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Engine overheating


Stan S

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99 Concours, 96k mi. Today my wife called to tell me the Caddy was overheating and gave the engine shutdown message. She was about 50 mi. from home so I take her the other car. By the time I got there the engine had cooled so I refilled with water and started home. Temp gage ran normal until I was a few miles from home then it began to climb rapidly. I stopped and refilled with water before the gage got in the red. When I got home I let it cool down and pressure checked for leaks. It held 15# for about 30 min, so there's no coolant leak. I cranked the engine and let it run with the cap off for about 15 min, everything normal. So I start reving the motor and then the coolant started boiling out the surge tank all the while the temp gage is normal. When most of the coolant boils out the temp gage climbs. I refilled the coolant again and installed the cap and now it is setting in the drive running with normal temp as I type this. Why would the coolant boil when the temp gage reads normal? I remember our old guru saying something about the gages read normal through a broad range to keep down customer complaints. I have a service manual but haven't had time to research. The engine has been serviced with the coolant tabs and Dexcool. Water pump and belt replaced, doesn't appear to be any slippage. Cooling fans working. Is the thermostat the next place to look? The FSM mentions something about a thermostat bypass. Does this sound like the dreaded blown head gasket?

Just went out to check on the car, temp is normal, no water out the overflow. I rev the engine about half a dozen times and it starts puking out the overflow. So I'll be waiting to hear from you guys. Hope you come up with an easy fix! Thanks, Stan

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I would read the codes first. Here's a page on how to do that:

http://www.caddyinfo.com/readingcodes.html

Take them down and post them here. The next thing I would do is ask a radiator shop to test the coolant for combustion products, and do a pressure test.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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I know that we have gone over this time and time again. I will NOT make the mistake of saying that this is a head gasket issue until all of the other possibilities are eliminated. Would somebody PLEASE compile a checklist from all of the knowledge and experience of this board to help with the diagnosis of the overheat problem.

I'll start, but Stan has already hit on a few:

Waterpump

Waterpump belt

Waterpump Belt Tensioner

Air Bleed Hose to coolant tank

Collapsed lower hose

Plugged "Hollow Bolt" in throttle body

Thermostat

Coolant Tank Cap leaking/ improper pressure

Coolant not 50/50 mixture

Improper Coolant

Please continue. Thanks!

Never underestimate the amount of a persons greed.

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I think the first thing I'd check is the stat and the purge line. You might try starting the engine cold with the cap off and rev it. If it still pukes out coolant, you have eliminated overheating because the engine is cold. That would be "false boiling" or exhaust gases in the cooling system which would mean a head gasket.

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Thanks for all the replies. Yeah I checked the codes, P1258 history, "engine overheat" ( I think we knew that!) I checked everything Johnny G mentioned, except for the coolant mixture, it's out on the highway somewhere. Coolant and tabs were changed at 60K miles and none has been added so I'm sure it was okay. I checked the stat on the stove in a pot of water, it opened around 180-190. I checked the cap with a pressure tester, it held at 9#, but so did the one off my Chevy PU. Ranger mentioned the purge line, what exactly are you referring to? Also I will check in the morning for the "false boiling. Thanks again, Stan

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Excuse me, but did somebody say that it was a head gasket? Uh, I suggested eliminating the head gasket first. It's simple and easy to do. And, the pressure test will likely reveal things like water pump and hose leaks...

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Ranger mentioned the purge line, what exactly are you referring to?

The purge line is the 3/8" line that runs from the water pump housing to the surge tank. It's purpose is to purge air from the system. If it is plugged, it can cause overheating. Pull the line at the surge tank. It should have a coolant flow. If so, quickly plug it back in. If not, locate and clear the blockage.

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I'm trying to reinstall the thermostat using a new gasket, but am having trouble getting it to seal. When I removed it the seal stayed in the wp housing, but the FSM shows the t-stat installed first, then the gasket (seal), then the housing (hose neck). I've installed both ways but can't get to seal. Anyone done this before can tell me what the trick is? thanks Stan

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It's possible that the thermostat and gasket were put in backwards. Carefully get the old gasket out and clean the sealing surfaces. Use the pictures and text in the FSM to determine how the new gasket and thermostat go in.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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How about the radiator or the electric fans. How do you check a water pump that has failed internally , at the shaft.

My origional post stated the fans were working. As far as the water pump I removed the WP cover and verified it was still working.

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I'll be watching this thread closely, as I too am having an overheating issue with my car. I suspect either the radiator or water pump. Is it possible for the pump to circulate enough coolant at lower engine speeds but not keep up at higer speeds?

Charles

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I finally gave up trying to find the problem. Took it to a local shop this eve. Service manager-owner suspects head gasket. They will diagnose maybe tomorrow and let me know. He quoted approx. $3500 for both head gaskets and timeserts. $7500 installed for a Jasper reman with a 3 yr warranty. Does this sound in line for any of you who have had this work done?

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Funny how all shops automatically conclude that an overheating Northstar has bad headgaskets without doing any diagnostics... Make sure they check the purge line and pressurize each cylinder to verify the integrity of the head gaskets. You want to be absolutely positive that the diagnosis is correct before letting someone rip into the engine. Keep us posted. $3500 isn't a bad price for a Timesert job provided they do the job properly and will offer a warranty on the work.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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  • 2 weeks later...

Update! Heard back from the shop yesterday. The engine is out and the heads removed and sent to the machine shop to have them pressure checked. The bad news is the exhaust lobes on the cams are flat spotted. New cams and lifters about another $1700 on top of the $3500 for the headgasket- timesert job. So much for those wide open runs and "drive it like you stole it" line of thinking! Getting real close to the cost of a reman engine. I guess hindsight is 20/20? Must say I am real discouraged with the Northstar at this point. This will be more money spent on one engine than than I've spent for repairs on the 16 other vehicles I've owned in the past 40 years.

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Stan, I don't think that cam problem is from WOT. It would seem to me that it is an oil supply problem, otherwise your intake cams would be in the same condition. I'd have them check to be sure that the oil ports are all clear. Have you used any additives?

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this is why i push so hard for the CO2 exhaust test these days.

all the other tests are a PITA .. for anyone, a PITA.

Stan will NEVER know if the headgaskets were a problem.

something that could have been verrfied in 10 min and less than $100.

hell, even a non-car guy can do the test - no mechanic needed.

what is $100 vs $3,500 ? next to nothing.

these days, at the other site, it seems i see a new headgasket car issue

every single day, day in, day out.

the headgasket issue is so prevalent on these N*'s that everyone that

comes across my screen with a overheating, i tell them to do the CO2 test ASAP.

sadly to say, the headgasket batting avg is over 50% .. it is a fast yes / no test.

============================

Stan,

i agree 100% with RANGER. the WOT is no way going to do that to the

cam lobes, not in 50,000 miles, not in 100,000 miles, not even in 200,000 miles

it is either a oil flow problem or a bad batch cam that didn't get hardened properly.

you can actually have the lobes checked for hardness if you had a warranty

problem.

.

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I had a Quad 4 HO in a 1990 Pontiac Grand Am. This little 2260 cc motor is an ancestor of the Northstar (which started life as a Quad 8). The rev limiter was set at 7,200 and I knew just when to shift. It had flat lifters and DOHC, just like the 1993-1999 Northstar. The oil filler cap said 5W-30 and I always used synthetic oil. When I traded it for my Cadillac at 85,000 miles after seven years, it still had the original cams and would scat well enough to startle most people. I still miss the Level III suspension, but my wife's 1999 Grand Am has it now.

Want to humor us? Ask them for your old cams. Take pictures of the lobes and post them here.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Want to humor us? Ask them for your old cams. Take pictures of the lobes and post them here.

Yes! Pictures by all means (if you'd care to).

Just shoot some photos at the shop. If you're anything like me don't bring those cams home!! They'll still be on a shelf somewhere when you sell your home someday. :P

Regards,

Warren

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I finally gave up trying to find the problem. Took it to a local shop this eve. Service manager-owner suspects head gasket. They will diagnose maybe tomorrow and let me know. He quoted approx. $3500 for both head gaskets and timeserts. $7500 installed for a Jasper reman with a 3 yr warranty. Does this sound in line for any of you who have had this work done?

What did the service manager owner do to suspect head gaskets. Did they test the coolant for combustion by products?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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this is why i push so hard for the CO2 exhaust test these days.

all the other tests are a PITA .. for anyone, a PITA.

Stan will NEVER know if the headgaskets were a problem.

something that could have been verrfied in 10 min and less than $100.

hell, even a non-car guy can do the test - no mechanic needed.

what is $100 vs $3,500 ? next to nothing.

these days, at the other site, it seems i see a new headgasket car issue

every single day, day in, day out.

the headgasket issue is so prevalent on these N*'s that everyone that

comes across my screen with a overheating, i tell them to do the CO2 test ASAP.

sadly to say, the headgasket batting avg is over 50% .. it is a fast yes / no test.

============================

Stan,

i agree 100% with RANGER. the WOT is no way going to do that to the

cam lobes, not in 50,000 miles, not in 100,000 miles, not even in 200,000 miles

it is either a oil flow problem or a bad batch cam that didn't get hardened properly.

you can actually have the lobes checked for hardness if you had a warranty

problem.

=============================================================================

I think we are experiencing the same problem with our '98 STS; 139,000 miles; never an overheating problem. Suddenly, periodically, it ran a little warm; this weekend, temp. guage shows 3/4 mark; goes back down with rest, but elevates again pretty quickly. I changed the thermostat Sunday night; no help. Monday, I changed the water pump and belt; no help.

About a month ago, I did have to replace the starter; PITA!!! Why is the dang thing under the intake????? With the aide of a service repair manual, it was not a big job; went pretty well, I thought. Now, I am wondering if I did something to cause this overheating problem.

I have read all of these posts on here about headgasket problems; it sounds like we are headed that direction also. My question is, WHY??? Are these engines prone to do this after a period of time??

.

My "other car"

100_05472.jpg

1968 Pontiac GTO, 400, 4 speed, 366 h.p., matching numbers car

*Get well soon, John Force!!!*

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these days, at the other site, it seems i see a new headgasket car issue

every single day, day in, day out.

the headgasket issue is so prevalent on these N*'s that everyone that

comes across my screen with a overheating, i tell them to do the CO2 test ASAP.

sadly to say, the headgasket batting avg is over 50% .. it is a fast yes / no test.

============================

Stan,

i agree 100% with RANGER. the WOT is no way going to do that to the

cam lobes, not in 50,000 miles, not in 100,000 miles, not even in 200,000 miles

it is either a oil flow problem or a bad batch cam that didn't get hardened properly.

you can actually have the lobes checked for hardness if you had a warranty

problem.

.

Keep in mind that for every Northstar with bad headgaskets, there are thousands of them running around without any issues. Internet forums tend to exaggerate issues because it is where prople come to seek help for problems or to vent.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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