on a 3.4l grand am BUT its the same motor as the 3.1l gm put in a lot of cars in the mid 90s. so MOST of these steps should be identicle, inclueding bolt sizes. i've actually done this LIM (lower intake manifold) gasket on my car 2x. i need to do it a third now, as its leaking oil, again.

here is a STEP BY STEP walkthrough on how to do it on this motor.
LIM and Head Gasket Change Walkthrough/FAQ - GrandAmGT.com Forum

note line 57
57.) Fill the coolant reservoir up to the "full cold" mark and then squeeze the upper radiator hose to start getting the air out of the coolant system, then refill up to the cold mark

no bleeding required, just like on your chrysler.

good luck, if you have any questions feel free to ask, but the last time i did this was 08, so its been a while.

Very helpful information. Thanks. And I will come and ask you questions at some point in the near future. I kinda want to just go ahead and replace the intake manifold gaskets. The car is doing good now, but at 178k miles, those have not been replaced by the previous long-time owner.

The other thing I want to do is go back and clean my throttle and check the MAF sensor; then I'm going to do the "cigar trick" to check for any vacuum leaks. My car does great while its moving, but in idle, it tends to run a little rough. I replaced the plugs/wires and PCV not too long ago, so I'll see what happens. Heres the cigar trick if you've never heard or tried it. Pretty cool..

if your going to do the gasket replacement just wait on the thermostat, because your going to have that apart anyways. its not the easiest thing to replace, so just wait until your going ot be in there.

i had a vacume leak once. the hissing was crazy, and the car ran like crap. i forgot to clean the UIM gasket off the LIM. caused a bit of a leak.

as far as rough idle that could be anything. i would start with plugs and wires, if cleaning the buttlerfly in the throttle body, and maf doesnt work. if you even have a miss its either plugs, wires, or coils. atleast thats been my experiance in the past 8 years and 100k + miles.