I have an 03 Monte Carlo SS, 131000 miles, 3800 series 2 v6

Okay so now that it's cold out in Jersey, I noticed that the car never heats up I mean never heats up no matter what. Even after hour drives. It never goes past maybe a third of the way up on the temp gauge. I'll list the symptoms in list form.

1. Car never heats up
2. Heat takes forever to warm. And is never Hot.
3. Transmission stays in each gear longer and doesn't go into overdrive. until the temp gauge passes the lowest line (140)
4. Gas mileage is reduced.
5.Whatever heat the coolant does build is quickly lost when car starts moving again such as at stop lights.

Now this is what else I noticed.

1. Both the upper and lower radiator hoses are within 10 degrees of each other at all times. (irrelevant maybe Idk lol)
2. Both heater core hoses are the same temp as well
3. I noticed the radiator was low so I put fluid in and then noticed a large damp puddle under the driver's side radiator. After 10 mins of idling ( it was about 3/4 of the way full when I started)
4. All around the intake manifold is wet. Assuming the intake manifold is the big round plastic thing on top. I wiped some off and smelled it. No distinct smell.
5. Engine seems extra loud and hissy.
6. radiator and overflow tank and radiator cap all have this cakey light brown gunk on it. Has kinda of a dirt smell to it. Doesn't smell like oil or anything. Overflow tank is so bad you cant see into it to fill it correctly.

Things I didn't see.

1. No excessive white smoke
2. No reduced performance (that I noticed) besides mpg
3. Oil was dirty but looked normal

I read about thermostats being stuck open, the common intake manifold leaks. I'm pretty sure the radiator leaks but is that the only problem? Can someone lead me in the right direction thanks?

Possibly related: the cat converter went a year and a half ago. My step dad had it replaced. Just mentioning it because i heard that thermostats being stuck open and can blow cats from having to run rich all the time.

Just for my own Knowledge I've been reading two different things about thermostats. Few say that they fail open by design. And then others say they rarely fail open. Which is true?

Thanks again.

 

First things first, you said after filling the radiator you had a puddle on the ground. Pending you did not spill, sounds like a leak. Find and fix the leak. This will impact your heat inside the car and various performance measures the PCM uses when the car hits operating temp.

Best way to find the leak is borrow a radiator pressure tester from your local parts store (then you can pressurize the system without it running and look/listen for leaks safely).

 

UpDate: I just drove the car for about 20 mins and now it heated up fine. What is going on here??? The fluid I put in must have did something (even though some of it leaked back out). How is that when I'm low on coolant the car doesnt heat up. But when I add coolant it heats up quickly?

Shouldn't leaking coolant cause the car to overheat? Why is the opposite happening?

@maniac: Yeah it definitely was a leak because I was filling on the opposite side with a funnel. The puddle was on driver's side

 

If you have a owners manual for your Monte find the section that references complete coolant change. Does it have a statement in this section of the owners manual about with a complete coolant change to add a supplement?
My 1996 Monte has the statement as well as my 1996 LT4 Corvette. I always change my own coolant and also add the supplement when I change the coolant.


The supplement will produce the "brown gunk" you mentioned. The supplement I have been told was used at the factory when the cars were built. It is a leak sealant, having cast iron blocks and aluminum heads sometimes need help to prevent leaks.


The supplement comes in the form a tablets, GM sells them and they can also be bought in auto parts stores as BARS LEAKS part #HDC. Comes in a blister pack of 6 tablets.

 

I'll definitely look in the manual if I can find it.

I'm wondering if I unintentionally bled the system by removing the radiator cap. There was some bubbling as I put the fluid in?

When I put it in the radiator filled up then bubbled back down so I put more fluid in until fill it.

 

Your interior heat is directly related to the coolant. If the system is too low on coolant, then there is not enough coolant to properly circulate into and heat the heater core which is used to warm the inside of the car.
Temp gauges for coolant best measure the temp of coolant (as I understand, air pockets in the cooling system can cause the temp gauges to to sometimes read a little crazy).
When you overheat the engine, it is because a situation existed to literally overheat the engine (typical cause is lack of coolant). I'm trying to think the best way to explain it. Coolant helps absorb the heat from the engine and move it, your radiator and radiator fans assist in trying to re-cool the coolant to go back to the engine and absorb more heat. If this does not happen, the engine will over heat. When you have nothing but air moving through your coolant system because it is low or empty, air does not absorb/transfer heat the way coolant does (hence again why your heater core is not hot enough to blow warm air into your car).

Find and fix the leak. Go to the parts store, do a loan-a-tool on a radiator pressure tester. When the car is cold, connect the pressure tester to the radiator. Pressuring to about 12-15 psi should be enough to look and listen for a leak (you may see it bubbling or hear it hissing).

I do not recommend putting "stop leak" products in the car's system (I don't care if it's GM or another manufacturer's product, just a bad idea). Find and repair the problem.

On the driver side, the only things on a 3800 I can think of that would make a puddle on the drive way while filling the system:
- Bad hose
- Bad gasket on the coolant bypass for the lower intake
- bad radiator
- radiator drain plug left open

There are a few others, but it would be best to pressure test the system.

 

@Maniac

Hey maybe I didn't make myself clear. But when I'm saying the car isn't heating up. I'm talking about the temp gauge on the dash. I'm not talking about the cars interior heater. The actual temp guage itself never goes up (according to the temp gauge.)

I went on an hour long drive the other day and the temp never rose above maybe a third. And when I started driving again after stopping at a red light. The temp gauge would go down to maybe a 1/6 just a little above the 140 marking.

My engine is having an under-heating problem not an overheating problem.

That's what I don't understand. The car never gets up to operating temperature.
My cooling system is over-cooling the car not under-cooling.
So my question is how is that when I'm low on coolant the car doesn't heat up according to the temp gauge. But when I add coolant it heats up quickly according to the temp gauge?
Sorry for the confusion

 

Is the transmission shifting slower and not going into overdrive a way for the car to warm itself up faster?

I'm getting fed up with it and I'm about to replace the radiator, hoses ,thermostat and overflow tank. good idea? probably needs to get done anyway.

 

[QUOTE=The_Maniac;633426]Your interior heat is directly related to the coolant. If the system is too low on coolant, then there is not enough coolant to properly circulate into and heat the heater core which is used to warm the inside of the car.
Temp gauges for coolant best measure the temp of coolant (as I understand, air pockets in the cooling system can cause the temp gauges to to sometimes read a little crazy).
When you overheat the engine, it is because a situation existed to literally overheat the engine (typical cause is lack of coolant). I'm trying to think the best way to explain it. Coolant helps absorb the heat from the engine and move it, your radiator and radiator fans assist in trying to re-cool the coolant to go back to the engine and absorb more heat. If this does not happen, the engine will over heat. When you have nothing but air moving through your coolant system because it is low or empty, air does not absorb/transfer heat the way coolant does (hence again why your heater core is not hot enough to blow warm air into your car).

Find and fix the leak. Go to the parts store, do a loan-a-tool on a radiator pressure tester. When the car is cold, connect the pressure tester to the radiator. Pressuring to about 12-15 psi should be enough to look and listen for a leak (you may see it bubbling or hear it hissing).

I do not recommend putting "stop leak" products in the car's system (I don't care if it's GM or another manufacturer's product, just a bad idea). Find and repair the problem.

On the driver side, the only things on a 3800 I can think of that would make a puddle on the drive way while filling the system:
- Bad hose
- Bad gasket on the coolant bypass for the lower intake
- bad radiator
- radiator drain plug left open

There are a few others, but it would be best to pressure test the system.[/QUOTE

What is your reason or reasons for not using what is written in my owners manuals for using the supplement with a coolant change for my 1996 LT4 Corvette and for my 1996 Monte Carlo? Have had my LT4 Corvette sine it was new and have had no problems using the supplement since 1996 with my coolant changes.

 

I agree, I don't recommend putting "stop leak" products in the car's system So one of the Techs that works on my Car showed me an engine he had torn down. It was abused and also they had used a stop leak stuff in the coolant system some of them have some metal fibers in it looks like the iron filings you pick up with a magnet in dirt. I have used it but in an old Hunting car that I use and don't care if it lasts or not.
That all said I always flushed the system every 25K and usually changed the hoses every year but I was at one time doing 50K per year. I ran one 3800 to 389K miles and it was still good but the Computer went out and with that high a miles it usually doesn't work to replace it.
You may have a defective Gauge, my son in law let me use his 01 Monte for a few weeks and it always shows a low heat range, but it all worked and it ran fine. I always had to supply my own cars for the travels I did and the maintenance, it was my costs, so I always replaced the normal maintenance items regularly with new. The reservoir tank you can take out and clean. You are getting some good advise from the other MCF members. Hope you have good luck.