Results 1 to 10 of 17
12-30-2009, 09:15 PM #1
1989 suburban coolant temp fluctuation
This is driving me crazy. After sitting outside one really cold night, my truck coolant guage started really acting strange.
It moves around over a 20 degree temp range back and forth slowly while I drive. Doesn't seem to correlate to any driving type...like it isn't everytime I stop it rises or anything, it just seems to happen steadily whether I'm in stop and go traffic or whether I'm crusing at a constant speed.
It just slowly climbs..just to the point to make me scared, the slowly goes back down and repeats very slowly.
The engine is freshly rebuilt with 2000 miles on the rebuild. Cooling system is entirely new at the time of rebuild including gauge sending unit.
I swapped the thermostat and it had no effect. Anybody every experienced anything like this?
12-30-2009, 10:55 PM #22011 Chevy Silverado 3500HD, Dmax/Allison, Taupe Gray Metallic, Line-x over the Rail & Rockers, S&B Intake, Banks Monster Exhaust, Rigid Dually D2's, Cognito Leveling Kit, Cognito Steering Braces plus much more.
"Suburban" There is no Substitute.:great:
SOLD - My Loaded up 02 2500 Suburban.
12-30-2009, 11:03 PM #3
The big question is: Is it running hot? Despite what the gauge says check the temp with a thermometer. I use a digital thermometer, but an analog kitchen type will do.
An engine that is overheating can lose coolant and the temp sensor will not have any coolant to measure. Check to make sure you are not losing coolant. Also make sure you don't have any air in the system.
If the truck is running in a reasonable temp range, its probably just a bad temp sensor.There is no way to happiness....happiness is the way.:yipi:
High Desert SoCal
93 K1500 burb (personal) 350 AT 3" Lift 250K+
02 Honda Civic LX
Looking for a 1990's Miata for an engine swap
12-31-2009, 07:15 AM #4
When I swapped in a new t-state I put in a 180. It used to be 195.
How do you take the temperature with a thermometer? Where do you have access to the coolant? Has anybody ever used one of those laser non-contact thermometers?
I would really like to do this becuase I could eliminate both bad temp sender and bad gauge. But I can't quite picture where I would stick a thermometer to get an accurate coolant temp reading? Please Advise!
Last edited by Big6ft6; 12-31-2009 at 07:21 AM.
12-31-2009, 07:49 AM #5
- Join Date
- Feb 2008
- South Florida
Don't forget your mechanical fan. You mentioned it happens when you idle or drive at a slow constant speed. Once the vehicle is travelling at 35MPG or more you get plenty of air from the grill. If that is the original fan check it out!1999 K1500
3 angle valve job
Everything else stock
Nice and clean!
12-31-2009, 07:51 AM #6
Sounds like the fan clutch to me !!!! And yes ,the laser things work, just point it at the thermostat housing !!!!
1996 Suburban K3500 SLT DUALLY
1988 Camaro RS 383 stroker LT1
1992 32' Aero-tek Race Boat, 600 CI BBC
WE CAN STICK A DIESEL IN ANYTHING
SPECIALIZED IN CUSTOM CONVERSIONS OF ANY KIND
12-31-2009, 11:39 AM #7
Hey guys yes this is the original mechanical fan, however the temperature fluctuations happen at all speeds, even highway speeds.
I'm assuming my fan clutch is o.k. becuase it feels like a hurricane under my hood when the truck is parked and idling. It is also 15 degrees outside here in Wisconsin so I don't feel like the engine temp has any excuse to be climbing!
Thanks for the ideas, I think I'll get a laser thermometer at harbor freight and see what I learn.
One thing I'm wondering, would a head gasket problem cause wierd temperature swings if products of combustion were bubbling into the coolant jacket? when I bought the engine the last owner had a buddy bolt on the heads. (supposedly a local race car mechanic) I just trusted they were bolted on correctly.
This morning on the way to work the truck warmed up normal, up to 180, paused, then continued to climb to 210, then seemed to stabilize around 210 moving just a little below and back up to 210.
I'm completely guessing on these temperatures too, becuase the factory gauge has only 3 numbered positions.
The left most position is 100, then 12-noon on the gauge reads 210, then the third position is 260.
What's wierd is the 210 mark on the gague is the same distance from both the 100 mark and the 260 mark so clearly the gauge isn't labeled inearly becaues 100 is 110 degrees from 210 and 260 is only 50 degrees from 210but on the gauge they are equal distances apart ....wierd.
I should get an aftermarket gauge and see how accurate this factory gauge is.
12-31-2009, 01:18 PM #8
- Join Date
- Oct 2009
- Elmhurst IL
When my head gaskets went my temp gauge would bounce and do the same thing but if the motor is new that shouldn't be a problem.1988 GMC Sierra Classic 3500 Dually.
12-31-2009, 02:20 PM #9
- Join Date
- Feb 2007
- Blog Entries
1991 Chevy Suburban 1/2 ton 2WD w/ chevy SBC 350-3/4 ton drivetrain upgrade w/4.10 gears 199K miles
2005 Saturn ION-2 Stock 255K miles
1982 Bronco, 1993 Bronco (sold), 1971 M35A2 Deuce and a Half
There are 10 kinds of people, those who understand binary, and those who dont...
Remember kids, the only difference between screwing around and science is writing it down- Adam Savage
12-31-2009, 04:44 PM #10
What are the chances this is purely a funciton of the super cold temperatures? Is it possible that when I first turn on the engine once the coolant hits 180 the terhmostat opens and really cold water rushes into the engine and makes the t-stat close again?? But now the coolant temp rises more quickly before the t-stat has a chance to fully open so I get spike on the temp gauge? then the t-stat opens cold water rushes in and it repeats?
I don't know...it still seems the coolant temp should never go above my t-stat temp. I pray that this is either a funky gauge issue or a funky sending unit.
If this is a head gasket I'm going to die....what about a bad water pump? Not long ago I pulled the radiator cap off and could see a good stream of coolant coming from the heater core return hose. It seemed a pretty strong stream, so I assumed the water pump was fine, but maybe it is weak? I just bought a cheap one when I put the engine in.
Last edited by Big6ft6; 12-31-2009 at 04:54 PM.
By engineerbrian in forum General Chevy & GM Tech QuestionsReplies: 3Last Post: 07-15-2010, 04:06 PM
By Googenheimer in forum General Chevy & GM Tech QuestionsReplies: 3Last Post: 02-22-2010, 11:50 AM
By thekingsphance in forum GM PowertrainReplies: 3Last Post: 08-12-2009, 10:20 PM
By L0sts0ul in forum Chevy Suburban Forum (GMC Yukon XL)Replies: 11Last Post: 08-03-2009, 12:19 AM
By kbarrett in forum Chevy Suburban Forum (GMC Yukon XL)Replies: 1Last Post: 07-16-2007, 09:10 PM
Tags for this Thread