wickedlysmiling1

I have a 1998 Pontiac T/A, Original LS1 6Speed. I've been doing some preventive Maintenance over the last few weeks. I've replaced the Alt., P/S pump and bulbs. After replacing the P/S pump I noticed the car starts to get hot at idle. It has never reached the a temp over 230. Keeping with the theme of preventive maintenance I started looking at relays and fuses. Changed them all out. I also changed the coolant temp sensor and pigtail. When cruising the temp stays constant and doesn't get hot. While idling with the a/c off it gets hot quicker but with the a/c on I've noticed that the low speed cooling fan is a constant on. What I've been able to come up with at this point is the high speed fan does not come on. To test this I unplugged the pigtail from the coolant temp sensor and the high speed fan kicks on hard and continues to run. I ordered a new sensor today and have yet to install it. I know the pump is good as well as the t-stat. There is no boil over and no exhaust entering the coolant passages via a test kit from oreilly. A pressure test confirms that my system has no leaks but to go one step further I also did a leak down test and its fine. While I am waiting for my new sensor I thought I might be overlooking something.

Any suggestions or anything I have overlooked?

LS6427

iTrader: (2)

If the fans are not working in HIGH speed.....you will overheat when the car is not moving.

BOTH fans should always run together on LOW and HIGH speeds......one fan should never run without the other.

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RPM WS6

iTrader: (3)

You talk about it being "hot" at idle, but you didn't define "hot".

Understand that with stock fan settings, the low speed fans will not engage until 227°F with the A/C OFF. So if it's not exceeding 227°F, then you're not going to see any fan action at all with the A/C off and stock tuning. Also, keep in mind that the high speed fans are not set to engage until 235°F with stock tuning, and therefore would almost never be on at idle unless the engine had heatsoaked to a high enough temp after shutdown to then call for engagement after a quick restart.

The stock t-stat is an 86°C (187°F) unit, so when moving at steady speed in cool weather you should eventually see coolant temps drop into the 19x°F range on a scanner.

Sounds like you might be chasing a problem that doesn't exist.

johngrn

I also own a 98 TA LS1 and having a simular problem and have tried all the thing you have done and the only thing left is to replace the radiator,last test I did was to start the car cold with the radiator cap off when it get up to running temperature feel the hose that comes out of the thermostat housing and feel it as it goes down and see if it temperature is consistent all the way down if it is cooler at the bottom there is a good chance that your radiator is is blocked, also when replacing any parts its best to buy GM -AcDelco parts you get what you pay for but you do not have to buy them at the dealer check at Rock auto or amazon,let me know if you got it fixed???

LS6427

iTrader: (2)

Radiators can't really get blocked...unless you stuff a rag into it. Or its literally 30 years old and has sludge inside it. But in that case there would have been signs over gradual overheating for years and years before it was totally blocked.

Anyone with an overheating problem that they cannot figure out....they need to take the tstat out, mount the tstat housing back up......top it off with coolant/water. Then with the radiator cap off start the engine and see if the coolant IMMEDIATELY starts to flow. If it does.....there is no blockage anywhere....and the water pump is actually pumping and does have the very RARE possibility of a sheared shaft. In this case.....get a new tstat.

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d1bell

The thermostat and housing are integral parts on the 1998 LS1. I found this out when replacing mine today.

psychosid30

iTrader: (7)

The thermostat and housing is sold as one unit, but, you can remove the internal section to perform the check LS6427 is talking about. You just have to press the crossbar section of the thermostat down about 1/4" and spin it until it clears the two tabs securing it to the housing.

johngrn

I also a stock 98 TA with the same problem and has take me many year to figure out what is going on, the temp of 220 is a factory setting the way it works is at driving speed the temp come down to about 212f the when in traffic or running below 30 mph it will go up to 220f + this is made to work with the catalytic converter to keep emission under control, Now if you want to fix this problem there are two things that must be done get 160 thermostat ( I bought mine at oreillys) and you have to have the fans settings reprogramed, on this car the 160 thermostat controls the lower end temp @160 and the FAN SETTING controls the high end setting @ the 212f and the 220f

RPM WS6

iTrader: (3)

As mentioned above ~5 years ago, this is not an actual "problem" (i.e. nothing is broken, it's operating in the temp range intended by the factory). But yes, you can certainly reduce temps by making changes to fan tuning and, further, the t-stat. However, you do not need to change the t-stat to get lower running temps (to a point), you can simply reprogram the fans. The stock t-stat is a 187°F unit, and will allow running temps in the mid-low 190s at steady cruise or at idle with proper fan settings. If you want to go lower than that, then yes, you would need a lower temp t-stat.

I posted the factory fan cut-on temp settings earlier in this thread for reference (neither "212" nor "220" are actual setpoints from the factory).

01Z0H6

iTrader: (63)

I too recently had the same issue with my 96 Z28 (LT1). I did everything you did... drained, replaced coolant, new T stat (stock AC Delco), coolant temp sensor (WP), new relays x 3... Driving it would run cool, once stopped and idling temp would climb fast... My fix was the SLP fan switch... works like a charm... high/low switch turns the fans on w a click of the toggle... BOTH fans work as they should, car never exceeds 190-200 deg... Haven't even had to turn on high... Keep the fans on low... Summer is coming though. Next is to go through the AC system as it is blowing warm and the compressor is "trying" to engage. Thinking it is out of Freon....

RPM WS6

iTrader: (3)

I think this old thread has become entangled with three separate issues. The OP (back in 2014) seemed to assume that something was wrong because he was only seeing low speed fan operation at temps below 230°F. This is proper with stock tuning for an LS1 because, again, high speed won't activate until 235°F (even low speed doesn't activate until 227°F with the A/C off).

Then, two days ago a different member bumped this thread to indicate how one could attain cooler running temps by installing a lower temp t-stat and reprogramming the fans. His method is in fact proper for maintaining lower temps, but the implication that this is a "fix" for something was NOT correct because, again, the factory tuning actually specifies those high fan cut-on temps in the first place (i.e. nothing is actually broken, therefore this is a modification rather than a "fix/repair").

Lastly, 01Z0H6 seemed to have an issue where the fans weren't activating at high or low speed at any temp, and that would obviously be an actual problem which is different from the other posters above.

I don't know the factory fan setpoints for a '96 LT1 car offhand, but the folks responding with LS1 cars are chasing a "problem" that doesn't exist if they're looking for high speed fan activation below 235°F with stock tuning.

01Z0H6

iTrader: (63)

MY mistake... Only sharing info from when the one guy bumped the thread.

99 Black Bird T/A

iTrader: (4)

RPM is correct about the factory fan settings and folks thinking there's a problem when it's just the stock programming.

Will add this in general as it applies "higher than expected temperatures" with 3rd & 4th Gen Camaro's and Firebird's. Probably applies to a lot of other other cars too.

Keep the area between the AC condenser and radiator clean.

When doing maintenance, check and clean out the area between the back of the AC condenser and the front of the radiator.

I've found various types of road debris in the area a couple of times. Leaves, twigs, plastic bags, cups, home insulation etc. This can obstruct airflow though. The AC will be less effective and the car will run hotter.
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