I'd be checking for debris in front of the condenser and radiator. after buying mine I found a candy wrapper, weeds and feathers. 250 is time to start getting concerned

 

Where is the unit? Is the unit easily accessible? Do I get to it from top or bottom?
Interesting thing is that this has never happened before. Sure I've seen coolant creep close to 230 on the hottest days, but then again, I've never sat in traffic on a day the likes of what hottie did yesterday. And, why would it magically come all the way back down when the ambient temps only dropped 10 degrees? If it was an air bubble or blockage I would think it would happen more often. I'm thinking it HAD to be the situation she was in.

But, I will press on, just in case it is something else that's really wrong. I don't see how an air bubble could get into the system, unless they can form on their own. Thoughts? I will be checking for blockage in 5 minutes.
Thanks for the info. Oil looks was recently changed and still looks good when I pull the stick.

And, for a limited time.....

Does she qualify, or is it just me?

 

I'd have to say that your coolant temp was way too high - even in stop and go traffic it shouldn't get past 230-235 or so. Could be a stuck thermostat, fans not kicking on properly, or even debris in the radiator air path.

 

I've got a 160 stat and re-programmed fans. My car never sees 190, ever...

 

OK, went to clean the radiator and ac unit. While there were no large items, I used my compressor and got out about a tablespoon of debris. Then, I decided to tap lightly on each unit to see what would happen. And, IT HAPPENED. A sandstorm came down upon me. Good thing I was wearing a mask and safety eyewear, which I NEVER do, but ALWAYS will from here on out. I ended up tapping all over the units for nearly 1.5 hours. Yep 1.5 hours!

Here's what came out:

10 inch x 10 inch pile of sand! Note that this pile doesn't look it, but it is over 1 inch tall, too. I probably could've tapped more out, but I figured I'd keep some of it in the units' fins for posterity.

You guys think this could've contributed to the problem? I also topped off the coolant tank which was a bit low, but not empty.

 

Definitely! It's amazing what the radiator picks up.

 

I hope that was it. I mean, I think it probably was the culprit, which is why it took so long to cool down once it hit those highs. And, from what I saw, once it did cool down from a 5 mile run at freeway speeds at a 10 degree lower ambient temp, when I hit city streets again, it did climb back up to the 190's quicker than usual.

I think that the sand may actually be WORSE than leaves and grass and the like, because dirt and sand hold heat, so if there was enough between the fins it could defeat the purpose of having fins for cooling, and the fans aren't strong enough to cool the radiator AND the amount of sand that was in the fins. Does that theory sound about right?

Also, can somebody tell me WHERE the oil pressure sending unit is located?

 

Yeah, sand embeds itself into the fins and will cause a complete blockage of airflow.

The oil pressure sensor is behind the intake under the cowl. There is a sticky in the Tech section about these sensors.

 

Oh, great, then I bet it's a biatch to change it out. I guess I'm in the hunt for some tips, huh? I'll check out the tech sticky to see if there are any instructions (or prayers). :-(

 

I didn't like seeing over 220 degrees on my 03 coupe, so I took her to the Chevy dealer. They checked her out and said she was fine. They gave me a service bulletin that basically says the low speed cooling fan comes on at 226-and goes off at 219. The hi speed fan comes on at 235, and turns off at 226. When the a/c is on and coolant reaches 185, the low speed fan kicks on at speeds of less than 35 mph.
If coolant exceeds 256 there will be a coolant over temp indicator in the message center. The IPC will also illuminate the check gauges and a chime will sound.
That sounds pretty hot to me, but he said don't worry about it until about 245 or so. Hope that helps.

 

Yes, this helps. I at least now know what is safe and what is not. Which means I was poosibly darned close to a new motor.

 

I wonder if the Romo and the cowgirls are out in that heat since there indoor practice facility fell down- Redskins forever

 

Sometimes a 160 degree thermostat can be a bad thing, it can let the coolant circulate through the radiator too fast and therefore it won't cool down enough.

 

OK, it's been over a week now, and no more problems, even in the heat.

From this experience I've learned that even if you don't see any visible blockage, there absolutely WILL be very small pieces of road grime, such as sand and gravel lodged between the fins of the radiator, which you can NOT see, and the only way to clean it out is to tap the radiator lightly with a rubber hammer.

However, there is a specific method you must employ to find it and clean it out, because you cannot see it, it is not easily accessible, and an air compressor will do you no good. While you do not need to remove the shroud itself, the first time you do this, I recommend that you remove the top shroud cover, so you can see what's going on.

There are channels that run the length of the radiator, top and bottom, which is what you should tap on to dislodge the debris. With that said, you should know that even with light taps of a rummer hammer, the ridges of the channels are susceptible to being bent. The best thing to do is to slip a piece of wood into the channels, between the ridges of the channels and tap on the wood.

Note that the debris will fall out, but will not hit the ground, so you might not think there's much debris. Because of the angled position of the radiator, the debris actually falls backwards into the bottom of the fan housing, which is why you may not think there's much debris. You should then lightly tap the back of the fan housing, and debris will rain down out of the fan housing like you wouldn't believe.

Based on the angled position of the radiator, it is no wonder dirt and the like get caught between the fins, and I would venture to guess that every single C5 accumulates debris, the likes of what I saw, regardless of where you live. The interesting thing is that this debris can collect over time without you noticing it, and instead of your car getting gradually hotter over time, it can "magically" just zoom to an excessively hot state all at once.

While this is a relatively easy thing to remedy, as far as difficulty is concerned, it can be extremely tedious if you wait too long, and you can end up tapping for hours, like I did. I fact, I ended up stopping after an hour and a half because my muscles were aching by then, even though a bit of debris continued to fall on each tap, albeit by that time the amount that fell on each tap was significantly reduced. As such, I recommend that you do it once a year, twice a year if you live in a rural area. In fact, I will do this again at the end of summer when it's cooler, and from now on do it every spring.

If you think this sounds overboard, think of it this way. The amount of what I saw dislodged on that first go 'round was amazing, to say the least, and is detrimental to your engine and could possibly cost you ALOT of money, if you don't clean it out periodically. If the pic I posted above doesn't hit home, consider that that 10x10 inch pile, nearly 2 inches tall covers ALOT of surface. If I am doing the math correctly, imagine laying out am 8x4 ft.sheet of sand, 3/8 inch thick over the front your radiator! Do you think that could be a problem? Yikes!

 

Actually, that's not quite correct. A 160 degree thermostat ony begins to open at that temperature. In real life, at average ambient temps any thermostat will be fully open at normal operating temps, so the same coolant will pass through the radiator regardless of t-stat temp.

The advantage of a 160 t-stat is that it begins opening sooner rather than later, so your engine heats up more gradually, which is better for the metal.

On a long drive in warmer weather, your engine will heat up anyway, regardless of the t-stat temp, but it can also be helpful because it can stay cooler a bit longer, and it's easier to cool a cooler engine that one that's hot.

With that said, a 160 could be detrimental in cold weather by NOT allowing the engine to heat up quickly enough for the conditions you might be driving. For example, if you're in Minnesota in the winter and need to drive 50 miles on the freeway, your car will take that much longer to warm up and may never reach the optimal engine temps, so if you romp on the accelerator before it's within the optimal engine temp, it might not perform as well as it should, and could also be hard on the engine.

In fact, it for this very reason that one member of this forum, EvilTwin, runs a stock t-stat in the winter, and a 160 in the summer.

 

OK, this is a REALLY old thread, but the other day, with 100+ degree weather, I saw my coolant temp hit 227, after exiting the freeway. Normally, at freeway speeds I am in the mid 180s and in traffic I get up to the mid 190s. I prayed that a simple radiator-fin cleaning would do the trick, as it did when I cleaned it almost 7 years ago to the day.

Sure enough, even though this time only about 2/3 of the sand/road grime that came out 7 years ago (as depicted in post 25 above), this cleaning again fixed my problem. I am now back to normal temps.

It's a simple process, requiring only a 3/4" piece of wood to insert into the top "channel" of the radiator (for tapping on with a rubber mallet so you're not hitting the radiator directly). If you have an air compressor, you can easily make a little right-angled blow nozzle to fit over your stock blowing attachment and use that, too, if you want to blow through the fins, after the tapping. For what it's worth, I did not do any blowing the first time, just tapping, and the tapping alone worked great!

It amazes me how such a little thing can have such a drastic effect. But, I guess if asphalt concrete retains much more heat than ambient air, granules in radiator fins not only prevent air movement between the fins, the granules themselves also retain a LOT of heat.

Makes me wonder if all the people that replaced their radiators, or upgraded them to "more efficient" models wasted their time and money. After all, the angled-back orientation in which GM positioned radiators in our cars is such that granules can't fall out on their own, like they can with vertically-oriented radiators. Hence, a regular cleaning is a must, even of there are no leaves or bags. ;-)

 

I live in Louisiana, and it was kissing 102 with 100% humidity last weekend.

Sitting in some stop and go traffic, I was seeing coolant temps of 220-227 and oil temps of 240-ish.

I ended up removing the intake, and a the air bridge, and spraying a hose through the condenser core, and what I could spray through the back of the fans, to help clean some of the dirt out. It worked pretty well, I definitely recommend it.

 

The A/C condenser sits in front of the radiator and it needs cleaned also... lots of junk gets stuck between them... and the most efficient way to clean the radiator is to remove it...

Copied from a 2005 Evil Twin post

IT is a tight clearanced aluminum alloy engine. it has a sweet spot. Every tuner knows this... keeping it in the sweet spot is what everyone strived for... the sweet spot is 190/200 coolant and 200/210 oil temp.

 

Gonna try this! Thanks. MrLeadFoot, do you remove anything before you start tapping? I just got my vette recently, need to do this, but somewhat unfamiliar with it still.

 

REALLY simple, Gimp. And, you do NOT need to remove the radiator, condenser or big shroud under the air filter, either.

Not sure if you have a stock air filter or aftermarket, so instructions maybe slightly different, depending upon your particular setup.

1) Disconnect MAF sensor harness at the MAF sensor near the air filter (it's easy, just pinch the connector to release the locking tab, and pull it off). Using a small screwdriver, unfasten the clip that holds the MAF harness holder to the large condenser shroud so you can move the harness out of the way (this makes it easier to remove the radiator shroud as described in step 4 below).

2) Remove the air bridge (the plastic piece between the intake manifold and air filter assembly).

3) If you have a stock air filter assembly, remove the air filter box.

4) Remove the radiator shroud (2 bolts on each end of the shroud).

5) You can now see the top edge of the radiator, and the condenser which is still under the air filter box and large cover (don't know the technical name of this piece, so I refer to it as "large condenser shroud").

6) Place a piece of 3/4" plywood edge-wise in the channel on top of the radiator. Tap on the opposite edge of the wood. Start soft, until you get an idea of how hard to tap to effect a "jolt" to loosen the dirt from between the radiator fins, without damaging the radiator, of course (remember that it's aluminum so it's malleable, hence the wood used as a buffer between the rubber mallet and the radiator). Move the wood around if you like, and if you have a lot of crap in there, use a jack and jack stands to raise the car and tap from underneath AFTER you're done with the top. You'll see that the dirt falling out from the top portion of the radiator will fall down into the lower part, so you probably want to tap that out from the bottom. Put on some eyewear and cover your nose and mouth to prevent crap from getting in your eyes, nose and mouth (ask me how I know!).

7) [Optional] I have an air compressor that came with an attachment for blowing. It's kind of like a gun with a trigger. On the end is a long, thin, metal tube through which the air blows. I made a makeshift extension with right angle nozzle so I could stick it down between the radiator and condenser, and then again between the radiator and fans, to blow air through the radiator from both directions. I used some 1/4" drip sprinkler hose (which happened to fit perfectly over the "gun's" long air tube), and put a drip sprinkler right angle connector on the other end of the 1/4" hose to get a right angle "blower". When you stick the tube down between the radiator and condenser you don't have to hold the sprinkler hose (because they're so close together that the tube can't flap around; you'll see what I mean), but when you're blowing at the top of the radiator, you will have to hold the hose when you blow so the air pressure doesn't cause the 1/4" hose to flap around and whack you (don't ask me how I know this, too!). Note that using air just helps get out the remnants of the crap, but doesn't really loosen up sand and road grime that packs between the fins. The tapping is what actually loosens the crap and makes it fall out. In fact, the first time I did it, I did it without using the compressor, and it's been fine for 7 years; I just used the compressor this time because I have one so I can.

8) [Optional] If you did jack up the car, you might as well get under it and blow through the condenser as well.

9) [Optional] You can also pry back the big plastic shroud covering the condenser at the top and stick the nozzle down there and blow the condenser out from the top.

Note that if you don't have a way to blow air directly through the radiator and condenser fins, don't even bother with compressed air because it won't work unless you blow straight through the fins. Hope that makes sense.

Sounds like a lot of steps, but I assure you they are very small steps, and it's easy. The only part that might be SLIGHTLY puzzling is if you have a stock air filter assembly and you can't see how to remove it. It is very simple once you know how to remove it; just search for air filter box removal and I'm sure someone has already covered that.

I'd be interested in hearing your before and after coolant numbers. And, if you have the means, post a pic of what ends up falling out of your radiator, like I did in post 25 above. I bet you'd be surprised how much accumulates between the fins, and even more surprised that such small things can cause BIG heat problems.