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Excess heating

Tiny
ARNOLDLAUSEVICH
  • MEMBER
  • 1990 PONTIAC SUNBIRD
  • 2.0L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 68,000 MILES
New value assembly, lifters, water pump. New thermostat. Still indicates 220 F gradual rise.

Heat reading laser indicates ranges from 160 to 180. Back of value assembly 220 but where therm is located around 160-180.

Does smell oil as running hot and fan never turned on unless I turn on A/C switch.

Replaced thermostat and now running without the therm in place.

Do not know what to do. Remove air in system as I do have a vacuum pump? But it's full of new 50% mix. At wits end.
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Tuesday, July 14th, 2020 AT 9:20 AM

55 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,463 POSTS
First you never want to run any engine without the thermostat as that can cause them to run hotter. This is because the thermostat creates a restriction to hold the coolant in the engine a little longer and transfer the heat.
Then I would probably start looking at the radiator for cold areas, run it and as it warms up check the entire radiator to see if you have any blockages. They will show up as colder spots. I would also test the new thermostat, it wouldn't be the first time a new part was bad. Next would be to verify the temperature, where are you reading the 220 at? Dash gauge? If so the sending unit could be bad and the engine really isn't that hot. Has it actually overheated before or since?
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Tuesday, July 14th, 2020 AT 9:54 AM
Tiny
ARNOLDLAUSEVICH
  • MEMBER
  • 33 POSTS
Thanks Steve for reply. I have a new thermostat to put in. While the radiator was replaced a few years ago and looks great with no leaks. I will try to check for cold spots. Also would the radiator hoses reflect any difference in heat? They both run hot in and out of radiator.

The high read is from the dash, the readings I took were from my hand laser therm.
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Tuesday, July 14th, 2020 AT 10:01 AM
Tiny
ARNOLDLAUSEVICH
  • MEMBER
  • 33 POSTS
Replaced new thermostat. Heat from radiator ranges 230 to 260+. I do not find any cold spots but one strange thing. As I turned off the car "Red Engine Light" on dash. Checking the radiator the temperature went down to 90 to 120 degree range almost instantly. Does this indicate a blockage? By the way, the last time the radiator was changed was in 2006.
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Tuesday, July 14th, 2020 AT 10:19 AM
Tiny
ARNOLDLAUSEVICH
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  • 33 POSTS
Heater core was also replaced a few months ago. Sprang a leak. Forgot to mention.
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Tuesday, July 14th, 2020 AT 10:25 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,463 POSTS
Normally the radiator hoses will be close enough to the same temperature you wouldn't feel much difference at running temperature. You said the fan doesn't come on? That could be the cause of it running hot if it doesn't work. For that I would look at the temperature sensor as you said it does turn on with the A/C, That means the power, relay and the rest works. It just may be that the coolant temperature sender is faulty, the resistance numbers for testing are in the diagram. You could test that by grounding pin B in the test connector under the dash. If you ground that and the temperature comes back down to normal then the fan isn't doing it's job.
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Tuesday, July 14th, 2020 AT 11:37 AM
Tiny
ARNOLDLAUSEVICH
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  • 33 POSTS
Thanks Steve for update.
Sender was replaced so I do not think that's the issue. I will check your recommended diagnostics. Maybe I should just replace that radiator? Would that seem to be the weak link in the lack of cooling? This inspite of not finding a "cool spot"?
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Tuesday, July 14th, 2020 AT 4:06 PM
Tiny
ARNOLDLAUSEVICH
  • MEMBER
  • 33 POSTS
Going back to define cool spot on radiator. A good portion of the right side stays about 260F while a bottom portion indicates 390 to 400 F . Is this a normal heat distribution?
Thanks so much for your continued help. My sensor harness by the way indicates 12V to the connector. Looking at the diagram you attached it indicates 5V?
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Tuesday, July 14th, 2020 AT 4:24 PM
Tiny
STEVE W.
  • MECHANIC
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There should be two sensors if I recall. One is for the fan control and one for the gauge.
Heat wise it sounds like that radiator has an issue. However there shouldn't be any coolant that hot either. You may want to do a head gasket test just to be sure you don't have an issue there.
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Tuesday, July 14th, 2020 AT 4:29 PM
Tiny
ARNOLDLAUSEVICH
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  • 33 POSTS
Head gasket replaced. Was blown when I did. I think I will replace that rad. That based on what temp distribution I indicated to you. Some where I read that the top temperature should be hotter than the bottom. Well that's the reverse here. What ya think?
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Tuesday, July 14th, 2020 AT 5:20 PM
Tiny
STEVE W.
  • MECHANIC
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Your call on that. I would get the fan working as well. Then go from there.
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Tuesday, July 14th, 2020 AT 5:57 PM
Tiny
ARNOLDLAUSEVICH
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Thanks Steve.
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Tuesday, July 14th, 2020 AT 6:26 PM
Tiny
ARNOLDLAUSEVICH
  • MEMBER
  • 33 POSTS
Sensor for the fan control don't know where this is located. I only know the one on the valve cylinder location. Also I ordered another fan relay, but guess according to the schematic you sent its located near the ECM?
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Wednesday, July 15th, 2020 AT 7:24 AM
Tiny
STEVE W.
  • MECHANIC
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The relay is in the power center under the hood.
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Wednesday, July 15th, 2020 AT 8:27 AM
Tiny
ARNOLDLAUSEVICH
  • MEMBER
  • 33 POSTS
Steve, I had a brain fart.. Experimented with turning the A/C on, this activated the fan. I would expect the temperature not to climb with the fan on but it still did. Again, I think it's pointing to the radiator. I did find the power center so I will replace that relay also.

Thanks so much for your advice and help.
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Wednesday, July 15th, 2020 AT 9:37 AM
Tiny
STEVE W.
  • MECHANIC
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With the fan on and temperature still going up I would say you have an issue. I would still do a combustion gas test though, just to rule out something like a cracked block or a defective gasket. If you start with a cold engine and then watch the temperature at idle, how long does it take to get hot? Another test would be to get a cooling system pressure tester and just put the pressure gauge on when you start the engine cold. The gauge shouldn't move at all until the engine has run a few minutes and even then it shouldn't get over 15 psi. Any higher and you have a problem, especially if the pressure starts rising as soon as you start the engine.
This says for head gaskets but it is the same testing for any combustion leak, be it a gasket, cracked block or head or some other odd item.
https://www.2carpros.com/articles/head-gasket-blown-test
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Wednesday, July 15th, 2020 AT 10:16 AM
Tiny
ARNOLDLAUSEVICH
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I had the same temperature issue before I replaced the upper half of the engine. This is the valves rebuilt and a new cam with lifters. All gaskets are new. Nothing was done below this point so if I have an issue it would be piston block related and I doubt this is happening. (?)

I do have a pressure tester and will try that also.
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Wednesday, July 15th, 2020 AT 10:48 AM
Tiny
STEVE W.
  • MECHANIC
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Okay, in that case I would still do the pressure test just as a precaution. If it tests good then great. As you said that turning the fan on didn't lower the temperature there is a problem. Either coolant flow or that the heat isn't transferring. Partially blocked radiator or a bad radiator hose could cause that.
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Wednesday, July 15th, 2020 AT 1:12 PM
Tiny
ARNOLDLAUSEVICH
  • MEMBER
  • 33 POSTS
I found my block-check kit and will try it tomorrow. The relay will come soon and there are 3 in a row. I need to know which one is for the fan. The schematic you sent me should indicate the position? Cannot find solution on internet. The closest one is for a Fiero where 3 relays are in a row. I cannot find markings on the panel itself, but will investigate further as it maybe covered in dirt and grease?
Thanks again Steve.
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Wednesday, July 15th, 2020 AT 5:28 PM
Tiny
STEVE W.
  • MECHANIC
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The cooling fan relay is mounted above the brake master cylinder on the firewall.
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Wednesday, July 15th, 2020 AT 9:06 PM
Tiny
ARNOLDLAUSEVICH
  • MEMBER
  • 33 POSTS
Got it, thanks.
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Wednesday, July 15th, 2020 AT 9:27 PM

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