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94 vette overheating

 
natrlone
I love my Chevy Chevette!
Posts: 10
Joined: 09/13
Posted: 09/05/13 06:27 AM

New here guys. Little history. Bought vette a month ago. It was running great though it seemed it was running too warm while driving, about 225-240ish estimated by looking at gage on dash, though no running isues or warning lights. This was before I researched what the fans come on at. Checked coolant. It had straight water and it was rusty. Did a good fresh water flush and got quite a bit of solids out. Filled with good coolant. Seemed to be holding steady. Car overheated one day and went into limp mode. Changed t-stat. Still almost overheated. Changed water pump. Still ran hot. Looked in void between condenser and radiator without removing shroud and saw a large patch of crud covering about 30% of radiator opposite cooling fan. cleaned with hose. Still ran hot.

Car sits at idle all day at around 195 degrees. Fans come on. Have bled system. It's only when I drive it goes into overheat. My air dam is kinda broken up so I'm thinking that my be my mine issue right now while driving.Do have a concern about the radiator though and possibly having some pluggage issues. When car is idling and running about 190 degrees and I squeeze the pump discharge to the radiator is just doesn't seem like there is much flow leading me to believe the pump is not getting alot of flow from the radiator. Is this valid? When you squeeze a water hose you can hear and feel the pinched flow easily. On my car it seems minimal.

One last thing. Seems unlikely but after I did the flush and fill it seemed to be running real good. I was looking at exhaust systems on line and had it narrowed to a magnaflow set of mufflers or a straight pipe muffler delete. Wanted to see how the delete would sound before buying anything so I cut mufflers off. Sounds like poo so I'm getting the magnaflows but the car overheated the next day while driving. Could not having the mufflers on in anyway be hurting this car and causing the overheat issues or contributing. It's obvious the car needed a flush and fill and air dam anyway but could this have pushed it over that edge?

Long read, thanks in advance.  

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waynep712222
My first time was in a Chevy
Posts: 129
Joined: 03/13
Posted: 09/06/13 06:05 AM

because i only have a few minutes... how many fans do you have??? one or two.. .do they both come on.

i seem to recall the 94 used two radiator fans...

and 2 radiator fan relays controlled only by the PCM..

90 96 C4 Radiatorcoolingfandiagram Zpse29f4c2b

if only one fan comes on.. it will over heat... usually the first fan comes on.. then the second

if you have a damaged air dam... yes.. that can change the air flow thru the radiator... causing an overheat..


look up the post i put up about scan tools for the C4 corvette.. it will be in the active posts.. perhaps only a few pages down...

with a professional version.. you can command both fans on.. for testing.. if your car has the C68 digital ac control you might be able to command it on for testing..

please... USE EXTREME care if you are thinking about back probing the relays to command them on.. you can blow the drivers in the PCM.. and ruin it...  

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waynep712222
My first time was in a Chevy
Posts: 129
Joined: 03/13
Posted: 09/06/13 06:05 AM

oh... and you will also want to swap in  duralast / wellsve or similar SU102  engine coolant temp sensor and pigtail...  both have broken and wear out..  this tells the computer how hot the engine is .. and then it can command the fans on..

its under 20 bucks.. and has caused owners headaches before..


235 is not out of sight for most C4 corvettes.. usually the fans don't come on till 228.. and your may not come on till 238.. but i don't have the spec infront of me..

scan tool... look for requests.  

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natrlone
I love my Chevy Chevette!
Posts: 10
Joined: 09/13
Posted: 09/06/13 06:28 AM

Thanks Wayne. Both times it overheated I noted both fans were running. I cleaned the radiator and condenser last night. Then started having other issues. See post on "Battery Issue?"

But when I did get the car started I observed that it ran until temp reached a hair over 185 degrees and first fan came on. Somebody before me must have changed factory setting. It ran in driveway at a hair over 185 for about twenty minutes so I believe the broken air dam is the main culprit while driving. I removed it and it was worse than I thought. After removing bolts the dam came off in several pieces.  

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waynep712222
My first time was in a Chevy
Posts: 129
Joined: 03/13
Posted: 09/07/13 06:12 AM

hmm... is the airdam one of these??

94 C4 Radiatorcoolingducts Zps65436e6f

or is it #32 in this image below.. as that seems to be still available from gm..  the aftermarket corvette suppliers probably have the pieces also...

94 C4 Lt1frontbumper Zpsb685a95d  

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waynep712222
My first time was in a Chevy
Posts: 129
Joined: 03/13
Posted: 09/07/13 06:17 AM

please also replace the radiator cap with one that does not have a loose disc in the center of the seal...

there is one that is like one part number away in the aftermarket brands... that has a spring loaded disc in the middle of the seal..

these loose ones are designed to be pushed closed by the expanding flow of coolant.. and they don't always work..

it made a lot of money for the repair shops and dealers when the cooling system did not hold pressure and the engine head gaskets blew because of the lack of pressure in the cooling system raising the boiling point of the coolant..  but thats just my opinion..

squeeze the upper hose... does the system hold pressure.. or does it blow coolant in and out of the overflow bottle...  or spend 7 bucks on a different cap and be sure..

each pound of pressure raises the boiling point of the coolant 3F..  so 15 pounds raises it 45F..

and does your engine have a proper temp thermostat installed???? so the coolant flows around many times inside the engine.. before it picks up enough heat to open the thermostat... then exchange hot for cooler coolant. then close the thermostat while the fans cool the stopped coolant in the radiator..


i have one more test... and its cheep...

got some sandwich wrap??? lay a piece over the radiator filler neck... push the middle down slightly to make a depression in it...  place a rubber band around it to seal it to the neck...   either crank the engine or start it and run it for less than 10 or 15 seconds..  the plastic wrap should NOT inflate.. if it does.. then you might have a blown head gasket or crack in the combustion chamber..

i have had the heads off several Lt1 motors.  not fun. but not impossible ..

please.. if you have to pull the heads.. invest a few bucks more and either spread some hylomar on both sides of the head gasket in a nice thin coat.. or use the spray on both sides of the head gasket..  i really don't like having to do things twice..

hylomar is unlike any other gasket dressing.. it is good for over 500F. and is resistant to most engine liquids.. and never gets fully hard.. seals  and stays..

the heads if the gaskets blown.. will need to be checked for straightness.. or just have them surfaced by a machine shop..  the overheating expands the aluminum in the hottest areas and since it cannot expand farther.. it distorts it.. leaving that area with a depression and not enough clamping force on the head gasket to create a good seal.  so the head gasket fails.. and replacement head gaskets fail unless the head is properly surfaced with the right equipment..  not a grinder by hand..  

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natrlone
I love my Chevy Chevette!
Posts: 10
Joined: 09/13
Posted: 09/16/13 05:54 PM

It's #32.  

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natrlone
I love my Chevy Chevette!
Posts: 10
Joined: 09/13
Posted: 09/16/13 05:55 PM

This may sound dumb but does car have overheat mode that affects brakes?  

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waynep712222
My first time was in a Chevy
Posts: 129
Joined: 03/13
Posted: 09/16/13 06:36 PM

these cars have anti lock brakes and most have traction control..

if you had battery cable issues...

you could have set a code and shut the antilock and traction control down...

when you start the engine... does the abs and the Traction control lights on the dash board come on for 2 to 5 seconds then go off ????



if the engine overheated... it could have set a code in the PCM or BCM.. or ABS/TC computer..

the master and power brake booster are up front in a normal location..

the traction control abs motor/control block and computer are behind the drivers seat in a cubby hole there..  

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waynep712222
My first time was in a Chevy
Posts: 129
Joined: 03/13
Posted: 09/16/13 06:43 PM

i guess i should just open a C4 speciality shop...

have the cars transported in from around the country.. like gm did with any LT5 motor issues.. shipped the whole car back to the mercury marine corvette engine service center.


it would be a shame.. as most of the issues i have found .. are actually bad grounds.. loose connections... and a few parts that have failed after 20+ years in service..

i never did get a straight answer back then.. that did the LT5 motors use antifreeze.. or salt water for coolant..  being they were an mercury marine built motor...

now the big question.. did MM use the LT5 motor in any outboard or inboard applications..  

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natrlone
I love my Chevy Chevette!
Posts: 10
Joined: 09/13
Posted: 09/16/13 07:28 PM

The reason I'm asking is because when the car overheated before to the point of 250 degrees and water boiling in overflow tank the car was slowing down on its own and downshifting even with foot on gas. This is how I saw it was hot as I got no other warning from dash lights. Just looked at gage when I was forced to stop. It seemed the brakes were dragging real bad. I thought it was some "limp mode" that applied the brakes to keep you from continuing driving and doing damage to engine. I was stuck at a gas station for about an hour. After the car cooled down I made sure it had enough water in it and it drove home okay. After replacing water pump and thermostat I took it out and it did the same thing after about 20 minutes of driving though the temp didn't show as hot. Then I cleaned that huge dirt patch I found on the radiator off, cleaned the ac condenser and radiator exterior with soap and water and flushed the cooling system. Then I took it out to test the temperature out and the car never got over 200 degrees but the brakes started dragging after about 10 minutes and I barely made it back to garage. Today I let it idle in drive until temp reached about 195 for a while and then took it out. Just two trips around the block and back to garage and the brakes were almost locked up. Car never got above 200 degrees. Turned it off. Jacked it up and could not turn either front tire by hand. Locked up tight. I now suspect I have a front brake issue that was causing the engine to work hard and overheat before due to dragging and the more I drove it the worse the brake problem got. The gage or digital read out never went above 200 degrees today but brakes lock up so tight car won't move. After sitting for 2 hours I jacked it up and could turn front wheels by hand but it seems hard. When this happens the brake pedal gets really stiff even just sitting still.

And yes those lights do come on and go back off when I start the car.  

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waynep712222
My first time was in a Chevy
Posts: 129
Joined: 03/13
Posted: 09/16/13 08:46 PM

thats a description of incorrect brake fluid in the brake fluid or a failure in the anti lock traction control valve assembly..


this is going to be complicated... but it starts out easily...

remove master cylinder caps.. do the rubber cap gaskets LEAP out at you.. as they have swollen to a larger size than the cap???

if so... incorrect fluid was poured into the brake master... probably power steering fluid.. or there was some cross contamination.. at a place that changed the oil in the car.. this not an isolated issue... they do hire low end help.. and fire them easily.. when they do.. fluids get mixed..

power steering fluid swells the seals and prevents the release of the pressure when you take your foot off the brake...


dirt in the system can also clog the TINY passages in the antilock.. traction control valve body.. and prevent the brake calipers from retracting..


so.. how many wheels lock up...

there is some complicated directions on how to properly bleed and flush CLEAN DOT 3 fluid thru the system

thats where i would start if the filler cap seals did not LEAP out at me..

##############

my girlfriends father decided to check all the fluids in his car.. he found a white bottle and topped off the brakes...  he made it about 8 miles... came home.. brakes dragging.. went in to call me..  while he was on the phone.. there was an explosion.. the caliper got so hot melted the wheel bearing seal and spread all the wheel bearing grease out... this actually caught fire.. and the fire burned upwards right thru the inside sidewall of the tire..  the tire explosion blew out the flames..  a new tire, rotors bearings .. 2 reman calipers.. 3 brake hoses.. a master, brake failure switch and 2 wheel cylinders.. and a 2 quarts of brake fluid to flush thru the system..

your car has a LOT more parts...

flush flush.. flush..


there are a few different sections...

http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c152800900a5


be sure to just pick out the info that covers your car...  

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