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98 deville overheating


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hi guys im new here, ive been a cadillac owner for about 13 years now,an i never owned a northstar engine, so its very hard for me to understand whats going on with my 98 deville , 1st there is no white smoke or coolant in the oil, plus no bubbling in the surge tank. i had the preasure checked and its holding. the temp goes up to about 231 then it fall back down to about 215, then goes back up again then overheats. ive check the purge line and its clear. could the be a water pump? and how can you check to see if it bad. i heard a weird sound coming from it. any information is good. but please dont tell me headbolts or a headgasket, anything but that also i live in central west florida the avg temp here in the summer is about 96 and a heat index of about 117 on very hot days help please

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If the water pump belt is not slipping and it is not leaking, it's good. Get a block test kit from Napa or rent one from an auto parts store that has a rental program and test the air in the surge tank for exhaust gases. Northstars do not put coolant in the oil when a head gasket fails and steam from the exhaust won't show in the early stages and a cooling system pressure test will detect an external leak, but not a bad head gasket.

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If the water pump belt is not slipping and it is not leaking, it's good. Get a block test kit from Napa or rent one from an auto parts store that has a rental program and test the air in the surge tank for exhaust gases. Northstars do not put coolant in the oil when a head gasket fails and steam from the exhaust won't show in the early stages and a cooling system pressure test will detect an external leak, but not a bad head gasket.

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thank you Ranger, by the way in the morning when i goto work , i take the interstate doing about 65-70 and the temp stays at 185 or 190 but when i get off it jumps up to about 201- 221 then fall back down.Is tha a sign of a headgasket leak , headbolt, or waterpump. And i will get a block test done asap. what is you take on this issue?

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thank you Ranger, by the way in the morning when i goto work , i take the interstate doing about 65-70 and the temp stays at 185 or 190 but when i get off it jumps up to about 201- 221 then fall back down.Is tha a sign of a headgasket leak , headbolt, or waterpump. And i will get a block test done asap. what is you take on this issue?

Sounds normal to me, check your coolant level, check the purge line..

When you lift the hood do you smell coolant?

Pre-1995 - DTC codes OBD1  >>

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

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thank you Ranger, by the way in the morning when i goto work , i take the interstate doing about 65-70 and the temp stays at 185 or 190 but when i get off it jumps up to about 201- 221 then fall back down.Is tha a sign of a headgasket leak , headbolt, or waterpump. And i will get a block test done asap. what is you take on this issue?

Sounds normal to me, check your coolant level, check the purge line..

When you lift the hood do you smell coolant?

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no, i dont smell any coolant, if i do have exhaust gases getting into my surge tank, i was thinking about install a 5 psi pressure release valve on the tank (surge)would that help the over heating? i know thars sounds far out but im thinking it might just work

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no, i dont smell any coolant, if i do have exhaust gases getting into my surge tank, i was thinking about install a 5 psi pressure release valve on the tank (surge)would that help the over heating? i know thars sounds far out but im thinking it might just work

Nope, it will just boil over

Smell the tank and see if you smell exhaust fumes. Don't assume that you have head gasket problems yet. It is really hot out, and your temps will be affected by that.

If you can afford it, go to a radiator shop and have them pressurize your cooling system, you are looking for two things, leaks and if it holds pressure. Also see if they can test for combustion by products with a tester...

You need to make sure that your cap is good and that it holds pressure and make sure that your coolant concentration is between 50 and 65% no more and no less.

Its good that you dont smell any coolant. Has the thermostat been replaced?

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/

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will do , thank you very much, man money really tight, cuz i just got married , i just hope its something small, will keep you posted , why would it overheat if i install a blow off valve in the surge tank?

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will do , thank you very much, man money really tight, cuz i just got married , i just hope its something small, will keep you posted , why would it overheat if i install a blow off valve in the surge tank?

Well think of the radiator cap as a 'blow off' valve that blows off at about 16 psi, boiling from any reason will blow it off

If you put a 5 PSI blow off valve in the cooling system, it will blow off VERY quickly, standard pressures are between 12 and 15 PSI, once the 5 PSI blow off blows, you will spontaineously boil due to a loss of system pressure. Go back to basic science and think about it water at sea level boils at 212 degrees, under pressure it boils higher, at 16 PSI it boils a lot higher than it does at 5 PSI.

The bottom line, your cooling system MUST hold pressure at design spec and ALL sources of pressure MUST be repaired in the kind of heat you drive in

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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thank you Ranger, by the way in the morning when i goto work , i take the interstate doing about 65-70 and the temp stays at 185 or 190 but when i get off it jumps up to about 201- 221 then fall back down.Is tha a sign of a headgasket leak , headbolt, or waterpump. And i will get a block test done asap. what is you take on this issue?

No, it's a sign of a normally operating Northstar cooling system. I agree with BBF, those temps sound perfectly normal to me.

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i got the cooling system check tested, it has a very small leak, the Cadillac tech says he doesnt think it a HG so he told me to look for water under the car in the morning, I told him what was going on, he explain that the Northstar is a low flow engine So it doent push water at a high rate. But he did say this he hates 1st gen Northstar Headbolts. ???????????????

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i got the cooling system check tested, it has a very small leak, the Cadillac tech says he doesnt think it a HG so he told me to look for water under the car in the morning, I told him what was going on, he explain that the Northstar is a low flow engine So it doent push water at a high rate. But he did say this he hates 1st gen Northstar Headbolts. ???????????????

Ignore him, it has nothing to do with the head bolts, some people talk to hear themselves talk

He is also wrong with the low flow cooling system, someone here has the stats

Did he mention that it has a massive radiator for a 281 cu in engine?

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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i got the cooling system check tested, it has a very small leak, the Cadillac tech says he doesnt think it a HG so he told me to look for water under the car in the morning, I told him what was going on, he explain that the Northstar is a low flow engine So it doent push water at a high rate. But he did say this he hates 1st gen Northstar Headbolts. ???????????????

The "tech" found a leak somewhere in the system but didn't locate it? Wow - $100 per hour doesn't buy much these days at the stealership...

The water pump on the Northstar enginge pumps 105 gallons per minute - I wonder what the "tech" considers a high-flow engine???

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

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Thanks Kevin for posting the cooling system pumping capacity

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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105 GPM at what RPM? Redline? If so, that would put it at about 18 GPM at 1000 RPM. I recall the old Guru saying that the water pump turns at the same RPM as the engine.

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the 105 GPM figure was from the guru. I can't remember the RPM it was spec'd but I'd have to guess that was a max pumping volume (redline).

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

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you guys kick butt. thanks for the input , so the cadiilac tech is full of it. i guess this weekend ill take the air purgeline off to check for a good flow. anything else i need to do? by the way how can you tell if you have a bad MAF sensor?

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Kevin, I think he said that the 105 GPM flow rate was at redline.

Dasali, You don't need, and may not have "good flow", just be sure you have flow. It will increase with RPM and may be slow at idle. A bad MAF sensor will let you know with an SES light and a DTC.

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guess what guys i found oil and water mixed under my oil cap, but there isnt any mixer in the oil, now my service engine soon light keeps blinking. and also i saw some water coming from the bottom of my car,and at start up it takes about 5 seconds to start,plus i smell gas as well, (its running but rough) its still strong and gaines speed pretty fast. so this friday im going to get the oil change and see whar happens next, any suggestions on what i should do next after the oil charge.....

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Explain this, what do you mean by mixer?

"i found oil and water mixed under my oil cap, but there isnt any mixer in the oil"

If the service engine light is blinking codes are being set, my guess its a P300, check your codes...

Next you should check to see if you breeched a head gaskets, either have a radiator shop with a tester check it or use the NAPA test kit

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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You can send your oil into BLACKSTONE for analysis to see if you have coolant in it next time you change it

http://www.blackstone-labs.com/

I would test your coolant in the meantime

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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i ment to say there is no oil mixing in the oil pan, the oil looks fine.

Northstars rarely ever put coolant in the oil when a head gasket fails. Don't use that as a sign that they are good.

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