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Coolant Mystery / temps up but no overheat


gspoth

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Guys,

I've been watching a cooling event in my 94 elso for a few weeks now. On highway speeds it always ran 203-207 with air on in warm Texas weather. Lately though, I ve' noticed that the temp moves very quickly ( more than before) up to 207 , 208 highway with air on right up to 216-223 even as high as 231/

I thought I had found the problem when I schecked the surge tank a couple of weeks ago...sure enough it was low so I added about a quart and a half of 50-50.

That seemed to taper the temps a bit but nothing like it was originally.

There are no signs of any leaks on the car....sits in a clean garage so I can monitor....up on the rack no sign of leaking. I'm wondering if this can be the beginning of a head bolt problem or something as simple as a surge tank cap not holding the right pressure.

Car runs fine , no codes, no leaks and no overheat condition.....just an increase in temp and adding a little 50-50 to the surge tank.

Has anyone seens this problem before ? Would apprecaite any thoughts on this .

George

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How is the seal around the water pump? Are your cooling fans working properly?

Here is a response I got when I though I had temp problems: got to give props to jadcock for this....

220 is just fine for your car. The cooling fans have two speeds (controlled by three relays underneath the radiator). The low speed isn't even triggered until the coolant temperature reaches 229*F. High speed is somewhere near 240*F I believe. 220*F is just barely warmed up! You want to see at least 212*F on a normal basis to burn off residual moisture in the oil from cold starts.

No worries -- your car's running fine!

Ed

--------------------

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Thanks for the info ..here's some more background and recent update.

I have changed the collant and added bars leak ( 8,000 miles ago and 1 year ago)

Both cooling fans work fine. / water pump seal area dry / water pump belt fine etc. Everytrhing visible to the eye is fine

Update - just got throuigh driving the car on a 4 hour trip.... 70-80 mph with air on, ambient temp 84-87 degrees. The temp on the car ranged from 203 - 250.

When I hit passing gear going from 70 to 85 mph and let off temp rose from 203-250 within seconds. The car has never done that before or ever reached 250....and believe me I have had it WOT on the backroads on 100 degree days but the temp never rose as fast or as high as it did today. I was pretty concerned on the quick temp rise so I killed the A/C, jacked up the heater and bled off some of the temp. This was 2 hours into my trip.....after I got it down to 203, I put the A/c back on and drove it 70-75 with temps never getting above 216.

I have had the car about 4 years now but just in the last few weeks, the temp seems to be going up and down quickly, and as a rule of thumb it is running hottter. I'm wondering if the radiator is getting clogged and may need a flush.

The only thing that I have done recently to the car that might be near the temp events . Those things were ( 1. I changed the EGR valve - would that make engine run hotter ?? )

Lastly, while I realize that the temps the car is running are within normal range, it is kinda of weird how the car just started to act up within the last few weeks. sending temps up and down...not steady and predictable like before

George

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The problem sounds like a drive belt tensioner on the water pump drive belt. Check to make sure it travels freely on its pivot (rotates back and forth). Often, this tensioner can get stuck on its pivot, and not provide sufficient tension on the drive belt. This shows up many times as "overheating" when you goose it. Lubricate the tensioner pivot and make sure the spring is providing good pressure on the tensioner. Good luck.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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update - I got up this morning to take a look under the hood and examine the water pump belt tensioner. It seemed to be fine, belt was tight , no cracks and tensioner appeared to be providing correct tension

I also pulled the cap off my surge tank to take alook and sure enough....was low on coolant again. No apparent leaks from under the car or around the engine area. I checked heater core area for dampness and it was as dry as a bone.

Looked at the dipstick to see if there was anything other than oil there.......after a few sticks to be sure...it was just oil.

The car does not smell of coolant anywhere,,,even exhausts

I'm wondering if the cooling level was low to start with and maybe just started to raise its head during summer months....the good news is that the car has never overheated.

I'm stumped.....any ideas ?

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a pressure test would be right thing to do. I have recently replaced both end radiator tanks and before taking the action wanted make sure there was no more weak links. I openned the hood and increased the RPM up to 3000-4000 and guess what - coolant fontaining from a crack in the TEE - heater valve. Since I do a lot of WOT I have been loosing coolant that way and would never know unless the hood was open.

Try and pay attention to potentialy vulnerable points - hose connections, plastic parts etc.

The saddest thing in life is wasted talent

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Maybe it's the temp sensor. It is 10 years old.

2001 STS Mettalic Otter Grey, Black Leather, 213,000 kilometers - miles - ? Still running strong!

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Maybe it's the temp sensor. It is 10 years old.

Exactly my thought, either a temp sensor or a thermostat is starting to go.

But then again, it still leaves the mystery of where the antifreeze is going. If he's not seeing any smoke from the exhaust and he's not finding anything in the oil, where is it going? Unless the system is just so empty that it's got a huge air pocket somewhere and needs to be refilled again?

The surge tank is empty or low, but what's the level in the radiator? Is it covering the top of the fins? Is the radiator fluid circulating rapidly when the engine is hot?

Additional: Are you SURE you're not losing the fluid while you're driving? Do you find any evidence of wetness inside the engine compartment?

If you really want to make people safe drivers again then simply remove all the safety features from cars. No more seat belts, ABS brakes, traction control, air bags or stability control. No more anything. You'll see how quickly people will slow down and once again learn to drive like "normal" humans.

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I think adallak and Marika might have the idea. Since your garage floor is dry and everything else checks out fine then I would think one of two things: 1) Your leaking coolant under load, probably through a hose or joint that has a clear shot to the road below. That would account for no coolant in the engine compartment. 2) Your adding too much coolant and when you drive the car heats up and dumps the "extra" coolant out the overflow hose.

Which raises the question: Why did GM make the reservoir tank black instead of clear? I'm sure there is a valid reason......right? Everytime I look at it I just shake my head in disgust.

-kg

"Burns" rubber

" I've never considered myself to be all that conservative, but it seems the more liberal some people get the more conservative I become. "

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UPdate - I think the thermostat was the problem..read below

Guys, here is the latest. I took the car to my friendly radiator shop and had them do the following

Pressure check - ok held well

Removed Radiator and cleaned ( guy at radiator shop said the radiator wasn't clogged)

Replaced pressure cap

Replaced thermostat

Results were excellent ..Car temp held at 198-205 range during 4 hour raod trip last night. I drove the car 70-75-80 with A/C and the temp stayed low and solid 198-205.

I am beginning to believe that the tenmp variation was due to the thermostat going bad.

On the loss of coolant, I will be watching this over the next few days to see if there is any variation. New coolant was added at the radiator shop along with GM supplement. I'll keep you posted

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I was going to say thermostat however one of your symptoms was loss of coolant or having to add coolant which confused the diagnosis.....it certainly seemed to be the water pump belt/tensioner for awhile also.. Let us know about your coolant levels. Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Well, not trying to alarm you, I had the exact same symptoms.

- Loss of coolant.

- Overheating on hard acceleration.

- Temperature fine with regular driving.

I checked the following:

- Thermostat replaced.

- Coolant changed.

- WP belt/tensioner checked.

- No coolant smell in exhaust.

- No coolant in oil.

- Fans operating correctly.

- Water pump fine.

I finally did a comoressed air test on all cylinders.

Compressed air test = Position each cyl at top dead center on the compression stroke and add 120 psi air thru the spark plug hole. (requires an adapter)

With the rad cap removed, listen very carefully in the surge tank.

In one cyl, #5, I could hear bubbles of air.

I immediately had that sick, "oh no" feeling.

It was a bad head gasket. Well actually, it was a pulled head bolt. The increased pressure of wide open throttle, would "lift" the head at the pulled head bolt and allow exhaust to enter the cooling system and cause a rapid overheating.

Also, there is a test that a shop can do, they can check for exhaust (CO) in the coolant. I didn't have this done since I had bubbles with compressed air.

I hope this is not your problem and you find a less complex (costly) cause.

Barry

2008 STS V8
2016 Colorado Z71
1970 Corvette LT-1 Coupe

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Barry, thanks for the info. I forgot to add that on my 4 hr drive last night going between 70-80 I had a few WOT's to test the temp. The temp never got above 205 even with the WOT. That was with the air on and ambient temp at 80-81 degrees.

I am hoping it's not the head bolt/s gasket. I am now watching the surge tank as I seem to have the temp problem under control

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Hello. I live in Chicago and recently made a trip to New York. When I left Chicago, my coolant temp was running around 199-205 just like gspoth, after arriving New York, my temp starting rising troughout the days. Temp was up to 130's. On my way back to Chicago temp got even hotter. The coolant went all the way up to 150. There is no coolant loss. Which brings me to believe that it might be the thermostat. Does anyone know at what temp does the engine overheats and shuts off???

Caddyjag

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Do you mean 230s and 250? It depends on when you saw those temps, in traffic the 230 is ok. The 250 seems high. When are you getting these temps? Make sure your cooling fans are coming on first and check your water pump belt for slipping and that the tensioner is not binding and as a result not providing proper tension. How is the coolant level? I think but I am not sure that you will get a warning at 265 and the AC will shut off.

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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sorry. Yes I did mean 230's and 250. I did not have the A/C on. In the highway going 70's the temp read from 234-244 and then I aproached the toll booth which was congested. I got stuck there for a good 15 minutes barely moving. Temp went up to 252.

Caddyjag

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sorry. Yes I did mean 230's and 250. I did not have the A/C on. In the highway going 70's the temp read from 234-244 and then I aproached the toll booth which was congested. I got stuck there for a good 15 minutes barely moving. Temp went up to 252.

Caddyjag

Wowie, along with your blood pressure... I am on Long Island so I know the traffic you are experiencing. Make sure cooling fans are coming on. Your thermostat could be binding and sticking partially open, I would change it first if the cooling fans are coming on, I assume you checked the coolant level. Also look at the water pump belt and belt tensioner to see if the belt is tight and not slipping. What is the condition of the belt, you know its on the drivers side of the car it is driven by a belt off the cam shaft. Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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Update - I am feeling more confident by the minute that I had a bad thermostat. Today in 90-92 degree temps, did a lot of stop and go driving and also idled car with the air on for 25-30 minutes...tenp reached 223. which is the old normal temp.

Tomorrow morning. I'll check the surge tank and report coolant level.

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Update - I am feeling more confident by the minute that I had a bad thermostat. Today in 90-92 degree temps, did a lot of stop and go driving and also idled car with the air on for 25-30 minutes...tenp reached 223. which is the old normal temp.

here is an easy thermostat test you can run withoyt leaving the car:

1. In the morning start the car and let it idle while watching the coolant temp at your DIC (my Seville 1991 gives that opportunity)

2. At some point (201 degrees in my point) the temp. will drastically drop say to 170 and then continue to grow. This drop indicated the point the thermostat opens ( a little bit higher than actual of course).

The saddest thing in life is wasted talent

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Update - I am feeling more confident by the minute that I had a bad thermostat. Today in 90-92 degree temps, did a lot of stop and go driving and also idled car with the air on for 25-30 minutes...tenp reached 223. which is the old normal temp.

Tomorrow morning. I'll check the surge tank and report coolant level.

Terrific! I am going to change mine soon also.... Mike

Early on sailors navigated by the stars at night and the North star became the symbol for finding ones way home. Once you know where the Northstar is you can point your ship in the right direction to get home. So the star became a symbol for finding ones way home or more symbolically even finding ones path in life.

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2. At some point (201 degrees in my point) the temp. will drastically drop say to 170 and then continue to grow. This drop indicated the point the thermostat opens ( a little bit higher than actual of course).

The behaviour you describe is typical of an outlet thermostat cooling system. If the engine is under load, there may be a significant upwards temperature excursion observed (220+ F depending on the sensor location) prior to the thermostat opening fully. The Northstar has an inlet thermostat, which regulates the flow of cool coolant into the engine. This avoids the thermal shock associated with outlet thermostats.

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