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99 Deville Overheating when driven over 60MPH


PAUL T

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My wifes' Uncle has a 99 Deville. It started overheating so they took it to a dealer who checked it for leaking headgaskets and said it was not the headgaskets. I think they pressure checked it. He had a new waterpump and belt put on. Tensioner is tight, coolant is 50/50 and full and the Fans are working. I haven't checked the hose into the surge tank yet. He claims that it only overheats when you drive it over 60MPH for less than a mile. He said as long as you keep it under 60 it does not overheat. He thinks maybe it is a plugged up Catalytic converter, but it seems to run just fine. The codes are as follows.

Current Code

P1483

History Codes

B1327

B1350

B1147

B1148

B1152

B1161

U1000

Anybody with any ideas let me know and I will check it out. If I come up with anything else I will let you know.

New info, it has a new radiator and the purge line is clear and the bottom hose is not collapsing.

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Thermostat? Let him check out the upper hose when it overheats.

I think he said the thermostat was new. It is possible the upper hose could be collapsing. I am going to take it out if I get a chance and check the upper hose.

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B1327 - Vehicle system voltage below 9.0 volts

B1350 - Engine Coolant Over-Temperature

B1147 - Driver Side Air Bag System Malfunction

B1148 - Passenger Side Air Bag System Malfunction

B1152 - Data Area Full

B1161 - Lamp Circuit Failure

P1483 - Engine Cooling System Performance

I would have thought a water pump belt. Since it only occurs over 60, its not related to the fans. As long as you keep it under 60 its fine, very odd.

The first thing I would look at is the purge line, and tank nipple to be sure they are flowing and open. Maybe it cavitates at a certain rpm. Personally, I can't help but think that this is a head gasket problem, but your idea of a collapsing hose on the draw side of the pump is a good one.

You don't have any tranny overheat codes either so its not related to the tranny.

Maybe a clogged radiator that can't flow enough coolant at a set rpm?

Could the tar paper air deflector be blowing up and covering the radiator at 60? :P

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B1327 - Vehicle system voltage below 9.0 volts

B1350 - Engine Coolant Over-Temperature

B1147 - Driver Side Air Bag System Malfunction

B1148 - Passenger Side Air Bag System Malfunction

B1152 - Data Area Full

B1161 - Lamp Circuit Failure

P1483 - Engine Cooling System Performance

I would have thought a water pump belt. Since it only occurs over 60, its not related to the fans. As long as you keep it under 60 its fine, very odd.

The first thing I would look at is the purge line, and tank nipple to be sure they are flowing and open. Maybe it cavitates at a certain rpm. Personally, I can't help but think that this is a head gasket problem, but your idea of a collapsing hose on the draw side of the pump is a good one.

You don't have any tranny overheat codes either so its not related to the tranny.

Maybe a clogged radiator that can't flow enough coolant at a set rpm?

Could the tar paper air deflector be blowing up and covering the radiator at 60? :P

It was overheating before, that is why so many parts have been replaced. Dealer was supposed to check the head gaskets and said that was not it. I do not know how they arrived at that though. There is no steam from the tail pipe or coolant in the oil at this point. Purge line was clear. He told me he ran it with the thermostat out and it still overheated. I am leaning toward maybe a clogged or partially clogged metal line around the back of the engine. I inspected the tensioner on the waterpump and it seems to be holding the belt tight. I will check the tar paper deflector. I will keep checking.

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This does not sound good. I would try to find out EXACTLY how they determined that the head gaskets where OK. One would think they know how to do it correctly, but it would not be the first time a dealer has misdiagnosed a problem.

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Can it be air in the cooling system. Isn't there a air bleeder near the water pump? try bleeding the cooling system.

The system is self purging.

Unless the purge line is clogged, and Paul said he did not check to see if the line was clear yet.

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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He did Mike.

"It was overheating before, that is why so many parts have been replaced. Dealer was supposed to check the head gaskets and said that was not it. I do not know how they arrived at that though. There is no steam from the tail pipe or coolant in the oil at this point. Purge line was clear. He told me he ran it with the thermostat out and it still overheated. I am leaning toward maybe a clogged or partially clogged metal line around the back of the engine. I inspected the tensioner on the waterpump and it seems to be holding the belt tight. I will check the tar paper deflector. I will keep checking."
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He did Mike.

"It was overheating before, that is why so many parts have been replaced. Dealer was supposed to check the head gaskets and said that was not it. I do not know how they arrived at that though. There is no steam from the tail pipe or coolant in the oil at this point. Purge line was clear. He told me he ran it with the thermostat out and it still overheated. I am leaning toward maybe a clogged or partially clogged metal line around the back of the engine. I inspected the tensioner on the waterpump and it seems to be holding the belt tight. I will check the tar paper deflector. I will keep checking."

Oh sorry, I didn't see Pauls update, I saw this in the first thread "I haven't checked the hose into the surge tank yet."

Not good at all.. Its possible that it could pass a cooling system test and fail a compression test, I suppose, but its happening once the engine reaches 1850 to 2000 rpm or so...

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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describe the scene here? motor gets hot over 60mph. what happens when you slow down? is your coolant level dropping? are you loosing coolant? does the motor get hot but not boil over? keep it in 3rd gear around town. that will get the rpm's up and perhaps tell you if it is rpm related which might point to coolant flow issues.

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Was the thermostat replaced with an ACDelco? Haven't members here had problems with aftermarket thermostats?

WARNING: I'm a total car newbie, don't be surprised if I ask a stupid question! Just trying to learn.

Cheers!

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Was the thermostat replaced with an ACDelco? Haven't members here had problems with aftermarket thermostats?

Lothos,

He was driving without a thermostat for a while, still overheated.

The saddest thing in life is wasted talent

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describe the scene here? motor gets hot over 60mph. what happens when you slow down? is your coolant level dropping? are you loosing coolant? does the motor get hot but not boil over? keep it in 3rd gear around town. that will get the rpm's up and perhaps tell you if it is rpm related which might point to coolant flow issues.

I find that when I put my selector in 3, my temp goes down because the engine turns faster, turning the WP faster. I can't help but think this IS rpm related, and that the head bolts are pushed up at higher rpm. I think a coolant combustion by-pass test would be smart at this time.

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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The system has been pressure tested twice. The first time the pressure was left on it overnight and no pressure loss. The second time it was done there was a leaking hose clamp. Thermostat was replaced by a dealer so I am pretty sure it is GM. It does seem to be RPM related. It is not leaking now unless it overheats. Right now it is not running a 50/50 mix because he only had water to add the last time it overheated just to get home. My wife's uncle seems to be leaning toward a plugged up cat-con but it runs too good for that and I can not see the connection. He is an old school mechanic so I don't dare question him but this is his first Northstar. I bought him a set of books for it, a while back, but I don't think he has got them out of the box they were shipped in yet. I may get to look at it again today.

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You note that the purge line is clear, is the hollow bolt clear?

On a cold engine, remove the radiator cap, disconnect the purge line and coolant should flow out of the hose and the hollow bolt.

If coolant does not come out of the hollow bolt, I would remove the hollow bolt from the engine, and clear it with a drill of the same size as the original hole.

Then replace the hollow bolt to the engine. Removing the bolt makes it safer to clear; no metal or broken drill bit to get out of the engine.

Has the radiator been tested for internal blockage (Excessive Bars Leak)?

The radiator might flow enough coolant for low speed demands, but not enough for higher speed cooling.

Doing the above will cause coolant loss, be ready to temporarily block the coolant openings while you work.

-George

Drive'em like you own 'em. - ....................04 DTS............................

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You note that the purge line is clear, is the hollow bolt clear?

On a cold engine, remove the radiator cap, disconnect the purge line and coolant should flow out of the hose and the hollow bolt.

If coolant does not come out of the hollow bolt, I would remove the hollow bolt from the engine, and clear it with a drill of the same size as the original hole.

Then replace the hollow bolt to the engine. Removing the bolt makes it safer to clear; no metal or broken drill bit to get out of the engine.

Has the radiator been tested for internal blockage (Excessive Bars Leak)?

The radiator might flow enough coolant for low speed demands, but not enough for higher speed cooling.

Doing the above will cause coolant loss, be ready to temporarily block the coolant openings while you work.

-George

Purge line flows freely so hollow bolt must be clear. Radiator is new. I will have to ask about the use of bars leak and where it was put in.

Update: I just got it to spew out antifreeze. Cooling fans are kicking on at about 220-222 degrees f. After the fans kicked on it went back to 213. After running at about 3000 rpm for about 5 minutes or so coolant started spewing out of the surge overflow, temp. was back up to 224 and the fans were on. My wife's Uncle has never put bars Leak or anything like it in. He does not know about the previous owner though. I would like to pull the surge tank out and check the bottom hose but I leave for home tomorrow and I do not know if I will have time. There are no leaks and no antifreeze in the oil or tailpipe. The concentrata was less than 50% antifreeze so I expected a low temp. boil over.

Can the "T" connection in the hoses cause overflow if it is not in correctly? He is talking about taking it to the radiator shop to have the system back flushed to check for clogs or partial clogs. He also says the thermostat is in correctly. I cleared the codes before I started and the only code that came back was SDM "B1152". I do not think that pertains to the problem.

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After running at about 3000 rpm for about 5 minutes or so coolant started spewing out of the surge overflow, temp. was back up to 224 and the fans were on.

Paul T,

That seems like an awful low temp to have a BOILOVER.

Is this a pressurized surge tank?

Is it possible that it is nothing more than a bad pressure cap that is not holding the pressure that it is supposed to?

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Update: I just got it to spew out antifreeze. Cooling fans are kicking on at about 220-222 degrees f. After the fans kicked on it went back to 213. After running at about 3000 rpm for about 5 minutes or so coolant started spewing out of the surge overflow, temp. was back up to 224 and the fans were on. My wife's Uncle has never put bars Leak or anything like it in. He does not know about the previous owner though. I would like to pull the surge tank out and check the bottom hose but I leave for home tomorrow and I do not know if I will have time. There are no leaks and no antifreeze in the oil or tailpipe. The concentrata was less than 50% antifreeze so I expected a low temp. boil over.

It's very important in these cars to have a 50/50 mix

WARNING: I'm a total car newbie, don't be surprised if I ask a stupid question! Just trying to learn.

Cheers!

5% discount code at RockAuto.com - click here for your discount!

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