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CELT4RAGTOP

Well-known member
Joined
Mar 7, 2002
Messages
45
Location
Tampa, FL USA
Corvette
1996 LT4 Collectors Edition Convertible
I was out running some errands and stopped to visit my cousin, who coincidentally bought a 96 LT4 within a couple of weeks of when I bought mine. Anyway, on the way back I noticed that the temp was going up. 230, then 240. Tried to make it home but got up to 250 and I had to pull over. Overflow bucket began to boil, but never boiled over. Let the car sit for about 15 minutes and tried to get home. It was still at about 240 when I started and it spiked to 250 within a couple of minutes. Pulled over again, left the car for about an hour and came back and tried again. It went from 204 to 250 in less than a couple of miles, luckily that was all I needed to get back home.

Just had the radiator flushed and the anti-freeze (the red stuff) changed a month or so ago. I don't see any obstructions on the radiator (i.e. don't see any leaves or garbage bags up there)

What do you guys think? Thermostat? Waterpump? Both? Something else?
 
Joined
Jun 24, 2002
Messages
252
Location
Abingdon,MD
Corvette
1996 Torch Red LT4
Sounds like thermostat or waterpump. It should not keep climbing like that when you are moving. Mine only climbs while sitting still and then fans come on at 230 and it goes down. While driving I run about 194. Good Luck, Guy
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Betting Stat

But here's the question...

As the cars coming up to temp....

Are the fans kicking ON?

AND

Are the hoses firm when warm.. like the system is holding pressure?


Any water in the oil???


Vig!
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
I further assume

That the belt is in place and spinning all the correct pullies.....?


And the LOWER hose is not collapsed ( sucking in)


Vig!
 

CELT4RAGTOP

Well-known member
Joined
Mar 7, 2002
Messages
45
Location
Tampa, FL USA
Corvette
1996 LT4 Collectors Edition Convertible
Vig,

Went out to the garage and cranked her up. Hoses firmed up after around 200, but how firm should they get. I could still squezze the lower hose, but it definitely firmed up.

Belt was turning all the pullies that I could tell.

Lower hose was not collapsed.

Fan had not turned on at 235. I turned on the A/C and it kicked on immediately. However, the temp still climbed to 242 and I shut her down.

As for the water in the oil, I pulled the stick, but I'm not sure what water in the oil should look like. The oil did seem rather thin and dark, but I did not see anything like drops of water on the stick. I don't even want to think about water in the oil. I may not know much, but I know that's BAD, BAD, BAD! The oil was changed about 3,000 miles ago, if that, with Mobil synthetic.

Just sitting in the garage, the temp went from 180 to 242 in about seven minutes.
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Water in oil

Will look like a milkshake ( depending on amount of H20)

Next test

the radiator hoses.. are on opposite ends of the tank...

One should be cool..the other hot..if they are BOTH hot you have radiator blockage ( either air or core ).

There is also a bleedoff for air trapped in the system,, have to look for that.. if you have a big bubble your not flowing the amount of water you need to.

Fans not coming on @235...not good!

We need to force em on.. and see if it's an air flow thing or a stuck stat thing.

Why did you have the cooling system flushed?

What came out...YUCK.. or normal old coolant?

How many miles do you have on her?

Did this O heat thing start just AFTER you flushed?

I would get ready to do the stat..tomorrow!

Vig!
 
9

93 RRR

Guest
Shortly after buying my 93 Ruby Roadster she had the same symptoms. We found that the radiator flow was next to zero - the water pump wasn't the problem. The radiator however did have serious restricted flow problems. We sent the radiator to be rotted and rebuilt and all is now well. On my 92 coupe though, the water pump was a problem.
 

CELT4RAGTOP

Well-known member
Joined
Mar 7, 2002
Messages
45
Location
Tampa, FL USA
Corvette
1996 LT4 Collectors Edition Convertible
No shake

The oil doesn't look like a shake (thank god!)

Let the car heat up again tonight in the garage. The hose on the passenger side (which goes to the bottom of the radiator and looks like the one that goes to the thermostat) warmed up but did not get as hot as the hose on the driver side (could hardly hold it for very long.)

Bought the car at the end of Feb with 29.9K, she has about 33.5K now. I had the radiator flushed and the oil changed just for routine maintenance. Don't know what came out, cause I took it to the dealer (I know, I know, I should do the easy stuff myself, but with a 3yr old and a 1yr old its hard to take weekend time away from them.) I would assume that if it was gunked up, the dealer would have tried to sell me a host of stuff, but who knows.

Vig, from what you've said, it looks like the T-stat. I actually went to the local auto parts store to pick one up, but they did not have any and none of their local stores had one either. So, its either blow the Labor day get together and try to do it myself tomorrow or take it down the road and pay somebody and enjoy the day. She's my daily driver and I need her to get me to work on Tue.

Anyway, thanks for all the info.

Does the T-stat have any affect on the fan? The A/C was on when I started the car and the fan was on. When it got up to about 170 I turned off the A/C and the fan went off. The temp went up to 228 when I shut it down and the fan never went on by itself.
 
Joined
Jun 24, 2002
Messages
252
Location
Abingdon,MD
Corvette
1996 Torch Red LT4
Fan should come on @ 230 without a/c being on. This would be a problem but it still would not explain car getting so hot while it is moving. As long as I am moving mine never goes above 200. Good Luck, Guy
 

CELT4RAGTOP

Well-known member
Joined
Mar 7, 2002
Messages
45
Location
Tampa, FL USA
Corvette
1996 LT4 Collectors Edition Convertible
Thanks Guy,

Down here I always have the A/C on so I've never really noticed when it comes on by itself.
 
D

DHOUGHTON

Guest
Had same problem, did three changes, all better now

I installed a HYPERTECH Thermomaster chip. Easy 10 minute job. Installed a 160 thermostat and new gasket. Added Water Weter to the radiator. Before these changes my 90 coupe like to get really hot, tilt. Even though I wasn't running the AC. Now the fans come on much earlier. Big help here. The ne power chip not only helps keeping it cooler but made a big improvement in performance. Worth every bit of the cost.

marathoner
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
A simple test

Under the hood...... by the A/C plumbing there are 2 aluminum lines.

The Big one( A/C low pressure ) has a switch for the LOW freon cut off ( Black/Dk Green&white) if you pull this it will defeat the A/C clutch ( No AC )

On the smaller line there are 2 more switches on this line.. there is a BIG switch and a small one. pull the SMALL ONE.. this will tell the A/C computer that the HIGH side is up to pressure and will turn on the fans.
( fooling the computer)

Pull the 2 switches start the car and in 10 or so seconds the fans will come on FULL BLAST

See if the car will hold temp at this point.... if it doesn't.. you have either stuff in the radiator..really inspect it CLOSE or you have a funky Stat.

Also open the air bleed line ( fitting ) located on the snout of the stat housing.. PUT RAGS UNDER THE BLEEDER you do not want coolant leaking on the OPTICRAP..or you will have another thing to deal with!

FYI 260 degrees is when the HOT light comes on.....YIKES!


Vig!
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
And if you want to BLOW the radiator out

Use compressed air...not the garden hose... water on the front end of the engine is deadly!

Vig!
 

vettn94

Well-known member
Joined
Aug 9, 2002
Messages
181
Location
Warrenville, IL.USA
Corvette
1994 Polo Green Convertible
with the fans not coming on is it possibly a bad relay ? or since you're constantly running the AC maybe the fan motor has burnt out ?

Just a suggestion but if you're going to change the Tstat I would recommend getting 160° and pick up a Hypertech Power Programmer so you can re-program the fans to come on earlier after you figure out what the problem is.
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Any progress?

Still need help?

Vig!
 

tyrel

Well-known member
Joined
Sep 7, 2002
Messages
574
Location
Portland
Your radiator fins may be clogged. You cannot see if the radiator is clogged without pulling it, as the thing you see when you look underneath the front of your car is the a/c condenser.

I pulled my radiator last year and there was so much garbage between the fins, leaves, dirt, etc. I blasted the fins with a garden hose and blew out lots of crap. After I reinstalled, my coolant was 30 degrees cooler and it never goes over 220 even in stop-and-go traffic with the a/c on.

So I recommend cleaning the radiator as part of any regular maintenance of a C4, depending on how much you drive the car.
 

CELT4RAGTOP

Well-known member
Joined
Mar 7, 2002
Messages
45
Location
Tampa, FL USA
Corvette
1996 LT4 Collectors Edition Convertible
update

Thanks for all the help and suggestions. It's been crazy busy at work since Labor day (14hr days trying to get tax returns done).

Anyway, I was going to try to change the thermostat on Labor day, but ran out of time. Sooo, on Tue morning I dropped the car off at Goodyear (about a 1/2 mile from the apartment) with KY in hand, fully expecting to get hosed (if you know what I mean). Well, they changed the thermostat and called me at work to tell me that it was still overheating. I thought "here we go". They next replaced the coolant temp sensor. After that they said it was still getting up to 230, if parked, but the fans would turn on and the temp would go down. Picked her up total cost was about $213. Not great, but could have been a lot worse I guess.

Anyway, she's been running OK since. She goes up to 220/225 when stopped in traffic, but goes right back down to 200 once I get moving.

I still need to go back and read everyone's suggestions again and the other "cooling" threads. I'm sure she could run cooler. I did notice some leaves up on the very top part of the radiator once I checked again, so I'll take your advice Vig and tyrel and try to find somewhere close with compressed air to try and blow out the radiator.

That's all for now.

Thanks again everyone for all the helpful hints and suggestions.

The CAC is truly full of first class people.

Louis
 

WhalePirot

Well-known member
Joined
May 9, 2002
Messages
2,942
Location
SoCA
Corvette
1984 White Z-51/ZF6-40/Shinoda body
FYI

My '84, w/ hi-perf 406, idles happily at 205 deg. with stock water pump; stock '84 radiator, in 90deg weather, as long as my fan is left ON.

:w
 

vigman

Motor head!!!!
Joined
Feb 13, 2001
Messages
3,471
Location
Valencia, CA,USA
Corvette
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
With KY in hand

To funny...( but I know the feeling )

Well good news!!!!!!

Now clean the front of the radiator.. and you will be in good shape.....


But if I recall the car would O heat as you were driving as well correct????

So the stat might have fixed one part of the problem!



Vig!
 

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