'00 Cadillac DeVille - really overheating?

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Old 06-02-13, 09:39 AM
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'00 Cadillac DeVille - really overheating?

Please help! I'm looking at my pastor's 2000 Cadillac DeVille DHS with the 4.6 litre NorthStar V8 because he says it's overheating. DTC's are P0420 (high coolant temp), P1258 (low catalyst efficiency), P1359 and P1360 (ignition control circuits). So, sure enough. it appears to have gotten hot at least once, clipped ignition to both banks and showed a rich mixture in the catalytic converter. Am I thinking correctly so far or am I missing something? My pastor has since had the water pump and thermostat replaced (not by me) but either the problem persists or the codes weren't cleared. Here's what I've found - using a leaking cooling system tester, the cap lets go at about 14 psi (it's rated at 18). Since the tester leaks, I haven't been able to pressurize the system yet but will borrow a tester from my parts store tomorrow. Also, while looking for any coolant residue or evidence of "steam cleaning" on the spark plugs, I did a compression check on the engine. This yielded a low of 175-180 psi and a high of 195-200 psi. Only one cylinder showed the low number and none of the plugs looked like they had been wet. I've done just a little research on the NorthStar and it seems to have head gasket issues. With over 109,000 miles on it and a $3500 quote to replace the gaskets (money I know the owner doesn't have), I'm really hoping to be able to give him some better news than that he doesn't have a car anymore. Hopefully the cooling system pressure test tomorrow will reveal more, but does anyone have any advice as to what else I can look at in the meantime? Thanks in advance for any help - Chris
 
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Old 06-02-13, 10:01 AM
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I think you're doing okay so far; you're probably at a standstill until you get a good pressure tester on it. The compression test doesn't look too bad, so cross your fingers on the pressure/leak test.
 
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Old 06-02-13, 10:21 AM
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Thanks tow-guy. I was afraid of that, but figured that would be the case. I'm hoping that will turn out good too - the engine's not putting water in the oil or in my driveway. And while we drove it the 8 miles from where my wife works to our house (she followed in her car), she said it never made steam out the exhaust. At this point I would be happy to replace the pressure cap and radiator if they're both bad! Just to get ahead a little - is there a procedure to follow to ensure there's not an air pocket in the block not letting the coolant circulate? Thanks again... Chris
 
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Old 06-02-13, 12:22 PM
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I know you said the codes were never cleared. I would do that first so you would have a current playing field to start with. Then attack the coded problems that persist.
 
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Old 06-02-13, 01:28 PM
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Thanks chandler. Good idea. Will do that after pressure test and before test drive tomorrow once I replace the cap. Additional information I forgot to include in my original post: the information center in the instrument panel gives the message, "CHECK COOLANT LEVEL". When I did, the tank is full or over. Is the sensor in the tank and does it detect high, low or both? This is easily the most sophisticated, electronically supervised vehicle I've ever had my hands on and since it's not mine, I'm having to do this without the benefit of a manual. Not the way I usually do things, but... Thanks again for all the input so far - Chris
 
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Old 06-02-13, 01:40 PM
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Typical is just to indicate a low level...but very likely it is checking both. Sensor should be in the overflow.

Take some out to the correct level and it will probably go away.
 
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Old 06-02-13, 07:49 PM
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My Volvo would show that warning if the coolant overflow bottle was low, so it may be that, rather than the radiator. Similar to a low washer fluid warning.
 
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Old 06-03-13, 03:33 AM
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Thanks gunguy and again chandler. A little more investigation showed the sensor to indeed be in the tank. Today I will draw some coolant out and see if the message goes away. Going to pressure test the system today too. I really hope for good results - this pastor is the man who married me and my current wife. There's no way he could afford to replace his car with even a bicycle, and he's such a nice guy. Okay, sorry for the diversion. I'll post results as soon as I can. Thanks again - Chris
P.S. - chandler - like your signature tag. If I read it correctly, and you're somewhat to the right of Pelosi/Feinstein/Bloomberg/Obama, then keep the faith; Stand and Fight.
 
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Old 06-03-13, 10:51 AM
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Bummer. Cooling system pressure test makes drips on both sides of the block. Can't really get underneath to see where they're starting, but I suspect the head gaskets. At least it's external leaks and not internal. The owner is okay with trying a product called Blue Devil Sealer. I've not ever heard of it, but my friend's regular mechanic says if anything is going to work, that's it. I hate the idea of throwing a band-aid on it, but if it will buy my friend a little time to decide what do do, and he's cool with it,... Thanks for everything, guys. 'Til next time - Chris
 
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Old 06-03-13, 03:03 PM
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Too bad with the prognosis, but at least you gave it your best shot. To answer your question, I am so far to the right of those folks if they were facing East, I would be one step to their West. Don't get me started. Be cool.
 
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Old 06-03-13, 06:09 PM
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Okay, I take at least a little pride in doing a job right, whether I'm being paid to or not. But it seems my pastor friend paid another mechanic $600 to replace the thermostat and water pump in this Cadillac. Imagine my surprise when I went to pull the thermostat out (following the Blue Devil instructions) and IT WASN"T THERE! Now, correct me if I'm wrong, but won't the system actually cool better with a thermostat in place?
On the plus side, it appears that Blue Devil is made from the active ingredients in black pepper and chicken eggs... It actually seems to have cured the drips under pressure. And the pump appears new, as far as I can tell. While idling the engine for the required 50-minute cure time, however, the temp did climb high enough for the information center to tell me it was not happy and was shutting the A/C off. And I also found multiple leaks in the coolant tank, so I'll be replacing that when there's money, too.
So, to recap, I've got major leaks taken care of, and I've got system flow. After replacing the 'stat and tank, is there anything else I should look at? I couldn't find anywhere to bleed air from anywhere, like the space in the radiator above the hose necks - should I apply vacuum to the system before filling it next time? This is such a bizarro engine to me, and I don't want to learn anymore about it! Seriously, though, thanks for the encouragement, support and compassion from all so far. More as it happens. - Chris

Tell me about it, chandler. If I'm traveling North and want to go West, I have to make three right turns. Stay strong.
 
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Old 06-03-13, 06:57 PM
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There are no right turns in the south. All left turns around an oval. Ask Richard Petty. But politically, you are correct.
 
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Old 06-04-13, 04:43 AM
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I don't know if "cool better" would be the right description, but the thermostat should be there. Without it, in theory, the engine will be running below its designed operating temperature and that would affect a number of things going on under the hood. When you removed the thermostat housing did it appear it had been off recently? Perhaps it had been removed longer ago than the recent water pump job. The alternative it that the mechanic removed it while doing the pump in order to get a lower temperature as a band-aid fix. My usual cure for air is to elevate the front (car ramps work good) and then bring it up to operating temp with the radiator cap off. Usually when the thermostat opens you get a burp of air out the filler (sometimes gets a little messy because as the coolant warms it will expand and overflow a bit before burping).

As to the leak stop stuff you mentioned, I've heard a couple of mechanics say that the stuff actually works pretty well as band-aids go.
 
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Old 06-05-13, 03:11 AM
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CMil,

Forget about the setting of the error codes and focus on resolving the overheating issue. The North Star engine has problems with overheating. and it's those problems that are setting the error codes. To resolve the overheating problems apply the TSB'S (Technical Service Bulletins) in the link below.

http://www.justanswer.com/cadillac/4...c-deville.html

After the overheating problems are resolved, clear all the codes and drive the car normally. If any codes return, let us know by posting back the codes are that returned.

Thank You
Amy
 
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