Hello All,

Hoping you all could help me... So far this forum has been really great in helping me with getting my 95 LT1 running right. Now, I'm working on the cooling system. I'm almost certain the cooling system was modified because the techs couldn't figure out how to keep the temp down. Upon start, the fan immediately turns on and stays on the entire time the car is running and I also noticed the Engine Coolant Temp Sensor was intentionally left unplugged (zip tied). Also, I always get a strong coolant smell after more than 30 minutes of driving and the temperature gauge is always around 180-200. It's probably been like this for the past 4-5 years...

I would like to get the cooling system right...any advice?

Thanks!
Jerome

 

My temps after warm up stick between 195 and 205. The coolant smell indicates a leak. Very possible that its a heater core if you smell coolant inside and have no leaks outside.

Have you tried plugging in the coolant temp sensor?

 

I haven't tried connecting the harness back in yet, I'll give it a try... Just checking if anyone has seen this modification yet. Thanks for the info on the heater core...I'll take a look at that as well.

 

If your A/C is on, your fans will turn on. Don't know if that's so at cold start but it is so after warm-up. Here in Florida, I sometimes turn the A/C on to keep the engine cooler in traffic, even when I don't need A/C in the cabin.

If the Temperature Sensor (at the water pump) is disconnected and zip-tied off, the previous owner probably has the fan relay jumped or switched. Check the fan relay for any tampering and... you may also want to check under the dash for a toggle switch.

My LT1 hovers around 197° when moving and 200°-210° when stopped or in slow traffic.

 

No switch, but I'll look around for tampering at the fan relay.

 

..... techs couldn't figure out how to keep the temp down. Your temps (180-200) are perfect. Your techs are rookies.

Upon start, the fan immediately turns on and stays on the entire time the car is running. If there are certain trouble codes set, the fan will run continually.

I noticed the Engine Coolant Temp Sensor was intentionally left unplugged (zip tied). There are 2 coolant temp sensors... 1 in the water pump (digital - interfaces with the EMC).... 1 in the passenger side head (analog - sensor/sender - interfaces with the gage).


I always get a strong coolant smell after more than 30 minutes of driving and the temperature gauge is always around 180-200.
Either you are leaking coolant from the heater core, or from the overflow bottle due to expanded coolant not returning to the rad via a siphon. How ofter do you have to add coolant?

I would like to get the cooling system right...any advice?
At 180-200, your temps are perfect.



If the digital gage is incorrect, and the engine is truly overheating, you need to check air flow and coolant flow. Since your fans are always running, there is no problem with air flow. To check coolant flow, remove the t-stat, and check to see if it opens when you place it in boiling water..... replace it if it doesn't open fully.

You need to start out with a full cooling system, and the overflow bottle at the correct level when 'cold'. As the engine heats, expanded coolant should flow to the overflow bottle, and return to the rad via a siphon during cool-down. If the level in the overflow doesn't lower during cool-down, there is a breach in the closed-system.... check hose clamps for tightness, check hose ends for splits, check the rad cap gasket for any deformity, anything that will allow air to enter.

If the head gasket was ruptured allowing exhaust gases to enter the cooling system, the temps would rise rapidly, the overflow bottle would overflow with expanded coolant, and no siphon would occur.

 

Seabright, thanks for the reply and advice...

The trouble code I get is H15 and H32. I assume H15 is due to my cooling modifications or the Engine Coolant Temp Sensor (water pump) is not connected to the wiring harness. I did check the fan relay harness and it does look modified because there are two wires grounded together and lots of electrical tape. I'll probably map it out this weekend with the FSM. I'll also troubleshoot the thermostat as you suggested and also monitor the overflow bottle. I did have to put some coolant in not too long ago. Thanks again and I'll report back what I've found.

 

BTW, my H32 code... I'm not sure yet if I have to replace the EGR, but I do know that I have leaky injector(s). My oil dip stick smells like gas and measurement is above the max line...also, fuel pressure is about 38 and steadily drops... I just received the injectors from FIC so I'll try and replace this weekend.

 

How did you get the 180-200 temp reading, if the digital temp
sensor is not connected?

 

That was just a good guess based on my analog gauge...180 because it sometimes dips below the 185 mark.

 

Just for your information; on my 95 both fans run at the same time on either High or low. On earlier year vettes they operate differently.. so on your vette they Should run together.

Mine come on low speed when the A/C is turned on, or if the Digital gauge exceeds 228°f They come on at High speed when the A/C Condenser internal pressure exceeds [xxx] and or if the Digital gauge exceeds [xxx] I don't remember the x values.

I would not be surprised if your fans are running do to a stored PCM code. The ECT probe is an important PCM input so you need to address this issue before fussing with the fans.

 

A code will be set with the digital sensor (water pump) not connected.
The analog sensor/sender will not set a code if disconnected.

The digital sensor needs to be connected for the vette to run properly.
That is the only source for the engine temp. The analog sensor/sender
just moves the dash gage.

 

I might be wrong on this but doesn't the ECM need the digital temp to come out of open loop? It doesn't look at the O2 sensors until a certain point/temp and then goes into closed loop. The system engages the fans by grounding one side of the relays. If you see grounds taped into the relays that is why they run all the time. Get that temp sensor back into the system, the relays straightened out, and go from there. If there is a problem you need to fix it to work the right way after you get the sensor in. Also take a flashlight and look in the opening on the passenger side of the radiator cover. There may be a bunch of junk in between the A/C heat exchanger and the radiator. Clean this out the best you can. Its the number one problem with cooling these car. I've had plastic bags, paper cups, and tons of leaves in this area. You swear these are vacuum cleaners not sports car.

 

Thanks for the advice and info klyde, I appreciate it!
Jerome

 

Thanks for the advice and info Klyde, I appreciate it!

 

You are exactly right on the temperature sensor. If that is disconnected the PCM will make the mixture extremely rich. The engine will start but will be so rich will shake and eventually stall (run like crap in about 10 seconds)

You can also forget about closed loop, open loop and O2 sensors + anything else because the engine will not be in a run-able state all the math computations in the PCM software will be out to lunch. Needless to say the digital temp readout will not be useable.

Just on a weird chance, I would look at the temperature sensor plug to see if someone hung a resistor in there. If they did and got a value in the window of normal operation, the engine would run and the digital temp readout would never change.

 

I think the engine would run. It would simply use a set of stored parameters and make its best effort. It would not run at its best nor would it get good gas mileage. Also over time it would/may destroy the cats do to a rich environment. Once again his best bet is to get that sensor back in and deal with any problems that pop up correctly. These cars also have what's known as limp home mode. In case of major faults the ECM follows a predefined set of parameters in order to get you home so I know that they can run even with major problems.

 

If the fan is staying on all the time it will burn out.

It's not meant to run like that.

 

Sound logical, but I will answer the question in detail. Back in 06 when I first replaced the (first) opti I started the engine with no water pump on to make sure it would run properly before I went any further. Ran good for 5 or 10 seconds and died. Then after a moment (of concern), I realized the sensor needed to be connected to run the engine. So from then I connected the sensor and all is normal, runs smooth and you can test it out with throttle for about 15 or 20 seconds (or so).

But hanging the pump is a pain to make the connection laying it across the air intake. So now I have a selected resistor I plug into the connector, give me about 70* on the digital readout and the engine runs fine with proper A/F ratio which is a neater setup.

The higher the sensor resistance the leaner the mixture. But infinity (open sensor or unplugged) is way out of range and I think the software defaults to a rich mixture. I just remember 7 years ago I thought it was rich probably because of the exhaust. Hard to think that far back with that level of detail.

 

**You are getting some great information here, much much more then most technicians at a typical service center-