Mechanics: 1999 Alero overheats when cold outside

Factual Questions
1

My 1999 Olds Alero V6 3.4L (automatic) has been overheating and losing coolant when it is cold outside. I haven’t determined an exact cutoff, but let’s say anywhere below 25 degrees F.

At first, it just seemed to be losing coolant slowly and once in awhile the low coolant light would come on. Then once in a while (now more often, I think), when it was cold there would be a catastrophic coolant loss and the reservoir would be dry in the morning. I don’t know if this was due to coolant loss while driving home the night before, or loss while sitting there getting cold all night. The worst it happened was when it was about 11 one night but this morning it ran hot all the way to school and it was about 6 outside. I have not noticed any puddles under the car.

The thermostat and reservoir cap have been replaced. While the car was running at high-normal (higher than normal but not overheating) operating temperature, I looked and both fans were running. All belts seem to be tight. I don’t notice that the oil looks wrong other than being dark brown like it needs to be changed.

When the car overheats (or even runs hotter than usual like it did on the way to school today), I can hear a boiling noise from the vicinity of the reservoir tank and see steam coming out of the area. At the same time, the heat inside the car does not work. If the car is not overheating, the heat inside the car may take a little longer than it used to, but it works fine once the temperature gauge gets above half. The car has never overheated twice in a day. If I wait for it to cool, add the coolant to make up for what it boiled off, then drive it again it seems to be fine.

The coolant is the kind that claims it is compatible with all coolant colors (Prestone brand lately, but I have also used Peak) and is rated to -34 F so I don’t think it gets frozen in there. Does the wind chill count in this instance? Say I am driving 55 down the road and it is 6 degrees outside. Is that like a 55mph wind that would bring the temp down to a level where it could freeze? I wouldn’t think so, since people are driving around much further north than me with the same coolant I have.

There is a little bit of brownish to black gummy looking sludge around the top of the reservoir tank but it has not changed noticably since this all began. I think it has been there since I got the car a year ago but I couldn’t say for sure.

I have been reading about lower intake manifold gaskets and head gaskets often causing these problems. Does this sound like one of these? Something completely different? My dad has been working on this as much as possible, but we are running out of simple options and I need to know whether to call a professional in.

Thanks, car Dopers! I wish this was like a dog or cat where I could just run some blood tests and get some xrays and know a lot more about what is (and isn’t) going on.

2

The overheating, boiling noise, steam, and lack of heat are from a significantly low coolant level. Find and fix the leak - this may require a professional’s equipment and expertise. Once there is no leakage, and no air pockets in the cooling system, I venture you’ll have no problems.

Type and brand of antifreeze are not affecting this situation.

Wind chill is not applicable. Wind chill does not make the actual temperature lower. It’s a way of comparing the rate of heat loss, the idea being that if it’s, say, 40’ with a wind chill of 25’, your body will lose heat (get chilled) as fast as if it were 25’, but doesn’t mean it will actually be 25’. It’s still 40’ outside and nothing will get colder than that.*

*Yeah, I know radiant heat loss, but not germane to this topic - keeping it simple.

3

If your temp gauge reads hot, and the heater blows cold you are either low on coolant or its air bound.(when air bound it is also low).
When you add coolant you can slowly squeeze the upper radiator hose while maintaining a full radiator. I am not necessarily talking about the coolant reservoir, as most will only maintain a system. You have to access the radiator.

Also on many cars there is a small bleeder. It will usually be brass and is on a high point of the thermostat housing. Open that small valve while filling and maybe even upon starting the engine. I will open and close this small bleeder while squeezing the upper hose.

4

Thanks for the info! All of this does make sense. I really thought there must be air somewhere but I have no idea where it could be coming from.

The system was bled when the thermostat was changed a few weeks ago but I had several low coolant incidents since then and there was probably a lot more air introduced into the system. It just puzzles me why this only happens when it is really cold outside.

I really wish I could access the radiator. I am pretty sure there is no radiator cap on this model.

5

Confusion comes from using the term “reservoir” for both expansion jars and surge tanks. Expansion jars are external to the pressurized cooling system, beyond the radiator cap. Surge tanks are integral to the pressurized cooling system and generally the site of the pressure cap (“radiator” cap, even though it’s not actually on the radiator). Surge tanks are like a see-through extension of the radiator. This car has a surge tank.

While it’s great, and necessary, to get any air out of the system when refilling, it’s an exercise in futility when there’s a leak, which will simply let more air in. In this case it appears that there is indeed a leak, and frankly there’s not much point in doing or worrying about anything else until the leakage is fixed.

6

Check the expansion reservoir and the hose to it for a crack. A crack there and the coolant will leak out and not be there to get sucked back into the radiator when it cools. After a few trips you have low coolant in the radiator.

7

Good advice for cars that have expansion jars. Not applicable to this car, which has a surge tank.

8

My plastic coolant holder, (which I have now learned is a surge tank), is intact, as are all hoses that I can see. As I read about the Alero, I am getting more convinced this is not just a coolant system problem.

My dad has decided to tackle the project himself and go for the lower intake manifold gasket, apparently a famous problem in this car. While he’s in there, he’s going to check out the head gasket. He has the manual and is studying up, but the last time he did something like this was in the 80s. He said he will be able to do it, just much more slowly than someone who does a lot of these. (And it’s a good excuse for me to buy him some torque wrenches!)

While I’ve got the attention of the car crowd, are there any common novice mistakes he should watch out for? I do trust that if he didn’t think he could do something like this, he’d send me straight to a mechanic.

Many thanks for the info so far!

9

The one that comes to mind is “Gasket Scraping”. its not like the old days of cast iron components. 1 little slip will cause a very big problem.

There are special gasket removing tools that are made for alloy components,
This link describes what was used 10 years ago and today there are even better discs that are more forgiving, not to say one cannot do a good job with these, if skilled enough.

Then this link,

I have to try that one myself.:wink:

10

Have you checked your heater core? It’s a pretty common place for cars to develop a leak. After running your heater for a bit, check your floorboards for dampness. If there’s water there, you likely have a heater core leak. If there’s not, you may or may not have one.

If it turns out to be so, you can often easily bypass the core until you can get a new one. Of course, you won’t have heat (but then, you don’t have heat now…) A new core for your make and model should cost between 40 and 100 bucks, depending on what kind you choose.

Hope it’s something simple like that. Have fun working on it with your dad.

11

[quote=“SoulFrost, post:10, topic:481717”]

If it turns out to be so, you can often easily bypass the core until you can get a new one. Of course, you won’t have heat (but then, you don’t have heat now…) A new core for your make and model should cost between 40 and 100 bucks, depending on what kind you choose.

QUOTE]
Heater cores.

I replaced a leaking one once. And of course about a week later the NEW one developed a leak :frowning:

In theory replacing a heater core is a simple task. A few hoses and clamps and your done.

However, many cars, both old and modern, require you to virtually take the interior of the car apart to get to the damn thing. If you don’t know the tricks to taking the interior apart, it can be pretty easy to mess up other things like wiring or the AC system or the interior itself in an attempt to get to the easy core.

Click and Clack had a good recommendation the other day. Some guy wanted to replace his heater core. The told him to go to a junkyard and find his model of car. If he was able to remove the core in the junkyard with the tools and knowledge he had, then would be able to do the same with his car. Of course he would have to pay the junkyard something for their trouble, but given how horrible those things CAN be to get to, its probably a little money well spent.

12

Heh. True.

But I only said it would be easy to bypass. Changing it out may be another matter. I just figured that if Dad was adept at head gasket replacement, he’d know what he’d be doing.

13

Thanks for the added replies. I was at my parents’ house (where there is crappy dialup) dropping my car off, helping buy parts, and picking up a rental.

I’ve got no damp floorboards, except where my now ever-existent bottle of spare coolant leaked a bit onto the backseat floor. There are coolant puddles under the hood in classic intake manifold leak patterns. I wish it was a heater core!

Sadly, I don’t have time to work on this with my dad. He lives a couple hours away and I am finishing up vet school. I was lucky to get a consecutive day and a half off this weekend. I’d like to learn how to take apart an engine. With all the problems my cars have had (and will have) over the years, it almost seems I will at least be able to diagnose most problems by the time I am too old to drive!

I’ll pass on the advice about scraping old gasket gunk off. I’m sure anything that involves me buying Dad another tool will be just fine with him. He might even have something like that laying around, who knows.