XTwinTurbo

Anyone know why I have two different coolant temperatures displayed on my C4 cluster? 1994 LT1 C4 that is showing normal (170 degree) temps on the digital display but then close to over heat coolant temp on the analog display gauge.

Which one is correct? Are there two sensors and one has gone bad?

eschoendorff

IIRC, there are two different sensors. The digital readout comes from the sensor at the bottom of the water pump (I forget where the other sensor is). I always go by what the digital readout says.

John A. Marker

I would question the 170 temp, seems LOW for these cars. Should be another 20 degrees higher if your warmed up and driving.

RollaMo-LT4

As mentioned, there are two sensors.
But even if both are 100% accurate, you will always have two different temps displayed.

Usually, the digital gauge is the one to go by.
That analog gauge does not have a linear scale, so it is next to impossible to tell what the actual temp listing is.






I guess it would depend on when the 170 was being displayed?

Once up to operating temps, and moving down the road at any speed over 45mph, that digital temp gauge should be in the 190°F - 198°F range.

When the digital temp gauge gets up to approx. 228° (where the cooling fans come on), that analog gauge needle will be very close (but not quite into) the shaded area at the upper limit on the dial.

don hall

Well written....

As posted, the digital temp gage is in the water pump ('talks' to the ECM - 2 wire), the analog temp gage is in the block between #6 & #8 cylinders (only moves the needle on the analog gage - doesn't 'talk' to anybody - 1 wire).

If changing the analog sensor/sender (some stores list it as a sender, not sensor), no need to worry about the minimal loss of coolant. Just add the 12 oz +/- (?) to refill.

XTwinTurbo

Thanks for the response and suggestions. The low digital temp reading is expected since I'm running a low temp thermostat and tuned my fans to come on early. Looks like the analog sensor may need replacing but will first check that I'm not simply low on coolant

Scootin_Z

So guys, Doing a search and found this thread. To make a very long story short, New Golen engine and pro charger. Fans on at 175 and 165 stat. I am reading these cars run warm. Talking to Chad Golen, (been a while now so I can't remember the numbers) but the numbers he rattled off seemed high to me as far as operating temps and what is to hot and shut it down. Now any car will overheat at 260 as thats all the coolant will handle before boil correct? So that said, what are NORMAL operating temps, and are these cars prone to overheat in traffic? (Stock, not my set up) I want to know what is "normal" for these cars as far as operating temps. I have a mechanic buddy telling me at 240 your really pushing it (and I agree) but looking in the service manual under flushing the system, it is saying the stock don't open until 200??? Why so hot???

Thanks guys!

don hall

This is good LT1 cooling info....notice when the fans activate, and the reasons for running at higher temps:

http://www.fierolt1.com/lt1_cool.htm

Scootin_Z

Seabright, I just finished reading your article. (found it in another thread...nice job BTW) so I guess 230 is "ok" for these cars? Man that just seems too high to me. I can't believe how high the fans come on at! What is too high for these cars? I am taking this thing on Power Tour next week and the south can be HOT!
Also I read at the end of your article about the fans. I had the car tuned and I had him turn the fans on at 185 and now I am thinking that's too low. I did have to put an alternator in it last year so I am wondering since I am running them a lot that is a problem. I also wonder if mine shut off after the 45 mph. Although if I am doing 30 or above she runs a cool 173 on the dot. In traffic she likes to climb though!

Scootin_Z

And when I say 230, not operating, but if I hit it in traffic. I still think I would be pulling it over until I can roll 30 or above to keep cool

don hall

Check with your tuner, but if the fans activate below
228, they will be 'on' all the time.... not good.

The primary fan does a good job of controlling temp. Have never had the secondary fans activate. Definitely have the fan activation raised to 220, or normal - 228.

I'm no tuner, so if raising the temp for fan activation
causes concern with your tuner, listen to him. Maybe he should be acquainted with the LT1 cooling article.

Scootin_Z

Well to be clear, it was more of a hey we can do it so why not decision. I have had this car on and off the road over the past 3 years or so and it just seemed to run hot when we first got it on the road but now I am learning they are hot by nature. My thinking is if I have them come on right when she started to climb (in traffic getting in and out of venues on power tour can be a nightmare) I thought it would buy me more time before I have to shut down and let it cool. What temp would you be shutting your LT1 off at Seabright?

don hall

You should not have to worry about air with both fans activated, unless the air flow is blocked with debris.

Check for debris clogging the radiator. If you haven't flushed the cooling system, I highly recommend it.

Flushing includes removing the knock sensors from the bottom of the block, and squirting water into the knock sensor holes several flushes. That is the sump of the block, and sediment can really build up.

Scootin_Z

Thats what brought me here. I just did a major flush yesterday and today. Motor is pretty fresh, but I don't know if there was some old crap in the system or what (New Rad with motor too) but it was nasty. I am stumped on how it got so bad. Maybe sitting? I have it crystal clean after 3 flushes. (yes pulled the sensors and flushed the HC) I'm going to see what it looks like again after Power Tour and maybe dump it one more time.

don hall

You should never be concerned with shutting down your vette with a functional cooling system. This means: clean coolant flow, clean air flow, operational t-stat. A functioning cooling system includes no coolant loss..... closed system (expanded coolant overflowing to bottle, and siphoning back to reservoir during cool-down.

If the siphon is operational (bottle level is reduced, and the reservoir replenished) during cool-down, that is good. If the siphon is not working, there is a breach in the closed system.... hose ends split, cap gasket deformed or split, any avenue that allows air to enter the system...must be repaired.

Scootin_Z

Well yeah in a stock format yes, but remember there supercharger on this car. I did a leak test and it held pressure just fine. BUT that does not test the cap as that's where the pump is hooked up. I will so how it behaves after this flush.

don hall

Supercharger cooling is above my pay grade.
I'm going to quit professing my cooling intellect,
and see what others have to suggest.

Scootin_Z

LOL, well thanks for all your input Seabright