How is my car supposed to run?

[firefoot0315]

Okay, this is a little mundane, but I've been curious about it for awhile. Up until about this month, it seemed like my 1994 STS would run great some days and sluggish other days. Nothing that really raised concern, no funny sounds or smells, just a bit less throttle response. I tried to convince myself it was my imagination or state of alertness. Lately though, it's been running exceedingly smooth. While I'm not complaining, I can't really chalk it up to my imagination anymore. Only thing I can figure is I changed my oil about a month ago, switching from Mobil 1 to Pennzoil Platinum, but as an advertising skeptic I don't want to think that's made the night-and-day difference. Has anyone else experienced day-to-day performance differences, and could you shed some light on it for me?

Also, even more mundane, most of you talk about running temps in the 215 range, and worry about 225 and up temps. I've had my car for 10 months, and it's always run at about 226 to 228. It runs great, but should I be concerned?

[Cadillac Jim]

I bought my 1997 ETC new and drove it until I had head gasket problems at 116,500 miles, put in a Jasper, and now have almost 150,000 miles on the car (about 30,000 miles on the remanufactured engine). My experience:

Up through about 80,000 miles, the car always ran smooth. The first few years in Southern CA, the last few in South Jersey, summer and winter, always smooth, always good performance, always good starting, etc. After baout 80,000 miles, the maintenance got spotty; I suspected that dino oil, not synthetic oil, was being used in oil changes, and that the oil was simply being topped off, not changed, and it began to burn oil, then a LOT of oil; this was borne out by the way the engine responded when I would put in a quart or two of Mobil 1. I finally caught the mechanic skipping an oil change and asked about that, hit a stonewall, and changed where I got maintenance. The oil burning went down to a quart about every 2,000 miles and the performance came back and never left, even when the head gasket leak was causing overheating.

What did cause rough idling and lack of throttle response was too much oil burning. Up until 80,000 miles, I changed the oil every 4,000 to 6,000 miles and never added a quart. Suddenly it started burning oil, and a few month later it was burning a quart every 500 miles right after an "oil change" but would revert to a quart every 1,000 miles when I topped it off with two quarts of Mobil 1 -- and the engine would smooth out.

Other things that other owners have reported that can cause smoothness problems include vacuum leaks (including PCV valve stuck open), more than 60,000 to 80,000 miles on the spark plugs (some owners run them past 100,000 miles without problems, though), arcing from the plug wires, breaking down or arcing inside the coils, and issues with the crank and cam sensors (on 2000-2002 models), FPR going bad, sticking or bad idle speed motor or sticking PCV valve, sticking EGR valive or clgged EGR (over 100,000 miles on 1993-1994 model years without an EGR clean-out can do this), too long without giving the EVAP system a chance to purge, dirty MAF or throttle body, and dirty air cleaner element.

Performance won't change much but there are several things that will cause noticeable changes to the more sensitive of to such things. Things that affect performance include synthetic vs. dino oil, 5W-30 vs. 10W-30, altitude, weather (temperature, humidity, barometric pressure), engine temperature (either too hot or too cold), gasoline octane, and carbon buildup.

A cat that has cracked and is slowly going bad could cause your symptoms. It's unlikely, unless you have recently high-centered your car going over a massive speed bump too fast or a high curb in an old downtown parking lot or some such, or the cat has been damaged by a jack or something. But, if you are hearing a rattling down there, you should have the cat checked out.

Penzoil Platinum is a full synthetic, and I doubt that it is enough better or worse than Mobil 1, or that its viscosity or density, hot or cold, would cause the differences you describe. I expect that they used 10W-30 grades for both Mobil 1 and Pennzoil Platinum. I think they changed your air cleaner element or perhaps cleaned the throttle body or MAF the last time they changed your oil. Perhaps you should check the invoice, or ask the people who serviced your car.

[joeb]

have had my 96 for 10yrs. got it with 50k miles. seemed ok at first. did headgaskets 3yrs ago and ran the same before and now. not perfect but pretty close. i have never driven another caddy so i have nothing to compare it with.

[Ranger]

Also, even more mundane, most of you talk about running temps in the 215 range, and worry about 225 and up temps. I've had my car for 10 months, and it's always run at about 226 to 228. It runs great, but should I be concerned?

If those temps are consistent and you are not adding coolant, I wouldn't worry. Might try blowing and then flushing the condenser and radiator fins just to be sure you have good air flow. Also be sure that the splash shield is in place.

[BodybyFisher]

Do you smell coolant when she is warmed up under the hood?

Have you ever changed the thermostat?

Does it run cooler in the winter months? You are in Dallas that is a hot area, those temps are not too bad in the summer, but on a highway, I would like it see it drop to 212

Have you changed the water pump belt?

Are you running the AC? WIth the AC on, the cooling fans run, if the AC is off, the cooling fans only come on at about 226, and then go off at 217.

[firefoot0315]

Jim, I did the oil change myself. But come to think of it I did switch from 10W-30 to 5W-30. That may explain it. Otherwise, I believe my mechanic changed my plugs when he was reconditioning it after 4 years parked (they look clean anyhow), and at a glance the throttle body looks clean. I have suspected a small vacuum leak (sometimes she whistles really high at all throttle levels), but even that hasn't presented in a couple months.

Ranger, splash shield is in place, and those temps are constant. I added almost a gallon of coolant about 4 months after I got the car, but it's held coolant just fine since then. I'll check out the radiator and condensor fins and see if they need cleaning. Wouldn't surprise me after 4 months of commuting a hundred miles a day.

BBF, I don't smell coolant under the hood when she's warm, although sometimes I smell coolant in the cabin first thing in the morning. Got tips in another thread on what to check there, but any other ideas are welcome. No it doesn't run cooler in the winter, it runs around 225, give or take about 3 degrees, year round, highway or city, AC or no AC. I changed the serpentine belt, assuming the water pump ran off that (haven't paid that much attention since it's not given me trouble). I could find out if the thermostat was ever changed, but my guess right now would be no.

[Cadillac Jim]

The water pump is on the back of the engine (driver's side) and is run by the front cam. it is under a cover and has its own little belt and idler wheel. Thus it's totally separate from the serpentine belt system.

If you smell coolant in the cabin you have seepage from the heater core. Make sure that your system has the sealant pellets in it.

[BodybyFisher]

Those temps are higher that I would like to see, I would do this

Drain cooling system

Change the thermostat

Change the water pump belt, its not part of the serp belt its separate as mentioned above

While changing the serp belt check the belt tensioner for binding and LIGHTLY lube the pivot point with ONE DROP of something

Pull out the heater core and replace, if you are smelling coolant in the cabin its a matter of time before it spontaineously blows and spews coolant in the car

Change the cooling system cap

Add coolant making sure its 50/50

Add cooling supplement tablets (4)

While the system is cool, blow high pressure water through the evaporator and radiator to clean it out

Check operation of the cooling fans, with the AC on and AC off

[firefoot0315]

Thank you all for the tips. But this is where my limited mechanical experience runs out and I have a few questions. Where do I find the thermostat and the heater core? 50/50 coolant meaning prestone pre-mixed green coolant? Are sealer tabs available at AutoZone? And by cooling system cap do you simply mean radiator cap?

Also, money is a bit of a concern for me right now. Some of this sounds expensive. Estimates on what a thermostat and heater core might run? And should I be able to do those jobs at home?

Otherwise I'll start with the new water pump belt. That should be simple enough.

[firefoot0315]

Okay changed the water pump belt. Little harder than I expected but that's out of the way. Tried to spray out the radiator, but didn't have much luck. Would it be safe to use a power washer on it? Also added about a half gallon of coolant. Before I did that I noticed a little bit of coolant collected outside the cap. Otherwise all hose connections looked dry. As for the serp belt tensioner, I replaced that last fall. I'm assuming it shouldn't have problems, but if I should still look at it what exactly am I looking for? By pivot point are you talking about the wheel the belt is running over or where it mounts to the engine? Then I checked out the cooling fans. The car wasn't at running temperature, it only got up to about 190, but the fans did kick on when I turned the AC on. I'll check them with the AC off next time I get it warmed up.

[BodybyFisher]

Thank you all for the tips. But this is where my limited mechanical experience runs out and I have a few questions. Where do I find the thermostat and the heater core? 50/50 coolant meaning prestone pre-mixed green coolant? Are sealer tabs available at AutoZone? And by cooling system cap do you simply mean radiator cap?

Also, money is a bit of a concern for me right now. Some of this sounds expensive. Estimates on what a thermostat and heater core might run? And should I be able to do those jobs at home?

Otherwise I'll start with the new water pump belt. That should be simple enough.

Dallas should have some good parts houses, but parts like the heater core, etc can be gotten at www.gmotors.com and www.rockauto.com, your dealer, or a local AC Delco dealer. Look in your phone book for AC DELCO dealers or go to ACDELCO.COM and search for AC DELCO distributors. NAPA is a good chain also.

The heater core is cheap and not hard to put in, but you say you have limited mechanical experience so is might not be too easy. The core is about 30 dollars if I recall.

Buying premixed coolant is a bit of a rip off, you are best to buy a good green coolant and mix it with distilled water yourself. Buy a coolant tester, and test your coolant, its a cheap device, but it will tell you what your coolant concentration is. 50/50 means 50% coolant and 50% distilled water.

I dont know where you can get the cooling supplement but BARS leak makes them along with GM at the dealer. There are six tablets in a pack. Yes I do mean the coolant system cap on the black tank, replace it, if its not holding pressure you will run hotter and loose coolant.

Keep in mind that as you tighten up your cooling system you will "find" other leaks, that is why I say FIX the heater core, it will become the weakest link....

[BodybyFisher]

Okay changed the water pump belt. Little harder than I expected but that's out of the way. Tried to spray out the radiator, but didn't have much luck. Would it be safe to use a power washer on it? Also added about a half gallon of coolant. Before I did that I noticed a little bit of coolant collected outside the cap. Otherwise all hose connections looked dry. As for the serp belt tensioner, I replaced that last fall. I'm assuming it shouldn't have problems, but if I should still look at it what exactly am I looking for? By pivot point are you talking about the wheel the belt is running over or where it mounts to the engine? Then I checked out the cooling fans. The car wasn't at running temperature, it only got up to about 190, but the fans did kick on when I turned the AC on. I'll check them with the AC off next time I get it warmed up.

When I referred to the tensioner, I was referring to the water pump belt tensioner, if it does not apply good pressure to the belt, the belt will slip.

How did the water pump belt look, any cracks, voids, or shiney areas?

Keep in eye on the coolant outside of the cap, it could be leaking OR, you could have a crack in the black tank. That tank holds system pressure and has been known to crack as it ages. your cooling system MUST hold pressure.

I am less concerned with the pulley wheel on the water pump tensioner than I am with the pivot point of the tensioner, the pulley wheel has a sealed bearing in it, rock it with your hand to check for looseness and roll it to check for roughness.. but check the pivot point and put a drop of machine oil, the reason I say a drop is that I DO NOT want you to get oil on the belt

Your fans sound like they are running correctly... good job

[firefoot0315]

I have a few family members who may be able to help me with the heater core, as long as it's relatively simple to get to. The water pump belt looked great. As for the tensioner, it seemed loose to me but I don't know what to compare it to. By loose I mean I was surprised how easily I could move it with my hand, but it seems to keep good tension on the belt. I may stop by AutoZone and see if I can compare it to a new one.

And upon paying attention I amend my statement about the car running at 225 at all times. Driving to work this afternoon with the AC on, it climbed to about 230 on the road and up to 235 at lights. This is after topping off the coolant, changing the water pump belt, and spraying out the radiator and condensor with a little more power at a quarter car wash. Turning the AC off for the last couple blocks, it dropped back to 225.

[Ranger]

By loose I mean I was surprised how easily I could move it with my hand, but it seems to keep good tension on the belt.

You shouldn't be able to move it by hand.

I have a few family members who may be able to help me with the heater core, as long as it's relatively simple to get to.

Why are you changing the heater core?

Before throwing any more parts at it, buy a block test kit from Napa or rent one and test the air in the surge tank for exhaust gases.

[firefoot0315]

Where can I rent a block test kit? Or would my local mechanic probably have one?

[BodybyFisher]

Ranger, do you think he is having an overheating problem due to a bad headgasket? I did not get that impression, he is just running warm, he has not boiled over and he is not complaining of a rough idle/miss.

He is considering changing the heater core because he is smelling coolant inside the car, if he finds a bad cap or tank, due to the coolant he found near the cap, and he fixes that, his heater core is next to go

Rolando, check your purge line. The purge line allows air out of the system. The next time the car is cool, pull the hose off the top of the coolant tank, that goes across the engine while the engine is idling and see if you have coolant flow. It will run out in a stream, if it does your purge line/bolt with a hole in it is clear.

How hot was it today in Dallas?

[firefoot0315]

It was in the mid to upper 90s today. That being said, and with the 10 minute drive home from work still to come, it'll be tomorrow morning before I can check my purge line cool. But I can and probably will run out to AutoZone and look at a new belt tensioner and radiator cap.

[PAUL T]

Before you tackle the heater core, check the hose connections at the heater core. They should be on the passenger side near the top of the firewall. There will be 2 hoses connecting to the heater core. I had a loose hose fitting where the hose connects to the heater core and it was spraying coolant into the heater core area. I tightened the hose and the problem went away.

As far as the car running sluggish at times, are you using the same gas station and same octane level? Different gas stations can make it sluggish at times. Check the air filter also. A few WOT's on the entrance ramps occasionally would not hurt also. This keeps the carbon from building up in the engine.

[firefoot0315]

Good call Paul. Doesn't hurt anything to check the little things first. Thanks.

As for gas, I usually either go to QuikTrip or Walmart. For awhile I went down to 89 octane gas but have gone back to strictly 93 the past couple months. Didn't see much immediate difference between the two though. I have considered that it is where I get my gas, but I figured those places wouldn't be using substandard gas and haven't put that much thought into it since. Might start keeping better track. And way ahead of ya on the WOTs!

[BodybyFisher]

I am very interested in the outcome of this. I was thinking of this thread when I was out driving before.

The next time the car is warmed up to operating temp, squeeze the upper hose and see if you are holding pressure and how hard the hose is. Your water pump tensioner seems a little weak. How did you put the new belt on, did you move the tensioner with a wrench or by hand?

[firefoot0315]

I put the belt on by hand. Went by O'Reilleys asking about it, and as the manager put it, "Not even Lou Ferigno should be able to move that by hand." Unfortunately, looks like only the dealerships carry that belt tensioner anymore. I may try to find a good one in a salvage yard, because I'm not ready to spend a hundred bucks on a new one.

Checked the purge line this morning, it was flowing. Also tested my coolant mixture. My tester isn't gauged in percentages, but rather freeze and boil over points, but it's at least 50% coolant. As for the upper hose, there wasn't much of a pressure difference between running and off. Still a little drip of coolant under the overflow line when I start it up, but that seems to dry out.

[BodybyFisher]

How did the old WP belt look, do you still have it? Was is shiney? I don't believe that you should be able to put that belt on by hand, but I never tried, I used a 1/4" breaker bar. Check gmotors.com and rockauto.com for prices on the WP tensioner

Continued evidence of coolant at the top of the tank is evidence of a problem

The hardness of the upper hose, is when it is UNDER PRESSURE and when its NOT UNDER PRESSURE, it has nothing to do with whether the car is running, does it feel hard when the system is up to temp? The system holds 16 to 18 psi and that hose should get hard if your system is holding pressure

It sounds like you are doing good with your diagnosis, next, change your thermostat. Don't forget to buy the thermostat rubber seal also. Its a two bolt operation, 13 mm socket, if I recall. Very easy job to do... the hardest job will be getting to it, remove the air filter box (gently), remove the lower hose from the stat housing, and remove two bolts, the long tail of the stat goes inward. Reverse to install here are some photos. Some photos show the water pump cover off, you do not need to take the water pump cover off to change the thermostat....

[firefoot0315]

I'll look into the thermostat tomorrow morning, after I recheck the hoses when they're cool. May just go ahead and pick it up tonight so I can work on the car while it's cool. 16-18 psi sounds about right for how firm the hoses were hot. I just changed out my radiator cap, hopefully that will cut out the coolant puddling at the overflow line. The old belt looked just fine, not really all that much worse for wear than the new one. I actually ended up removing the belt tensioner to get the belt off, missed the gap between that and the engine (durr durr durr), but before I removed the tensioner I was able to get the belt unlooped from it by hand, which more and more people are telling me I shouldn't be able to do. By chance does anyone here know the spec for how much the belt should give? Thanks for the photos.

[Ranger]

Where can I rent a block test kit? Or would my local mechanic probably have one?

AutoZone should have them for rent.

Ranger, do you think he is having an overheating problem due to a bad headgasket?

Not necessarily Mike, but I recall that the temps seemed to be climbing a bit higher with each post and I think he added coolant once or twice. I have gotten a bit callous though. Anytime I hear overheat on a Northstar, if the problem is not obvious, I kind of like to eliminate the most probable first, rather than chase ghosts and let guys throw parts at it. I've seen too many guys change every component in the cooling system before figuring out the inevitable. Like I said, I'm not necessarily sure that is his problem, but why not rule it out right away.

He is considering changing the heater core because he is smelling coolant inside the car

I must have missed that.

[BodybyFisher]

Thanks Ranger, I understand, I tend to move up the diagnosis tree, you are eliminating HG immediately.