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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,421 Posts
If you run with heat on full is there any change? Are coolant Fans ever turning off ?
Immaterial - the heater core is full flow at all times. Cabin temp is varied by blending hot and cold air.

He says his fans are OK.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
So, if I want to hook my air to the cylinder, it wont work at BDC on either stroke?
Wait a minute. Are you trying to do a compression test or a leak down test? Two very different tests.

When doing a compression test, you remove ALL 8 plugs and screw the tester into one cylinder at a time. Then crank the motor over 3, 4 or 5 times to get the compression reading. The gauge will hold at the highest reading until you release the air. Then you compare all the readings to see if one is very much lower than the rest.


When doing a leak down test, you screw the tester into the cylinders (one at a time), with each cylinder at TDC compression stroke, and then pump it up to about 100 psi and see if it holds compressed air.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,251 Posts
Wait a minute. Are you trying to do a compression test or a leak down test? Two very different tests.

When doing a compression test, you remove ALL 8 plugs and screw the tester into one cylinder at a time. Then crank the motor over 3, 4 or 5 times to get the compression reading. The gauge will hold at the highest reading until you release the air. Then you compare all the readings to see if one is very much lower than the rest.


When doing a leak down test, you screw the tester into the cylinders (one at a time), with each cylinder at TDC compression stroke, and then pump it up to about 100 psi and see if it holds compressed air.
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he is simply attaching compressed air to the cylinder and looking for bubbles in the surge tank -
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
Ahhh, long thread. I forgot about that, but it might take a while with the air hose connected to get that air to the surge tank. I would think if it is a HG problem, a block test would be quicker, easier and more accurate. Wouldn't you agree?
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,251 Posts
Ahhh, long thread. I forgot about that, but it might take a while with the air hose connected to get that air to the surge tank. I would think if it is a HG problem, a block test would be quicker, easier and more accurate. Wouldn't you agree?
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YES - I agree 100% -

as I posted above -
IF the PURGE LINE is open and coolant IS flowing through it -
the BLOCK TEST is 99.9999% accurate -
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
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280 Posts
Discussion Starter #66
I already did the block test. Was negative. Tried several times, even after it overheated past 230. Thanks for the video links, Ranger. Yea, I was trying to do both, a compression test, and a leak down too, but I think my tester is leaking.
 

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Registered
1998 Cadillac Eldorado ETC
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202 Posts
Hey guys! My old high mileage 250k+ Eldo keeps overheating, right on into 230+, just idleing, or driving. Uses no coolant. Passed the expansion tank blue liquid test. Liquid never changed. Still pretty blue, even after 10 minutes of testing, after engine had just been over 230. Took out almost new radiator and cleaned it. It was good. Drained block. Removed thermostat and flushed block till clear, then put Blue Devil cleaner in. Been in for 4 days now, starting and letting warm up to 230 a couple times a day, no change. Only thing else I can think to do, is put the compression tester on each cylinder and see if its blowing any bubbles. I still think it's the head gaskets, but it's not using any coolant at all, the exhaust ends look great and it passed the blue liquid test! Anybody have any other ideas? Hate to give up on the old girl. Still runs good. Thanks for any replies!

I didn't see it in your post but...........

have you checked your cooling fan clutch? Over time, and you have plenty of miles to do this, the clutch wears out and the fan wont spin at the right speed or not turn at all. That would heat up your engine temps.
I have had to replace them on other vehicles and it makes a difference.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
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280 Posts
Discussion Starter #68
Thanks, but, it's got electric fans, and they are working. The guys set me straight on how I was doing my compression test wrong. Am gonna do it right, as soon as the weather cooperates a little. Been raining for days here, now cold and windy. Maybe this weekend I'll get to finally confirm a leaking headgasket(s), or not.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,421 Posts
.........have you checked your cooling fan clutch?
His 1995 (and your 1998) do not have fan clutches. The 2 fans are electric and operate together - with no A/C compressor function set the fans go to SLOW at 224 degrees and to FAST at 236. They normally don't run at over 30 mph - not needed. If you set A/C or DEFROST then they run in SLOW all the time to insure airflow through the condenser in front of the radiator.

Post #56 is your pre-2000 fan control circuit. You might want to read the entire thread for background.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,251 Posts
Thanks, but, it's got electric fans, and they are working. The guys set me straight on how I was doing my compression test wrong. Am gonna do it right, as soon as the weather cooperates a little. Been raining for days here, now cold and windy. Maybe this weekend I'll get to finally confirm a leaking headgasket(s), or not.
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Maybe this weekend I'll get to finally confirm a leaking headgasket(s), or not.
one last time -
IF the purge line is open and has a constant flow of coolant into the serge tank -
and IF you did the block test CORRECTLY -
and IF the color of blue fluid did NOT change at all -
you DO NOT have failed head gaskets -
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
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280 Posts
Discussion Starter #71
Yea, I know, but I've checked out every possible other thing that it could be, and it's none of them. And it has all the symptoms of blown headgasket(s). Comp test will confirm it, for sure.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,251 Posts
Yea, I know, but I've checked out every possible other thing that it could be, and it's none of them. And it has all the symptoms of blown headgasket(s). Comp test will confirm it, for sure.
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And it has all the symptoms of blown headgasket(s).
really? ALL of the symptoms?
here are the TOP THREE -

failed the BLOCK TEST -
yours PASSED

no heat from the vents with the cabin temp set to 90* -
you DO have constant HOT heat

white smoke billowing from the exhaust that smell like antifreeze?
you have NO white smoke -
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
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280 Posts
Discussion Starter #73 (Edited by Moderator)
Well, unless those old gm pellets clogged up the heads, I cant find anything else wrong with it.

It has new radiator, purge line flows, pump good, fans work, etc, etc
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,421 Posts
........ and a compression test may not show any problems, either. It's entirely possible that it takes a running engine, with its high cylinder combustion pressures, to blow exhaust gases past the fire rings into the cooling passages. If all cylinders check out between 140 - 170 psi then that's no "failures" there.

Which is why the cylinder block exhaust gas test is the determining test for exhaust gas in the coolant.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
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280 Posts
Discussion Starter #75 (Edited by Moderator)
Itll get overheated just idleing.

I plan on working on it tday, after it warms up. We had a cold snap, after all that warm rain. It's now 30 here, but sunny and no wind. Supps to get 50 later. I should be able to determine SOMETHING about it tday!
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,421 Posts
230 is not overheating - 265 is. If you drive or let it idle in P, how far will it "overheat" before fans go to SLOW, then to FAST ?

If fans go to SLOW at 224 that's pretty close to your "230" mark, but well below the 236 where fans go to FAST - do they ever go to FAST? Does the surge tank blow off coolant during these events ?

You say that if you raise idle rpm to about 1200 - 1500 the temp drops back to the normal 195 - 210 range - where does it run if you drive normally in a suburban environment - can you drive the car several miles with no indications above about 220 or so ?
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
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280 Posts
Discussion Starter #77
When we were working on it last time, we (I) would let it (idleing in yard) get to 230, to see if we fixed anything, then I would raise the idle to cool it down some before shutting it off. I checked the fans, they were on slow, I dnt think I ever let it get hot enough for em to come on high. It used to maintane temp, going down the road, now, no more. Itll go into the 230 after a couple miles.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
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280 Posts
Discussion Starter #78
Sub, you've got me wondering now, if the fans aren't even working on high. I used to remember it always idling in summer, with ac on, and fans kicking on high, then off. But the thing is, it never used to get over 199-200, idlieing.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,421 Posts
Sub, you've got me wondering now, if the fans aren't even working on high. I used to remember it always idling in summer, with ac on, and fans kicking on high, then off. But the thing is, it never used to get over 199-200, idling.
With some A/C compressor function set the fans run in SLOW all the time. In that condition fans should never go to FAST. They should never cycle on and off with the A/C or DEFROST set.

Idling, to get the temp up past 236 (fans to FAST) cover the radiator with cardboard.

230 - are you looking at actual temperature numbers or at a gauge needle ? Our engines use the same temp sender, so even if your car has the smaller gauge then its tick marks are the same temps as mine -

Temp gauge - my numbers.jpg
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
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280 Posts
Discussion Starter #80
Its digital. I ckd it with the IR themometer I sprung 40 bucks for, last time, and after it got all warmed up(hot), I shot the upper hose and compared it to the dash, both were 230. And I fgt to mention, anytime he drives it anywhere now, the "Coolant hot-idle engine" message appears.
 
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