SoupyDamit

Hi All

So…. I was driving in from Oakbrook inbound in stop and go traffic (mostly stop) when my 1994 Corvette started to overhead with steam coming out the right handside. The air-conditioning was always off – it was a cool day.

The analog engine temp would hit 260+ (analog engine temp sensor on the right hand side of the engine block). I would guess by looking at the gauge that it might have hit 290.

And the digital engine temp would display less - it always fluctuated between 210 and 230 (digital engine temp sensor is on the front of the engine temp next to the water pump) – it never got as hot at the analog.

The oil temperature gauges (digital and analog) where always around 180 or so - In the normal range.

I could hear at least one of the two cooling fans kick on when the digital temperature would get above 217ish. There were no warning lights. The engine ran smoothly – just with steam coming out the right hand side.

I have removed debris from the front a couple month ago.

Also there was previous work done on where the distributor (Opti), water pump and thermostat where replaced on 11-24-2010.

Can you guys give me any ideas?

Thanks

TWISTERUP

I'd start with a visual check for leaks --hoses etc. If nothing is found --then have the system pressure checked.

STL94LT1

Possibly a bad radiator/surge tank cap, it may not be holding pressure.

c4cruiser

The digital gauge will be more accurate than the analog gauge. The analog gauge is not linear in that as the needle moves toward the higher numbers, the numbers are closer together.

210-230 as displayed on the digital gauge is about normal for coolant temps with LT1's. The "steam" is not The primary fan comes on at around 226 degrees and will turn off once coolant temps drop 41 degrees. The secondary fan will come on at 238 and turn off after a 41 degree drop.

Also, both fans will run when the A/C is turned on.

Definitely check the pressure cap and replace if needed. It would be a good idea to do a pressure check on the system. AutoZone stores have pressure testing equipment you can rent at no cost and the equipment will also test the cap.

It's possible you may have a leak in a hose or a loose hose clamp. Also look for coolant drips on the underside of the surge tank (with the pressure cap. Could be a crack or a leak where the hoses attach.

FireRoc

Depending on how long ago (if ever) the Dexcool was changed it could be that radiator is plugged with sludge (from the Dexcool). I had this happen to a '98 Trans Am where it wouldn't cool properly. I could only go 60 mph with the fans on full (SLP manual override) and heater on full (not pleasant in the middle of the summer). I wound up replacing the radiator as the bottom third was plugged solid.

SoupyDamit

I will keep you updated - I dropped it off at the shop. I am really hopeful that I didn't damage the engine and its something something simple.

I find it really odd that the 2 temperatures gauges where so different.

desertmike1

Not odd at all...combustion gas's build up in the "head" cooling Passages.
This is why the head temps act erratic, or really hot.

SoupyDamit

Yea - I am seeing items in the forums about having to 'Burb' the cooling system in order to get air pockets out of the high points of the engine. I am thinking that there was an air pocket when they installed the opti and water pump.

I didn't drive it in the winter months to know whether or not it was running correctly.

Man..... you would think that this car was a 1 year old.... all that burbing and stuff you have to do to get it to behave.

SoupyDamit

http://forums.corvetteforum.com/pict...ictureid=78016

Here is the picture of her...

desertmike1

Very nice.......

pcolt94

Hells bells a picture of my car……Darn good looking also.

A few corrections from above posts. Dex-cool is not the coolant in the 94, it is the standard green coolant.

And only the left cooling fan comes on when the A/C is turned on. The secondary (right side) fan comes on only at 239*. It was not until 95 and 96 models till both fans worked simultaneity on high and low speeds.

purvissp

Your problem sounds exactly like the one I have been trying to figure out for the last few days.

Friday I was driving around with the AC off and notice in slow traffic when I stopped at a stop light the analog gauge would get up in the gray zone near 260 and the fans did not kick on. That start to concern me. I checked the coolant and it was low and looked a little dirty so had had it flushed and refilled, but the car still got hot, by the analog gauge in slow traffic. I finally found out how to display the LCD temp gauge an found the analog gauge was reading 30-40 degrees over the digital.

Today I tried a little test. I parked the car and let it idle with the hood up so that I could see the fans. Sure enough the analog gauge started going up into the gray zone near 260, but the digital was only in the 220's. When the digital gauge hit 228 the fans turned on and cooled the engine back down. I let this cycle run 3 times and all 3 times it did the same.

That analog gauge can not be trusted. The digital one is more accurate and is the one temp that turns the fans on.

Don't think there is a problem with the fans or cooling cycle, but I will run with the digital gauge on for awhile just to be sure.

Don't trust that analog gauge.

proracr

I'm glad that the 94's never used Dexcool as it isn't worth a darn. My '96 Impala SS had that crap in it and it plugged up my heater core.

REDC4CORVETTE

http://www.ecklers.com/corvette-hot-...1992-1996.html
Or the heater core

desertmike1

Why?

This probe is located near the heat source!
How much more accurate can you get.

lt4obsesses

The digital gauge is the more accurate. As explained above, the analogue is not linear so it "looks" hotter. But it is not in actuality.

My first question is, is there any signs of coolant leakage in the engine bay. Steam is caused by one of two things, coolant boiling (overheat) or leaking onto something hot.

I had the same occurance this fall. At a light and saw steam coming out of the front right. There was coolant on that side of the engine bay. All the hoses seemed fine, looked and looked for a week. Then, quite by accident, I noticed, looking thourgh the slot in the radiator shroud, that I had a crack in the radiator tank. The plastic piece on the side of the rad. If you do not have coolant in the engine bay, perhaps your leak is lower down and the coolant is going out the bottom.

I don't know about the 94's but I know my primary fan comes on at 228* and the secondary at 230*. It is not unusual to see 230* in mostly stop and a little go traffic.

SoupyDamit

So I got the car back Friday from the shop. They replaced the pressure relief valve on top of the surge tank, the temp sensor next to the water pump and a couple of clamps. Ran a pressure test and confirmed the fans kicked on.



I tested under similar conditions and no steam - it held to 190 degrees.



I tested on a run down to the quad cities....



Still 192 at 100mph for 20 minutes

You know..... one of the up sides to having a financially irresponsible state government is they lay off all the highway patrol officers first. God bless a America

Thank you for everyone's help.

Soupy

Richard Church

dchildress

Good job. I replaced my Opti, water pump and coolant with Engine Ice and a 160 thermostat last year. Mine was running over 200 at 50mph in 6th and would cool off slightly in 5th & 4th. I pulled the thermostat and found it had some RVT on it that I guess I gooped on when doing the pump and the good lodged in the thermostat. Popped in a 180 (no 160 available and honestly a waste) and it now stays cool all the time.

Macs94

I have never seen or heard of combustion gases in cooling passages. Than doesn't occur unless you have, 1- a cracked head, 2- a blown head gasket, 3- a cracked block....