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06 DTS Performance
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Discussion Starter #1
My 06 DTS is still getting hot. This time it's on the highway after about 10 minutes. It cools down immediately when I exit the highway and the fans come on.

I changed the water pump and all gaskets myself. Changed thermostat and the water pump belt with the tensioner. I have enough coolant.

There is good flow from the purge line. After I turned the car off I could hear a hissing noise from the radiator cap.

Do you think the cap is bad? Letting air in to the system somehow? Maybe the thermostat isn't good?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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The thermostat is most probably perfectly OK. The pressure cap is OK - Given that the surge tank and system is pressurized to 18 psi with the engine running, the cap cannot "let air in". The only time the cap lets air into the surge tank is if, as the coolant/engine cools down, the coolant contracts normally and air pressure in the surge tank falls below atmospheric - the pressure cap has a vacuum relief, too - to prevent collapsed hoses from just that sort of normal cooling process.

Time to head to a large parts store and borrow a cylinder block exhaust gas test set, buy the fluid, and follow the instructions. Follow the instructions - do NOT try to make it better by extended bubble times or extra fluid. If ANY coolant gets into the tester, wash it in clean water and start over - you sample the airspace over the coolant in the surge tank, not the coolant itself. If you want to see what a gas test failure looks like, idle the engine and sample the tailpipe gases.

or .................... http://www.sjdiscounttools.com/lis75500.html
 

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06 DTS Performance
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Discussion Starter #3
I have the coolant tester I just need to get some more of the liquid. I did not think it would be a problem on this 06 DTS lord please do not let it be.

But I have replaced just about everything in the cooling system except for the radiator. It is the original one and looks pretty beat up. I'm definitely going to test the head gasket now because I am just too worried.

I've saved up money for the past 2 years to buy a newer DTS not just because of the looks but everyone says the head gasket problem is finally solved so I felt more confident in purchasing one.

Now if it is the head gasket on this model.... where do I start from there?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Buy another one or repair your present engine.

Whether we like it or not, ANY internal combustion engine with head gaskets is subject to failure. I special ordered a '65 Chevelle SS 327/350 and it came from the factory with a coolant leak into #3 - not fun, but repaired quickly under warranty. The pitiful slug small V-8 engine in the 1980 Ford Mustang was noted for intake manifold coolant leaks. Mine did.
 

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06 DTS Performance
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273 Posts
Discussion Starter #5
The engine has already been replaced once in the car. It would be going on its 3rd engine or major repair in not even 10 years.

I'm going to go get the block test liquid. I'm a be praying that it doesn't change color.
 

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06 DTS Performance
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Discussion Starter #7
GOOD news. The liquid stayed blue the entire time. And my coolant level is just fine I haven't been losing any so I guess I can rule out the head gasket.

As I said my radiator looks pretty busted up I'm going to order one as well as a new reservoir cap. Everything coolant wise will be replaced and checked.

If it still gets hot after this, I'll be at a loss of words.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Do you speak "coolant purge line" and "water crossover hollow bolt/nipple" ?

If so, have you done an idle test for proper purge line flow ?
 

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06 DTS Performance
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Discussion Starter #9
Yes I have good flow from the purge line. I made sure it was clear when I did the water pump job.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Damn - there goes my ace in the hole.............

During these highway overheats - plenty of hot air from the HVAC ? (I'm fishing for coolant circulation - or lack thereof, caused by air/gas bubbles)
 

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2009 DTS
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If your radiator is "beat up" I would replace it. On the highway your engine is at a somewhat constant speed that is also higher in the rpm range than it is around town. The pump is also at a higher speed moving coolant through the radiator faster and therefore having less time to remove heat. If the "beat up" radiator isn't allowing enough airflow from collapsed fins then that's your problem. You can get a coil fin comb and try to straighten out any bent fins to allow more airflow as a test to see if it makes a difference. Another issue with a beat up radiator could be a blockage inside that's only letting the coolant through half of the radiator. Have you touched the radiator to see if it's the same temp top to bottom and side to side. Good luck and hope you get it resolved soon
Jeff
 

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2006 DTS LUX III, 2006 DTS w/sunroof & navigation (scrapped), 1997 ETC (Sold)
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To add to the above,

As I think about your statement regarding this being the third engine in that car I wonder what failed on the first two???

If one of them was a head gasket failure the odds are quite high that some stop leak could have been dumped in and the radiator core is partially plugged??

Just a thought.....and as mentioned above use a thermal heat gun to see what the temps are top, middle and bottom.
 

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06 DTS Performance
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Discussion Starter #14
I just wanted to give a update.

I bought a new radiator and lower hose radiator hose. The same exact problem occurs. The old radiator was leaking but it still did not fix my problem.

I'm beginning to wonder if I really do have a head gasket problem or not. Even though the coolant test showed good the way the car is acting during high acceleration seems like a bad gasket.

The strange thing is it cools down immediately when letting off the gas pedal or coming to a stop.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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and as mentioned above use a thermal heat gun to see what the temps are top, middle and bottom.
These are crossflow (not downflow) radiators so you "shoot" the passenger side tank, the center area of the radiator/coolant tubes (NOT the A/C condenser) and the driver's side tank.
 

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06 DTS Performance
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Discussion Starter #16
Does anyone else have any inputs? I have replaced just about every darn thing in the cooling system and it still wants to run hot on the highway. It is sitting pretty in the garage more than on the highway actually going somewhere just like every other Cadillac i have owned. They have become a laughing stock to my friends and neighbors pretty sad actually.
 

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2009 DTS
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How have you been bleeding the system? if there is an air pocket trapped in there from not fulling bleeding it can cause some funny cooling issue's. I haven't bleed a cooling system since the radiator caps were on the radiator. A lot of cars in the 90's had the caps lower than the highest point in the system and you would have to lift the front of the car up to make the cap the highest point to be able to get all the air out. I think it was the J-body cars that had bleeder screws to get all the air out also, as raising the front still couldn't get all the air with the plumbing nightmare they had. This is just a thought and could be way off as I have no idea how to bleed one of these yet. Good luck
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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No "bleeder" taps or screws. The entire cooling system, including surge tank, is now fully pressurized on many vehicles. The purge line, on a properly operating system, takes care of any "bleeding" necessary.

Study the entire Cadillac Technical Archive (Northstar engine) way up ^^^ in the top black bar as well as pertinent stickies in Engines; Northstar.
 

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2006 DTS
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How about the a/c condenser that sits in front of the radiator? is it clogged with debris or the fins bent? Both cooling fans working?
 
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