UH-OH!! Did I make a Mistake ? Overheating now!!

[Idaho Slim]

Just got my 96 LT-1, auto trans, back from the dealer,(56K miles) had the following done;
- Replaced intake Manifold gaskets & seals for oil leak, & replaced vacuum valve
- Oil change
- New fuel filter
- Cooling system service; Drain, Power Flush & Refill
- Spark Plugs changed, (AC Delco #25166821) (Wires were good), Timing not checked(said it doesnt need it ??)
- And................. Since they were there I had them install a MR. Gasket 160 degree thermostat.


On the way home driving temps were dramatically changed, 171 degrees , @ 70 mph, in 70 degree weather, at same conditions b4 thermostat change engine temp was 205 degrees. Thought all was good, till I got home and while car was sitting idle in the driveway for 2-3 minutes while i got mail, temps rose to 225+ and would not decrease when i moved into drive way , and lightly rev'd engine............... Temps never increased like this at idle before this work.

So my question is , Is there something I am missing with the 160 degree thermostat change that causes these temp increases since I have not done the TB Bypass mod yet?? I am planning to doo it in the next 3-4 weeks, but ambient temps here locally will soon reach close to 90, and I know when the wife drives it daily to work, when she sits in traffic for any time at those temps.. we will have Twouble!!!:cry

OH................ and it may just be my paranoia, but for some reason I thought the performance was less than when I took it in, and since i replaced the plugs, and it was running cooler, I expected an increase ??????????

Any thoughts??

 

[Edmond]

Slim,


I read somewhere that beyond a certain age of the car, a complete flush of the coolant is not advisable. I think the reason they gave was because it would dislodge too much stuff and the vehicle would overheat. I could be wrong though.

Have you tried some Water Wetter? They're about $7.00 a bottle and I used two bottles in my 88' last summer and the temp never went above 190, even in the 100 degree weather.

 

[Idaho Slim]

Thanks for the reply Edmond, boy Ihope it hasnt caused debris dislodgment. Only 56K miles, I'm hoping it fairly clean inside, but you never know. :confused I intended to get water wetter during the next couple weeks also, but what disconcerts me is the difference in the cooling characteristics that i did not experience before this work, (Assuming all the work is correct), guess I'll keep an eye on it, and give the dealer a call this morning. Maybe they have an idea.

So is it safe to say, that adding just the 160 degree thermostat without the TB bypass, does not cause this idle over-heating ??

edit ...just got off phone with dealer, when radiator flushed, it looked real clean, in fact may not have needed it, also, vette mech thinks its definetly 160 thermostat related, will keep an eye on it and get my ars in gear to try and doo the TB bypass, which they said should cure the problem.

ok.......... i have threads that help me doo the TB bypass, but what about parts for it?? I had read that ordering the Mid-America kit isnt necessary, so what should I use in its place?? Thanks everyone.

 

[vette-dude]

Did you burp the system? After refilling you have to open a couple of bleeder valves to get the air out of the cooling system.


Randy

 

[DRTH VTR]

I have seen posts by c4c5 specialist saying that the cooler thermost is not a good idea. The engine is designed to run hotter than that and piston/cylinder clearances are affected by cooler temperatures. I am not sure whether this applies to the LT1 or LT4. He was speaking of the LS1 and LS6, I believe.

 

[c4cruiser]

One possibility is that the radiator core is clogged with debris. C4's are "bottom breathers" and it's easy for stuff on the road to be sucked up into the radiator. If you look up under the license plate you will see the opening and the front of the A/C condensor. There is a small gap under the condensor for air to flow into the front of the radiator.

Open the hood and with a flashlight, look thru the gap in the radiator shroud where the A/C lines go to the condensor. If you see a lot of junk in there, that may be why you see temps rise quickly when there is no air flowing thru the radiator core. Yo ucan use either a low pressure spray of water or air to dislodge any junk stuck between the cooling tubes. Air pressure may work a bit better as you can stick a 1 1/4" vacuum cleaner hose thru that opening and suck out the debris.

Turning on the A/C will force the secondary fan to start, so if you see high temps while stopped, simply turn the A/C on and the temps will go down. You might watch the secondary fan to see if it does come on. At operating temp, turn on the A/C; the secondary fan should start. The secondary fan should start somewhere around 228 degrees and shut off at 185-190 or so. If the fan isn't working, it may be due to a bad fan relay.

I'm not a fan of cooling system additives like Water Wetter, They are only a temporary fix and if your system is clean with fresh coolant you should not have any issues. I had read somewhere that Water Wetter will lose its effectivness after a few months.

The dealer tech should have known how to bleed (burp) the air from the cooling system. Getting air pockets in the passages can very well cause increases in temps bu if they used a machine to flush and refill the cooling system that may not be an issue.

A TB bypass will not really help a lot with lowering temps. The coolant passes through the TB to help with emissions by getting warm air into the intake manifold. Cold air will provide more power, but emissions will rise a bit. A 160 thermostat only really helps by opening the coolant flow at that temp. Once it's fully open, it is not really different than a 195 'stat when it is fully open.
Engine spark timing is set by the ECM so there is no way to really adjust the timing unless you use a Hypertech programmer.

I have a 180 'stat in my 87 and in cool weather, temps stay right around there. As the weather heats up, coolant temps will rise to 185-190 above 40MPH. My 92 has the factory 195 'stat and I usually see temps between 194-210 while driving regardless of the outside air temp. Temps will climb to 230 if I'm stopped in traffic, but I can tell when the secondary fan kicks in as the temps will plummet at that point.

 

[warren s]

Sounds like there is air or dirt in the system.

Changing to a lower temp therm will not hurt anything. The high operating temps are for emmissions only. But you will only get the benifit of a lower temp therm when there is air moving accross the radiator.

Consider putting in a fan overide switch, see my website.

 

[86er]

The 160 T-stat should not be an issue, it just opens a little earlier, unless it's faulty and stuck closed. The 160 would only cause problems in the colder months where the engine would not be able to warm up enough, but some people change in the winter and back in the summer if its an issue. And even though you've got a 160, you're car will almost always run wamer than that.

Sounds stupid, but make sure fan(s) are turning on for starters, you'd be surprised!! If work was just done, it's easy to forget to plug something back in.

If it wasn't overheating before dealer service, more than likely its probably electrical plug, relay, hose, etc........ I doubt the T-Stat.

The TB Bypass probably won't help as for as your cooling problem, but is a nice little mod to do since you're under the hood anyway!

 

[Vettefan87]

I think you are fine changing to a lower temp T-stat, I never liked mine getting that hot so, I put a 160 in my 87 then I put a thermo master chip in that turned the fans on at 175. If the fans check out ok and they work. Then you might have a air pocket in the system. You can be suprised at how big they can actually be. Is there any low coolant light on?

 

[Idaho Slim]

Thanks Everyone For All The Suggestions!!

I am still trying to run this down, (delayed since I'm busy at work ) I will be checking things out this weekend, the wife sez no over-heating probs while normal hwy driving speeds etc. runs nicely at 172 degrees. 45 - 70 mph and above

1). Going to check the fans to see if missed getting hooked back up.
2). Also, if any debris under radiator.
3). And, thanks for the suggestion of air pockets and coolant levels, I was going to pop off the cap and see that also.

I will report my findigns. Thanks again folks.

edit, no low coolant warning vettefan87, thats good to know!

 

[rrhayden]

I had a similar issue last summer after changing the thermo and water pump. I located some info ( cant remember where) about air intrapment near the thermostat. It suggested that you drill two 3/32 holes in the thermostat before you install it. This will stop an air pocket from forming below the thermostat. If thst happens, the thermostat will not open at low rpm

 

[jmccloud]

cold t'stat

The reduced temp t'stat will lower the control point of the lower temp end of the range. The upper end is controlled by the fan cut-in temp which is typically about 230 F. Sounds like you're operating in the normal range. If you want to lower the max temp. the fans will have to be reprogrammed to cut in at a lower temp.

 

[kenwa]

My thermostat and water pump started leaking last year and I had them replaced, along with a flushing the system. Before, I cruised at 185 degrees, and after the cruising temp was 195. I may have had a lower temp thermostat in there before; they put a stock one back in. Afterwards, the car seemed to heat up to 225 at stoplights sooner than before. I had the shop check it all out (pyrometer, fan programs, etc) and all was fine. I figure the clean system was just better at absorbing heat than before. BTW, LT1's have a two-stage fan setup. The driver's side fan comes on at 210 and the passenger side comes on at 225. So, 225 is all you'll ever see. It won't hurt anything.

Ken

 

[vetteboy86]

I am curious how do you burp the system. When i put the new thermostat in the car, and flushed the radiator i just let the car run a while with the radiator cap off. I was told that if there are any pockets of air in the system that they will come out. I assumed that with the cap off any trapped air could escape. Was i told wrong. Where are these bleeders that Vette-dude was talking about.

thanks

 

[WhalePirot]

Stat temp is only part of the story; flow is the rest.

A Robert Shaw (a few bucks at AutoZone) flows enough MORE water than the Stant to make a very noticeable difference in my 406. Finally, the hi-perf pump and radiator worked as designed, whereas the Stant made me wonder why I spent the bucks on those parts.

I bled with the cap-off, bubble method.

Check that the fans come on, while it is idling; watch the indicated temps. Seems you have good enough cooling while moving, so the fan ops are suspect.

 

[Idaho Slim]

Hmmmmm....................

Well, I took all of this new found info and ideas saturday and fiddled with the vette. The things I found were.................

#1 ....... Coolant level was down about 3/4 of a gallon, filled to spec level.
#2 ....... Thanks to c4 Cruiser. There was A bunch of gunk stuffed up in the top of the rad/ac cores. Vacuum and air hosed out all of it,WOW ! what a load!.I think i will fabricate some kind of free-flowing screen at the bottom so as to allow easier cleaning. It does catch a lot of road debris, feathers, weeds etc.
#3........ Insured the fans come on as required. All working fine.
#4 ....... burped the system, dont know if this was the prefered method, I crakced the radiaotr cap while it was warm, and actually got it to release air 4 times.


So what did all this doo???? .......

Nothing .............:confused However, the local temps have incresed to mid 80's, i am wondering if this is just a coincidence of a combination of weather warming up for the summer, the idea that kenwa described of the new cleaned system working correctly and the 160 T-stat mod that rrhayden suggested. The motor temps are as follows now, warms up to 171 -180, and if I then go drive it, will work up to an operating temp of 185 - 208 dependant upon how much i use my right foot , but if I let the car idle after warming up it will move to 228-230, at which the fans doo kick in and it will drop to 210 ish while sitting in the drive, and will not go lower until i put it in gear and start a drive....... so from what i am gathering all is well and the vette is operating normal, however, the car is going back to the dealer tonight to fine-tune some of the work they did, adjust brakes etc. and I will have them recheck everything in the cooling system, any thoughts??

btw, what kind of slow idle temps does everyone see in the heat of summer, like here where june-august it hovers around 95 to 110 during most of the day ??

thanks all.........

 

[warren s]

Your numbers seem normal. I also have a 160 therm and get similar temps., though it take more than a few minutes to hit 230 standing still in summer heat.

I switch on the fans around 210 if i think I will be in traffic for more than a few minutes.

For a $3 switch and some wire its the best investment you can make. It does not affect the normal fan operation.

 

[JRMaroon]

btw, what kind of slow idle temps does everyone see in the heat of summer, like here where june-august it hovers around 95 to 110 during most of the day ??

It gets plenty warm during the summer in Atlanta and my temp never gets above 230 in traffic at idle. The fan program may be different on my '94 but they turn on at 228 and shut off at 217. From what I've read, this is to specifications for my year.

I don't like to see it get that high so I turn on the Air Conditioning which starts the fans when I'm stopped. This keeps my guage in the 190 - 205 range depending on outside conditions.

Jeff

 

[WhalePirot]

methinks U have normal #s

and will not likely see higher numbers during the summer.

The still temps show your fan operating, which in not needed with speeds above 50+/- mph. Later ECMs cut out the fan ON above 55mph.

The A/C switch is great (and the cheapest) manual fan switch.

Congrats on getting your cooling system up to snuff. Many other threads offer advice on changing your fan trigger temps. It varies by model year wheter the ECM or a separate sensor needs changing.

The thermostat, regardless of rated temperature, controls how much coolant flows and at what temperature it SWITCHES open and closed.

 

[Jersey-vinny]

IDAHO: Also consider changing the temp sending unit to turn on the fans at a lower temp. Look in the Eckler's or Mid America catalogs for this part. Mine turns the fans on at 200 degrees and am very happy with it.
VINNY