1998 Cadillac Eldorado 4.6 Northstar Overheating

Reply

  #1  
Old 07-15-08, 04:30 AM
billys68ss's Avatar
Member
Thread Starter
Join Date: May 2003
Location: USA
Posts: 1,459
1998 Cadillac Eldorado 4.6 Northstar Overheating

Hey guys, Im hoping for a little help here. I have one of those PITA cars in the shop right now that I cant seem to figure out. The car is a 1998 Caddy Eldorado 4.6 V8 Northstar. It is overheating. I can drive it around town at lower speeds and it does fine. As soon as I hit the highway 70mph and the temp starts to rise. Before Ive gone a mile or so it is full hot. As soon as i get off of the highway it starts cooling down. It takes less than 5 miles and its back down to halfway. It can sit in the shop for hours running and it never goes above halfway. I have replaced the water pump and thermostat. I have also replaced 2 of the ran relays. I am at a loss...
Help Please!!!
Thanks in advance Guys,
Billy
 
Sponsored Links
  #2  
Old 07-15-08, 09:45 AM
Member
Join Date: Jun 2008
Location: Eastern Georgia
Posts: 486
Had a Trans Am do the same thing to me, turns out the air deflector that bolts to the core support under the car was broken off. At idle or low speeds the electric fans could keep up, but put it on the highway and away went the temp. The deflector on this car was just 1 or two inches wide but made all the difference in the world.
 
  #3  
Old 07-15-08, 03:22 PM
billys68ss's Avatar
Member
Thread Starter
Join Date: May 2003
Location: USA
Posts: 1,459
Well thats certainly something to think about and look at. Thanks!
Just a little more info... This all started we put a radiator in it. My tech drove it and it was fine. It went back on the lot, a week later it was sold, a week later it came in overheating. Ive had it ever since. I have tested for a cylinder head gasket leak 3 times just to make sure. I did replace a bad radiator cap as well, but so far nothing I have done has had any positive effect.
Thanks again,
Billy
 
  #4  
Old 07-15-08, 03:32 PM
Unclediezel's Avatar
Member
Join Date: Dec 2006
Location: Northeastern PA.
Posts: 2,230
Look at the lower hose while revving the motor......During rad replacement, if the "SPRING" fell out of the hose, it will collapse under load and close the hose off....Also... Over the years Ive had several radiators that came out of the box defective........

Until you said water pump replacement, It sounded like the impeller came loose on the pump shaft....Was the impeller intact and accounted for when you took the original pump out??????No plastic "CHARDS" lodged where they shouldnt be?
 
  #5  
Old 07-15-08, 04:50 PM
billys68ss's Avatar
Member
Thread Starter
Join Date: May 2003
Location: USA
Posts: 1,459
The impeller was intact. The water pump was the first thing I thought of and im glad I did because when I got it out, I saw that someone had installed a junk yard water pump. I couldnt believe that. So I replaced it with a brand new one and also replaced the thermostat at the same time. I dont really care for the camshaft driven water pump, but obviously it works. I havent thought of the hose because frankly I have never actually observed that. Ive seen the springs rot away, but thats about it.
Billy
 
  #6  
Old 07-11-09, 12:09 PM
Member
Join Date: Jul 2009
Location: USA
Posts: 1
What ended up being the problem on this 1998 Cadillac Eldorado 4.6 Northstar Overheating do you rember? Her was your post



--------------------------------------------------------------------------------
1998 Cadillac Eldorado 4.6 Northstar Overheating



Hey guys, Im hoping for a little help here. I have one of those PITA cars in the shop right now that I cant seem to figure out. The car is a 1998 Caddy Eldorado 4.6 V8 Northstar. It is overheating. I can drive it around town at lower speeds and it does fine. As soon as I hit the highway 70mph and the temp starts to rise. Before Ive gone a mile or so it is full hot. As soon as i get off of the highway it starts cooling down. It takes less than 5 miles and its back down to halfway. It can sit in the shop for hours running and it never goes above halfway. I have replaced the water pump and thermostat. I have also replaced 2 of the ran relays. I am at a loss...
Help Please!!!
Thanks in advance Guys,
Billy
 
  #7  
Old 07-12-09, 12:46 PM
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 8,629
Your engine gets hotter with increased load and wind-load and rpm's at higher highway speeds. Cooling has a harder time keeping up then if you have say an air pocket and you can be decieved that you are full of coolant, or if a radiator hose is partially collapsed, or if the radiator is plugged with lime scale.

I had your same symptom and ended up changing the radiator to fix it. Radiator was plugged with lime. With such a poor circulation problem - if you ran the car with the radiator cap off on a test - when the thermostat opens, the water will rush in at the upper hose to the top of the radiator and gush out at the open cap hole, since it can't circulate through the radiator fast enough, as a tip off that you have a restriction.

You might be able to make such a test also if you remove the thermostat and put the housing back on without the stat inside, then run the engine. You would know something in about 1 second.

You could also try running a garden hose through it. But this test did not help me, as I do not have the greatest flow volume, and all the hose water easily went through the partially clogged radiator. It might depend on how much water can go through your hose.

You might get results by pouring water through it with a pail and some hand made wider-bottom funnel, so you can pour more water in quickly. [With the last 2 paragraph ideas, which includes this one, you would have to drain the radiator/salvage your coolant, and remove the bottom radiator hose, so that water goes through the radiator and out the bottom.]

Lower radiator hoses have been known to collapse, and you might want to buy a new one of these and try that. Or remove it completely, if you can get at it, and inspect.
 
  #8  
Old 07-27-09, 01:22 PM
Member
Join Date: Jul 2009
Location: wisconsin
Posts: 1
2000 sls 4.6 northstar

have sort of the same problem as you did you ever get it fixed? what was the answer? please help
 
  #9  
Old 07-28-09, 06:44 AM
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 8,629
Yes. After I left the radiator cap off and ran the engine until the engine warmed up and then the thermsotat opened, old faithful geyser came out the top of the radiator!!, and that clinched it for me that the radiator was plugged(not letting enough water freely circulate through it), and I changed out the radiator and that fixed the car. Did it myself. Bought brand new radiator for pretty cheap ($106) from a salveage yard of all places.

I had also tried running hose water through the radiator. First I drained and saved engine coolant from the radiator, then disconnected lower radiator hose and saved coolant that ran out of it, then stuck hose in open radiator cap and observed if all the water entering from the hose wide open could exit the bottom of the radiator. It did. But that is a poor indicator since my hose was not putting out the volume that the car's water pump can. My radiator was about 50-70% plugged, not 100% plugged - that's why.

Also, read other posts about engines overheating, and possible causes. Also check to see if service bulletins exist on your vehicle that list similar problem, for that year and or mileage.

A vehicle has to have a clear radiator, lower hose that is not collapsing, a water pump that turns with the belt being tight, no air bubble at stat, a properly functioning stat, a properly functioning temp sending unit to the computer, a properly functioning fan relay, and a fan that works (or sometimes 2 fans).
 
  #10  
Old 05-04-10, 07:34 PM
wiillix's Avatar
Member
Join Date: May 2010
Location: USA
Posts: 12
These cars from 96 to 99 are notorious for head gasket failure. Poor block casting leave blocks with a porosity that allows corrosion to contaminate the head bolt threads and basically rip the threads right out the block & causing the the head to lift. Its a costly repair that will cost $3000 to $6000 to have it done properly. There are many resources that can be found at this site. Read though this thread it goes fast and has good onfo http://http://www.cadillacforums.com...ilure-fix.html
 
  #11  
Old 05-05-10, 06:23 PM
Banned. Rule And/Or Policy Violation
Join Date: May 2007
Location: Wisconsin
Posts: 8,629
If this is really true - then could one easily tell that is indeed what happened, by simply seeing what happens if you try to retorque the bolts? Wouldn't they be loose enough to retighten (and/or just spin in circles?), if they(bolts) are rippng right back up through the block threads?

Reading stuff like this makes one wonder how we ever made it to the moon in the 60's, eh?
 
  #12  
Old 05-05-10, 09:59 PM
xjfish's Avatar
Member
Join Date: Sep 2009
Location: MN
Posts: 26
Miles on the car? Sounds like its time to have the head gaskets done. I've replaced a couple on these cars with the exact same symptoms, not a fun job (Over 20 hours flat rate). It is important that time-serts be used. If anyone else is reading this with a Northstar vehicle, change out the old GM dexcool coolant asap if you haven't already. I'll try to pop back in on this thread, but if anyone is looking for specific advice, shoot me a PM and I can try to help.
 
  #13  
Old 05-06-10, 08:45 PM
Join Date: Jul 2009
Location: Washington State
Posts: 312
Hey uh Guys the OP was July of 08 although lots of good info on these northstars.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes