Well,

I think I've finally figured out the source of my overheating.

I noticed when inspecting the cooling fans that the upper radiator hose was warped, and one part of it had melted because it was coming in contact with the lower engine block. I had that hose immediately replaced, and I confirmed that the cooling fans are working. The engine coolant has recently been drained and filled, yet the gauge in the car still says the engine is running too hot.

Well, I just replaced the hose and I notice it AGAIN is coming in contact with the lower engine block, though not while the engine is idle. I've got to figure the motor mounts are shot, and that's what's causing the radiator hose to come in contact with the block. This naturally raises the temperature of the coolant which leads to a host of other problems.

Can anyone verify that this makes sense? Anyone throw me what a motor mount job should cost? Thanks,

The car is an 01 Deville DHS with 89000 miles

no, it doesnt make sense. a hose just touching the block cannot overheat engine.
if it is kinked .. maybe.

at any case, i be doing something to protect the hose from rubbing on anything.
that would not be a healthy condition as it will eventually fail and blow.

the block is not going to be any hotter than the cylinders where the coolant does
its job. that cannot be it.

the only thing hotter than the engine are the exhaust manifolds / headers.
but if your hose touches that, you got bigger problems and fast. it is called melting rubber.

the mounts may be shot but that would be it - if at all.

Stealth,

then at this point, do you know what it could possibly be? Both coolant fans are working, the radiator is not leaking coolant, the air conditioner blows ice cold, the heater works appropriately, the coolant's been drained and filled and given stop leak, there are no puddles on the ground and I'm not losing any coolant from the overflow.

There is no smoke coming from the engine and it's never actually overheated, but it is definitely running hot. In yesterday's mid 90 degree weather after about an hour of stop and go traffic, the car was running very sluggishly, as if it were running on four cylinders.

Who knows, maybe the head gasket is already blown. But again, it doesn't show the symptoms of that. Maybe the water pump? But I'm not noticing puddles on the ground, or a loss of coolant. I'm really at a loss for this one, but I do know it's overheating, and this problem may have been happening for some time now.

assuming all else is good .. oil level, no exhaust leaks, good 50/50 coolant mix,
proper rpms for speed,


things that come to mind?
- a sensor giving wrong readings,
- a stat not fully opening or isntalled backwards
- a radiator internal blockage
- a cat / mufler blockage
- an air restriction ahead of the radiator (bugs)
- cavitation in pump - air in system
- collapse of lower hose at high speed

check the FAQ for others ...

i'm sure you said it somewhere, but when does it run hotter than you like?
conditions, speed, ambient, fuel type, pinging, erratic power, etc ..

codes?
writ it all down in this thread and then PM the TECHs with the
link for this thread .. hopefull they arent all busy on this Sat.

gotta run .. recital day for my kid

Whenever it's any type of stop and go traffic, the needle climbs. As soon as the traffic breaks and I get up to a consistent speed the needle goes back to the middle. The problem is worse when idling, and worst on very hot days when idling. I realize now that yesterday, when it felt like my car had no power, it was because it was running in "vehicle protection mode."

I use premium fuel and I hear no engine pinging. There are no visible leaks under the car of any kind, except for water from the AC compressor. I am not losing coolant, nor is it "bubbling" or overflowing when the surge cap is removed and the engine is running. The cooling fans run when idling and when the air conditioner is being used.

Because the upper radiator hose was melting, I am pretty sure there is an issue with overheating, and it's not just a matter of faulty sensors. The upper radiator hose gets extremely hot, so I'm thinking it's not the thermostat; I was told that is one way to tell (could be wrong.) There are no major restrictions in front of the radiator; some insects, but nothing that would do this.

I can't rule out a radiator blockage, a cat/muffler blockage, cavitation in pump, or a collapse of the lower hose at high speed.

Given the mileage and the year (01 DHS 89000 miles) I'm thinking it could be an issue with the water pump? Though, there is absolutely no leakage or loss of coolant that would be consistent with that.

If not the water pump, I fear it's the head gasket or the head bolts. If it's either of these issues I'm in dire straights.

ORIGINAL: JP500

Whenever it's any type of stop and go traffic, the needle climbs. As soon as the traffic breaks and I get up to a consistent speed the needle goes back to the middle. The problem is worse when idling, and worst on very hot days when idling. I realize now that yesterday, when it felt like my car had no power, it was because it was running in "vehicle protection mode."

I use premium fuel and I hear no engine pinging. There are no visible leaks under the car of any kind, except for water from the AC compressor. I am not losing coolant, nor is it "bubbling" or overflowing when the surge cap is removed and the engine is running. The cooling fans run when idling and when the air conditioner is being used.

Because the upper radiator hose was melting, I am pretty sure there is an issue with overheating, and it's not just a matter of faulty sensors. The upper radiator hose gets extremely hot, so I'm thinking it's not the thermostat; I was told that is one way to tell (could be wrong.) There are no major restrictions in front of the radiator; some insects, but nothing that would do this.

I can't rule out a radiator blockage, a cat/muffler blockage, cavitation in pump, or a collapse of the lower hose at high speed.

Given the mileage and the year (01 DHS 89000 miles) I'm thinking it could be an issue with the water pump? Though, there is absolutely no leakage or loss of coolant that would be consistent with that.

If not the water pump, I fear it's the head gasket or the head bolts. If it's either of these issues I'm in dire straights.




i'm leaning heavily on your description of the problem. so here it goes.
assuming the car has a history of good coolant system maint, not gunked up or oxidized and scaled inside ..

- if the head gasket was leaking gas into the coolant, you be having worst problems at high speeds than low speeds.
when the pressures are really high, the gases blow by the head gasket faster if they have failed. however, peace of
mind is cheap. testing for exhaust gas is easy and cheap. take a look in the FAQ section.

- if the TOP hose is much hotter than the BOTTOM hose, that to me points to a blockage in radiator.
you should expect the bottom hose to be cooler, by a little bit, not by a lot.


Whenever it's any type of stop and go traffic, the needle climbs. As soon as the traffic breaks and
I get up to a consistent speed the needle goes back to the middle.


to me, this points out to not enough coolant circulation, not head gaskets. anything is possible, but this is unlikely.

sticky Stat?
rad blockage?
air in system? did you open the relief valve under the beauty cover and let any air out?

probably no cat/muffler blockage by your description.

i am not much of a believer in flushing radiators, they are cheap and last 10 to 20 years
if maintained properly. it is your car, your $$$ .. but if that was my car, i be dropping
a new rad, new stat, new belt. The $300 you spend is less than a mechanic visit.

water pump impellers .. can they get loose from the shaft? havent a clue on your design.

now, here is a kicker .. you didnt say when this started .. or how long you had this car.
i'm going to get a few snickers for this - but .. what the hell ..
i have seen several reports of impellers installed backwards by the mfg companies.
some of those cars got away with that until something else decreased cooling efficiency
and there the pump issue surfaced. may be rare, but it is out there.

Thank you for the detailed response. I really appreciate all the time you've put toward this.

I'm not sure about my car's coolant maintenance. It has recently been drained and filled, and it took 3 gallons (1.5 of distilled water, 1.5 of dexcool) of fluid. I asked the tech who did the job whether it was gunky or extremely dirty and he said it wasn't. I don't see anything gunky in the overflow. I know that's not the best indicator but it's something.

You seem to be leaning more towards an issue with blockage/ thermostat/ air in system, than the water pump. Is there a reason you're leaning away from the pump? Considering the age and the mileage, and that the pump is responsible for flowing the coolant, it seemed to me that the pump was a likely suspect. But, there is no leakage, unless it's mixing with the water from the air compressor and I can't tell. Unlikely though, because I don't see any oil deposits on the ground.

I will follow your advice with the radiator if that is indeed the culprit.

If you could tell me a bit more about why you're moving away from the water pump, that would be very helpful.

Thanks,

Joe

ORIGINAL: JP500

Thank you for the detailed response. I really appreciate all the time you've put toward this.

I'm not sure about my car's coolant maintenance. It has recently been drained and filled, and it took 3 gallons (1.5 of distilled water, 1.5 of dexcool) of fluid. I asked the tech who did the job whether it was gunky or extremely dirty and he said it wasn't. I don't see anything gunky in the overflow. I know that's not the best indicator but it's something.

You seem to be leaning more towards an issue with blockage/ thermostat/ air in system, than the water pump. Is there a reason you're leaning away from the pump? Considering the age and the mileage, and that the pump is responsible for flowing the coolant, it seemed to me that the pump was a likely suspect. But, there is no leakage, unless it's mixing with the water from the air compressor and I can't tell. Unlikely though, because I don't see any oil deposits on the ground.

I will follow your advice with the radiator if that is indeed the culprit.

If you could tell me a bit more about why you're moving away from the water pump, that would be very helpful.

Thanks,

Joe




mostly, coolant pumps fail in one of these modes..
- bearings -- noisy, you can hear it.
- seals - leakage, you can see it.
- impeller gets loose at the shaft .. that one is a little harder to check

the pumps, are impeller pumps, that simply dont wear out unless you ran sand, grit, or metal flakes in the coolant.
however, the chance of the backwards impeller .. well, it does happen.

the radiator flow ducts, are small and can block one by one until too many are no longer allowing
coolant to flow. if you got a infra-red thermometer, you could check each duct to see if some are blocked.
flushing often does not open all the ducts and you cannot tell if they did. that takes me away from those methods ..
i kind of like a 100% efficient working radiator.

remember, all along, i went by YOUR DESCRIPTION of the problem, the when, the how ..
if any of that is incorrect, all bets are off .. that is why mechanics test drive them - to see for themselves.







.

Thanks Stealth.

We'll find out this week. At least I know what to tell the tech.

ORIGINAL: JP500

Well, I took the 01 DHS with 89000 miles to the dealer today for a diagnosis.

They ran a pressure check and found that the head gasket was ok (big relief.)

They checked the cooling fans (ok) they checked that the lower hose was cooler than the upper hose (radiator doing its job.)

They drove it around town and recorded the temperature, which they said was around 220-225 in light traffic. Personally I think that's too high, but they seemed to disagree. Considering it wasn't extremely hot today and that the traffic count was light, I tend to think this is too high, but that's my opinion.

Ultimately, they diagnosed it saying it was ok, and they looked at me like I was crazy for saying the car was overheating. I even showed them when I arrived that the temperature needle was above the halfway mark. They seem to think the gauge is bad.

You have to understand how frustrating this is from my end. This took two hours and $65 to diagnose, and a part of me is thankful that I found a dealership honest enough to tell me there isn't a problem, but the other part of me is still convinced something is wrong. The needle climbs above the halfway mark while driving. Performance seems to suffer the longer I drive. Everything I've read here tells me that a temp of 225 on a not-so-hot day is too high. A few days ago it was over 100 here and during traffic I had a huge drop-off of power. Although no messages came up, I'm convinced I was running in protection mode, because it felt like the car was practically going to stall out, and I couldn't seem to get it above 50 MPH no matter how hard I pressed the pedal.

I just don't know what to do at this point. I've had two different mechanics tell me it's A-OK -- one of whom was a caddy dealer. At this point I think the only thing it COULD be is the impeller installed backwards or the thermostat installed backwards, but how the hell can I tell without having them rip the engine apart and charge me lots of money.

I'd like any advice on what to do from here. Also, I just had the top radiator hose replaced, so I assume that if the thermostat was installed backwards before they would have noted and installed it properly this time around.

I'm almost out of ideas here. I'd appreciate anything you guys can suggest.

Thanks,
Joe



maybe it is okay .. maybe the sensor is off a bit.
mechanics dont turn away work if at all possible.
that is a clue right there.

did the sensor agree with the temps he got?

did the sensor agree with the temps he got?

Not sure. He hooked up some thermometer seemingly underneath the dash as he was driving it. He mentioned the needle went above the 50/50 mark while he was driving, but never beyond a certain point. He only drove it for so long, however.

I agree with you that a tech would never turn away work. That is part of the reason I'm relieved. And I guess they're a pretty honest dealership there... a rarity in this day. Also, pretty reasonable for a diagnosis at $65. If you're looking for a good Caddy dealership (in terms of service) in the Boston area then private message me and I'll release the name.

In a car that's notorious for head gasket issues, it's very unsettling to sit in rush hour traffic on a 100 degree day with the Air Conditioner blasting as your temperature gauge is too high. I'm thankful because the warmest days of the year are behind us in the Northeast.

For now I guess I'm going to hold off on doing anything else.

Stealth, et all, thanks for all your help. Hope to learn more from this site.

ORIGINAL: JP500

did the sensor agree with the temps he got?

Not sure. He hooked up some thermometer seemingly underneath the dash as he was driving it. He mentioned the needle went above the 50/50 mark while he was driving, but never beyond a certain point. He only drove it for so long, however.

I agree with you that a tech would never turn away work. That is part of the reason I'm relieved. And I guess they're a pretty honest dealership there... a rarity in this day. Also, pretty reasonable for a diagnosis at $65. If you're looking for a good Caddy dealership (in terms of service) in the Boston area then private message me and I'll release the name.

In a car that's notorious for head gasket issues, it's very unsettling to sit in rush hour traffic on a 100 degree day with the Air Conditioner blasting as your temperature gauge is too high. I'm thankful because the warmest days of the year are behind us in the Northeast.

For now I guess I'm going to hold off on doing anything else.

Stealth, et all, thanks for all your help. Hope to learn more from this site.




i be going back and asking the teck about the temps. it will give you some satisfaction and
he will give them to you if he wrote them down or remembers.

Advice? IF you havent changed the coolant, do it asap.
then, never let it get older than 24 months. the headgasket issue is a combiantion of
old coolant, overheating, loss of fluid. It almost requires all three to make that happen.

as far as the Cadillac dealer .. feel FREE to post it, including the name of the TECH.
We dont mind posting such good people as that helps other members.
You wont get any grief from us here.

My Cadillac sits on the gauge at center, but i have seen it beyond center now and then.
I usually hear the fans kick on and the gauge move back to center.
however,
On of my non-Cadillac trucks, this works a bit different. the gauge sits about 1/4 of the way
except on a very hot day in slow traffic or running up a mountain. I have seen that gauge climb to
3/4 up more than once, i have had to shut down the A/C and a few times i even turn on
the heater to take more heat away. Moral of the story is that sometimes, the engine is comamnded to
put out more heat than normal.

gauge could be bad

He said the temp was in the 220s. I asked him if that was too hot (rhetorically) He said no. Coolant has been changed as of this july, and I gave it the tablets too.

The dealership was Olsen Cadillac in Woburn Mass. They were half the price of other dealers on the diagnosis fee and, as stated, they didn't try to charge me for work that didn't need to be done.

Hello Stealth,
Has anyone checked the water-pump belt? Maybe it is slipping.
I recently moved to Charlotte North Carolina and the temperature has been over 100 degrees most days and my 96 STS runs terribly in the heat.
The Power drops off, but not as much as yours, The Temperature guage does swing one or sometimes two marks past the half way mark, but not into the red, and I have a bad case of Spark Knock which mostly goes away at night when the outside temperature is less than 90 degrees.

So I would check the belt and then you have pretty much covered everything I can think of.
I am considering to remove my thermostat and wire the cooling fans to run whenever the engine is running. I have checked a couple places and there are not any oversize radiator for my car readily available.

When I bought the 96 STScar about five years ago, the thermostat was missing. It took a couple years for me to discover that there was not a thermostat in the car. I did install one and the car warms up faster and the heater works better during the winter.

Jon

ORIGINAL: jonrodman

Hello Stealth,

Has anyone checked the water-pump belt? Maybe it is slipping.
I recently moved to Charlotte North Carolina and the temperature has been over 100 degrees most days and my 96 STS runs terribly in the heat.
The Power drops off, but not as much as yours, The Temperature guage does swing one or sometimes two marks past the half way mark, but not into the red, and I have a bad case of Spark Knock which mostly goes away at night when the outside temperature is less than 90 degrees.

So I would check the belt and then you have pretty much covered everything I can think of.
I am considering to remove my thermostat and wire the cooling fans to run whenever the engine is running. I have checked a couple places and there are not any oversize radiator for my car readily available.

When I bought the 96 STScar about five years ago, the thermostat was missing. It took a couple years for me to discover that there was not a thermostat in the car. I did install one and the car warms up faster and the heater works better during the winter.

Jon


i assume the mechanic took a look at the belts.

as for your engine, better check your timing. unless you have heavy carbon deposits, it shouldnt do that.

I assume they checked the belts, too. I wouldn't know the sound a bad belt makes but I'm pretty sure a mechanic would. And there's no leakage, so I think we're ok all around.

I did run the on board computer and I found a few codes. But like an idiot, I accidentally erased them after a run through. I'll wait and see which come back on, if any, and report in.

On that note, what does it mean when they say "ALL ID" when running the test?

ORIGINAL: JP500



On that note, what does it mean when they say "ALL ID" when running the test?



who is they ?

when you run the vehicle's onboard computer and you have the choice of running "ALL Codes" or "All ID"

ORIGINAL: JP500

when you run the vehicle's onboard computer and you have the choice of running "ALL Codes" or "All ID"

ORIGINAL: _X_CaddyTech

the ALL ID is an option to show you the ID numbers off all the modules installed in the vehicle. it is sometimes needed when talking to GM Tech assitance at a dealership. You wont decipher them as they are for the factory to identify what software and hardware are in a specific controller in case there is a problem that another newer module with newer harware or software.

Thanks. Scoured the whole web and no one had an answer for that one.

ORIGINAL: JP500

Thanks. Scoured the whole web and no one had an answer for that one.


like we say,
there are REAL Techs here ..

glad he had the answer for you.

ORIGINAL: JP500

[In a car that's notorious for head gasket issues, it's very unsettling to sit in rush hour traffic on a 100 degree day with the Air Conditioner blasting as your temperature gauge is too high. I'm thankful because the warmest days of the year are behind us in the Northeast.

For now I guess I'm going to hold off on doing anything else.



Just came across this series of posts. First I don't think an 01 Northstar is notorious for head gasket issues. Early engines maybe but not 01, especially when proper maintenace is done on the cooling system.
I agree that 220 degree readings are ok because the protection mode kicks in at 248 degrees. The fact that the protection mode did kick in points to a problem however. Northstar water pumps are not like a conventional water pump on say a Chevy small block and I have seen them gobad and barely show any signs of leakage or fault. The pump is on the drivers side of the engine not on the passenger side with all of the driven accessories so even if you were looking for a leak you probably are looking in the wrong place.

I suspect the water pump is either bad or going bad based on everything posted here.

Hello Jp500 any updates on the overheating problem u r having??? I have 97 deville 95k and i am having similiar problems when i am sitting in traffic on my way to work. I also like in the boston area so i am in traffic everyday going to work. My caddy will creep up to about 226 degree then will kick back down to 217 and then go to 205 and stay for alittle bit then jump back up slowly by 4to5 degree each time. Wondering if my fans are not moving as fast as they should on something wrong with what ever sensor or sensors call the fans to engage and at what degree. please advise with any news. Yeah and Olsen Cadillac is very awesome!!!!! When i purchased my 97 deville 1 yr ago i took it to them to look everything over and they were sooooooo helpful and polite. I also got 3 phone calls and a letter asking if their service was good or not. Very pleased

Havea read of this link.

http://www.cadillacforum.com/m_12400/tm.htm (http://www.cadillacforum.com/m_12400/tm.htm)

Just to reply, everything's running ok in my car now.

Thankfully the weather has cooled off considerably. After olsen diagnosed the car I pretty much stopped worrying about it. I ran all the codes and nothing major came up. I really can't say for certain whether engine protection mode ever came on; I just noticed a substantial reduction in power as though the car were running on four cylinders.