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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
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280 Posts
Discussion Starter #1
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!
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
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68,423 Posts
No need for snake oil cleaners. The coolant purge line or hollow bolt/nipple on the water crossover is most likely plugged. The purge line should flow a small steady stream from the crossover nipple to the surge tank upper side.

Google "cadillac forums northstar coolant purge line".

When was the last time you checked the water pump drive belt and tensioner pulley?

Pulley and tensioner (Notes).JPG
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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280 Posts
Discussion Starter #3 (Edited by Moderator)
Thanks Sub. The purge line is clear. We just replaced the coolant crossover gaskets, the other day, what a job. Everything got inspected and cleaned. I dont know what else to do, Sub. Everytime I read bout somebody with Nortstar overheat, I always say to myself, "Head gaskets", and that's usually what it is, but I cant confirm it on this car.

It's got new tensioner, belt and pulley. After it gets to 230 at idle, I can raise the rpms to bout 1300 and itll come back down to 212-216, I can keep doing this until the all the coolant gets hot, so it's got good flow. On my 99 Deville, when the gaskets went, I could blow thru the #1 cylinder by mouth and hear bubbles in the expansion tank! But it would idle all day long and never get hot. Just couldnt drive it. It was using coolant, this one uses no coolant and gets hot idleing.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
Any chance your surge tank cap is not sealing and holding pressure?
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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280 Posts
Discussion Starter #5 (Edited by Moderator)
Na, it never boils over, or loses any coolant. It's a good cap. Thanks, Ranger.

It all started after I gave the car to my girlfriends kid. It never overheated on me. I went coast to coast, New Orleans, thru Death Valley in the summer, etc. NEVER, got hot. It sat for several months, after I got my CTS and as soon as he got it it started overheating and ruined the radiator. I put a new one in, with some more gm pellets, (just bfre I read not to use em anymore), but it was never the same after that. Started running a little warm, in the teens, then the twentys, and a few months later, in the 230's now. Itll go higher, but dont let it.

Since it wasn't using any coolant, I thought maybe I clogged up the little cooling passages in the headgasket with the gm pellets. I've flushed all the coolant out and put Blue Devil radiator cleaner in it, and been starting it every day for last 3-4 days and letting it run up to 230. Dont look like its gonna work.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,423 Posts
Have you driven the car for an hour or so at different speeds to see if maybe there's an air lock somewhere ? Does the HVAC have good heat output and temperature control of that heat? (The heater core is full flow at all times - air temp is changed with cool air blending.) Are both heater core pipes at the firewall HOT ?
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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280 Posts
Discussion Starter #7
Thanks, Sub, yea, it puts out good heat and theres no air left in it. The expansion tank took 3/4 gallon water the next day, after it sat overnite, after the coolant fill up. The heater hoses are hot. Top hose HOT n hard. Cant drive it but half mile till it goes in the 230+.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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280 Posts
Discussion Starter #8
I posted awhile back about this problem. Car was still drivable then. Then it blew crossover gasket, after that fix, which is now, car is undriveable. Must be a headgasket leak, if it is, I dnt think it's worth fixing. Sad, because it's a good ole car. New front end, struts, bushings, new bushings in rear. Rebuilt tranny, torque converter n flex plate. No rust or dents. Now it's got new crossover gaskets and hoses. New acdelco 02 sensors. Great tires and rims. I guess next thing is to do a compression ck, and hook the air compressor up to each cylinder, with the valves closed, n see what happens. Unless y'all can think of something different?
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
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86,781 Posts
Did you perform the block test right after an overheat episode? That's the time to do it, when it would still have combustion gasses in the tank (if there are any).
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,423 Posts
Is the water pump original? Once in a blue moon a w/p will shed the blade shroud ("top hat") that is necessary for proper pumping ability ......... where the "from heater circuit........" arrow points.

water pump capsule 2.jpg
water pump capsule.jpg


 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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280 Posts
Discussion Starter #11
Thanks, Ranger, Thanks, Sub. Yea, we changed the water pump, just bfre the crossover gasket blew. Fgt to mention that. The last (2nd) block test was done immediately after a short drive to 230+ degrees. Tested for about 10 minutes. I had to remove it slightly at the end, to keep the coolant from bubbling into the liquid, it was steaming so hard, so I'm sure if any hydrocarbons were there, they would have gone thru that pretty blue liquid. It never changed color at all. Maybe my fluids no good, and I should get new? There is no coolant in the oil, either. That's what I dnt get, like I said earlier, all the N* overheat posts I've read over the years, when the owners said they ckd everything, and it passed the block test, I said to myself, "headgaskets", and sure enough, after a 2nd block test, or so, the fluid would turn yellow or green. I'm thinking headgaskets this time, but I cant get the fluid to change color. Do ALL N* headgasket failures cause a failed test?
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,423 Posts
The test fluid changes color with ANY presence of exhaust gas hydrocarbons. Do a test at the tailpipe with the engine idling.

If you're not getting color changes then the head gasket(s) are OK. There is NO reason for excessive test/bubble times. 20 - 30 seconds is all it takes. Don't try to "make it better".

Do you have, or can you borrow, an IR thermometer? Shoot the water pump cover and heater core lines at the firewall for system temperatures.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
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86,781 Posts
You won't see any coolant in the oil on a Northstar.


Do ALL N* headgasket failures cause a failed test?
Not always in the early stages, but based on what you said, it sounds like a HG and well past the early stages.



It never changed color at all. Maybe my fluids no good, and I should get new?
I've never used the stuff and don't know if it can go bad, but I suppose it might be a possibility.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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280 Posts
Discussion Starter #14
Thanks, Sub, thanks, Ranger. Good idea on tailpipe, I'm trying to think how I'm gonna do that. And the IR thermo meter too, I'll get one. Thanks guys!
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
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86,781 Posts
Sub's idea of doing a test at the tail pipe would verify that the test fluid is good if it changes color. Good idea.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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280 Posts
Discussion Starter #16
Yea, I'm trying to think how I'm gonna do a test at tailpipe.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
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86,781 Posts
Just hold the tester near the pipe and draw in exhaust gasses. If the fluid is good, it will change color.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,423 Posts
Yep - the tester measures gases, not liquids. Any coolant gets into the test fluid, you clean and wash out the tester and start over.

Some of the testers come with a vacuum squeeze bulb, some come with a line you tap into manifold vacuum. In any event, you draw bubbles through the test fluid - no coolant.
 

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1999 Deville base
95 Eldorado, 99 Deville, 05 CTS
Joined
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280 Posts
Discussion Starter #20
K, I have a cheap little plastic one that you press n hold into the expansion tank neck, I'll rig something to that. I guess I'll pick up a Ir thermometer at Wallyworld, since I need it now.
 
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