Cooling System Question

Dmod81 · 04-07-06, 07:45 PM

I have a 91 L-98 and while driving through town (66 degrees outside), I noticed that the temp gauge would go very high. Not sure of the temperature since my guage doesn't have hash marks, but the needle was close to touching the 2 in 260 for anyone that has a temp guage like mine. Still not in the red zone though.

While trying to figure out what was wrong, I noticed that the aux fan never comes on. Even if I turn on the air. Also, I think I have a coolant leak that I cannot find. I can smell coolant on the passenger side of the car with the hood up. I also hear a sound like pressure being released from the passenger side when I shut the car off sometimes. Maybe the cap? The front of the radiator is clean, I just cleaned it today. Still having the problem.

Sorry for the long post, I just have no idea where to start.

Rabbit · 04-07-06, 10:04 PM

The caps a good place to start. Suggest you do a pressure test.

Redbob · 04-24-06, 10:49 AM

You didn't say how many miles you've got, but if it's over 100K, you need to watch for a bad (leaking) waterpump; just replaced mine at 114,000 and found it also needed a new intake gasket - the water passage there was leaking also. Between those two fixes, I think I've got my water leak problem solved.
I'm running a 160 thermostat, as I have for the past 10 years, and the water temperature will stay at ambient plus 85 degrees on a level road at 70 mph.

vetteboy86 · 04-24-06, 12:29 PM

I would say you have cause for alarm. I do not have a guage like that buy if it is getting that high I would be concerned. The cars were engineered to run hot, but I dont think running that hot is normal. The problem that I have read about the analog guages is that in some cases they are not all linear. So if the distance between one tick mark may reperesent a larger variation then the difference in two other tick marks that are the same distance apart. I am not sure if this is true, I never have actually verified it.

Now to your problem. Check that the coolant is flowing, start the car with the cap off and when the thermostat opens, verify that the coolant is moving easily in the radiator. Also make sure the level is up. The water pump is another good place to look. To check that fan, hook it straight up to a 12 Volt supply. You may want to put a 5 to 10 amp fuse inline with the wires. If the fan turns on, then the motor is okay, and then you can look to the relay, or possibly the circuits that control that.

Keep us posted on your progress.
Craig

6speeder · 04-24-06, 01:34 PM

[quote=Dmod81]"I have a 91 L-98 .... I noticed that the aux fan never comes on. Even if I turn on the air. "

That's problem #1.... fix the fan.... sensor, fuse, wiring, etc.

"Also, I think I have a coolant leak that I cannot find. I can smell coolant on the passenger side of the car with the hood up."

Problem #2.... your engine is probably so hot that any trace of a coolant leak is evaporting. Have the cooling system pressure tested.

"I also hear a sound like pressure being released from the passenger side when I shut the car off sometimes."

When you shut the car down, the temp will rise for a short time due to the lack of circulation and cooling. The hiss you hear is the release of expanded coolant and pressure. This is normal. That is why you have an overflow reservoir.

"Maybe the cap?"

If the overflow reservoir is at full when hot, and on low when cold, the cap is working. Check to ensure that the reservoir is low when the engine is cold, and that the radiator is full. This will tell you that coolant is being syphoned back into the system. If the cooling system has a leak, a syphon will not occur, and the system will be low on coolant when you start.

"The front of the radiator is clean....."

That's good. Your problem is with the fan not working. You only mention that the temp rises while driving in town. If it didn't drop while driving on the highway, that would be a concern for other problems.

In summary.... you are overheating due to the lack of air flow during slow driving ... fix the fan, and the cooling system may be low on coolant due to a leak... pressure test and fix the leak, if there is one.

Dmod81 · 04-24-06, 05:53 PM

I took apart the radiator support and gave the radiator a good cleaning, and that helped (there were a bunch of small rocks between the fins). I dug into the fan problem a little more and the short of it is that it is working. I just haven't had it hot enough to turn on in my driveway, and when I first checked it the A/C didn't get up to a high enough pressure.

I am not loosing coolant anymore, I have the level set about 3/4 inch over full cold and it hasn't lost any. Also when hot, it still doesn't quite reach the full hot line. Though, I still have a coolant smell in the passenger side engine bay.

I did buy the car in December from my father in law in Colorado. I noticed a couple good sized puddles of both oil and coolant after a drive in 15* (It was a warm day here in Minot...) weather and about a month of sitting. Haven't noticed much but wetness on the bottom and the passenger side of the engine since. It is also wet behind the distributor too, so I will be replacing the intake and valve cover gaskets. I will also replace the water pump, thermostat, and upper and lower radiator hoses since i think the pump may be weeping, and the lower hose looks pretty bad at the water pump. Some oil is leaking off the front crossmember under all the accessories, so I think I will replace the timing cover gasket while I'm in there.

So short version:
Not loosing coolant anymore
Still smell coolant in engine bay
Block is all wet
Will replace intake,valve,and Timing cover gaskets
Also will replace water pump, hoses and thermostat.

BTW--Car has 99,500 miles
Sorry so long.

Dmod81 · 04-24-06, 06:17 PM

Sorry, Didn't mean to waste your time. I will take your suggestion and get it pressure tested though as I obviosly have a leak somewhere if I can smell coolant.

As for the hot running, I just thought of something...

My father in law did flush and fill the coolant for me before he shipped it up here. He owns a corvette dealership/perfomance shop, and while I trust him, maybe it didn't get burped all the way. That would make it run hot and maybe even suck the coolant level down. That together with the cold weather leak could have been the majority of my problem.

WhalePirot · 04-24-06, 07:41 PM

Quote:

Originally Posted by Dmod81

I have a 91 L-98 and while driving through town (66 degrees outside), I noticed that the temp gauge would go very high.

There is quite a lot of info on this in past posts (Search, above), which includes cleaning debris from between the condenser and the rad. Your post does not make clear if you'd done that, but other comments show you have a grasp of the issue.

Nice to hear from someone who sounds quite capable beneath the Vette hood.

The stock C-4s run 220-230 but 260 is a bit hot!

Dmod81 · 04-24-06, 08:04 PM

Ya, I have cleaned the radiator. It didn't quite hit 260, probably more like 235 to 240. I wish I had the digital temp guage like the older and newer years.

WhalePirot · 04-25-06, 01:06 AM

I searched <radiator cleaning> and found two threads of interest. This one refers to the gathering of leaves and more in the wrong place:

Bottom feeder cleaning

Another, which you will easily find, speaks to coolant leaks.