I recently have added exhaust cut outs after the cat. My temeperature on average was running no more than 220 unless in traffic for sometime and it usually would heat up at while driving to about 180. Up till about a few days ago the car has been heating up to about 240 after about 15-20 minutes under cruising conditions and stop and go. Even while driving 65-70 mph the engine doesn't cool down. What could be the problem? The thermostat? I checked my coolant level and it's fine. If it's the thermostat, is it expensive, and is it easy to install a new one? I would really appreciate your help.

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• Red '91 Z-28 350
• 700-R4 Trans
• T-tops
• no major power
  gaining mods, K&N
  Filter, Flowmaster
  exhaust -series 80-,
  exhaust cut-outs
• Best E.T. 15.0@93mph, Will improve that 1/4 mile time this spring.
• HardlinePerformance

 

I wouldn't be driving it too much when the car is running that hot (240 is cooking the motor), first do you have a 160* thermostat, if not get one, I believe they are less than $20 plus you'll need a gasket. My car has recently been doing what yours has. There are a couple things to check. At upper RPMs does your lower radiator hose collapse, this can definately cause your car to run hot. Then there is the radiator is it in bad condition. I recently bought a 2 row aluminum griffin radiator for $180, I haven't had time to install it yet. Or you're water pump could be on the way out, which I doubt.

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'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER
EDELBROCK 600CFM CARB.
KN AIRFILTER
UNDERDRIVE PULLEY
ACCEL HEI DISTRIBUTOR
2:73 GEARS

 

 

160* thermo's are too cold for our cars. Buy a 180. That, with a gasket, probably wouldn't run you more than 5 dollars after tax.

Fans don't cool the engine while you're driving on the highway, only when you're going very slow. Check under your car to see if you have a black piece of plastic sticking out from the bottom of the radiator. It's the "lower radiator air deflector," if you have to replace it. It scoops up air while you're cruising to cool the radiator. (Usually it doesn't really help unless you're doing 45mph or above.)

If it's there, check to see if your radiator is blocked with crud, bent fins (there has to be a lot of bent fins for it to make a difference), dead birds, etc.

If that's not what it is, make sure the radiator fluid is actually going through the engine. Probably the easiest way I can think of would be to have the car fully warmed up and feel the upper radiator hose going into the engine. It should be pretty hot. Also, look at the lower radiator hose (bottom passenger side) and rev the engine up. If the hose collapses, get a new one.

And finally.. how to replace the thermostat.


On the intake manifold, near the front of the car, is the thermostat houseing. It's a black bubble-looking thing with a hose coming out of it running to the radiator. There's two bolts on either side of it. Take them off. If you can't get at the driver's side bolt, loosen the hose a little bit and slide it off some, that should help. Lift the housing off, and you'll see the gasket and the thermostat. If your radiator is nice and full, some fluid will spill out in this process, so if you really have to be tidy or whatever you can go ahead and drain the radiator some to prevent as much spilling as possible. Before you take out the old thermostat, remove all of the old gasket from the intake and from the thermostat housing. I say to do this before you take the thermostat out so you don't get any fragments of the old gasket into the engine. After it's all off, take the old thermostat out, put the new on in, put the bolts through the housing, put the gasket on the bolts, and then put the entire thing on the intake and then bolt it back on. (I do it like that because I find it's easier to line up the bolt holes in the gasket with the bolts that way.) And voila, you're done.

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else

 

Y'know what these guys didn't tell you? One VERY common cause for overheating is the air dam. Take a look under your nose and check out what it looks like!

 

I did too tell him to check for that! ehheh Were you to go to a dealer and ask for an airdam, they'd give you a part of the front fender. Ask for the lower radiator air deflector, and you'll get the black piece of plastic bolted onto the bottom of the radiator.

 

my car has a flex fan on it wich runs all the time and the car never goes over 185*..so fans do cool the engine when you are at cruising speed or in stop and go traffic.

 

I made my own air dam with an old metal bathroom fixture and some drywall anchors

Seriously.

 

One more thing that you should check is the cap. I had this prob. on my 92, i had the cap checked and it wouldnt hold a constant pressure. I may sound stupid but if the cap cant hold a constant pressure then the cooling system cant function properly. BTW the cap dosent have to leak to be bad

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1992 RS
Flowmaster exhaust
Hypertech power chip
180 thermo
Split fire plugs
Crane cams Ignition
K&N filter

 

I still have yet to see someone talk about how there car runs like poop after installing a 160 thermostat. Day and night difference when I installed mine. Best $10 I ever spent.

160 is NOT too cold for our cars. The car WILL warm up to operating temps!

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89 Formula 305 TBI
160* stat, 200* fan switch, K&N, Headers, 3in Flowmaster (hollow cat) back, pullies, 1.6 full roller rockers, B&M trans cooler, home-made ram-air
3.73 Richmond gears and SLP Zexel Torsen Posi (waiting for install)

 

What is the point of a 160 thermo and a 200 fan switch? When it's cool out it will run close to 160, when it's hot out it will run up to 200--until the fan kicks on. When it's warm out a 180 and 160 thermo will run the same temp--themp where the fan kicks on. A constantly varying temp is hard on parts, as well as mileage/efficiency. The tech section on this site has some suggestions...
https://www.thirdgen.org/newdesign/t...rheating.shtml

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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

 

What is the point? The point is that the car never gets much over 160 when cruising and never gets over 200 while ideling. I dont know about you, but the only variance in temp occurs when the car goes from driving to sitting at idle. Anyhoo, I doubt that a change from 160 to 200 and back would harm anything.

I read the tech article. It recommends changing the temp sensor in the head. My stock sensor was 220.

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89 Formula 305 TBI
160* stat, 200* fan switch, K&N, Headers, 3in Flowmaster (hollow cat) back, pullies, 1.6 full roller rockers, B&M trans cooler, home-made ram-air
3.73 Richmond gears and SLP Zexel Torsen Posi (waiting for install)

 

Yes I agree the same thing happend to me. For weeks of replacing everything I gave up and took it to my Repair Shop and it was the cap. Boy did I feel like a dumb***.



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'87 Trans Am:
(Engine)
305 TPI
160 Degree Thermostat
TB Bypass
Accel 300+ 8.8 Racing Wires
Accel Super Coil
Bosch Platinium Plugs
Custom Ram Air with K&N
Removed Emissions Equipment & Cat.
(Stereo)
Kenwood Excelon

 

 

If you run a 160 thermo, I would have a 170 fan switch to take full advantage of the cooler thermostat.


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82 camaro--original steering wheel, brake/gas pedals, seats--everything else modified
82camaro

 

fans do cool your engine on the highway. i burned a fan motor up while driving 70mph and overheated in about a minute.

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85 IROC 350 11:1keith blacks,.555lift erson roller cam,1.5 crane roller rockers,edelbrock intake,holley 4150 750dbl pumper, nitrous oxide,full length heddman headers,true dual exhaust, 11"stall converter, 700R4, 3.73 locker

 

82,

I originally had the 170 switch and never put it in. I thought the damn fan would run itself to death if I did. As long as the car is moving the temp drops. Its those long drive thru lines that get me.

I have two cars that DO NOT use the electric fan while driving and DO NOT have clutch fans. My 89 Formula and my 86 Ciera. The only time either fan will come on (brifely) is when the temp switches them on.

I've often wondered why some older cars have a clutch fan like my 79 Buick, have all that open grill, and still run hotter than my Formula with a little air scoop at the bottom. Are the water pumps different???

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89 Formula 305 TBI
160* stat, 200* fan switch, K&N, Headers, 3in Flowmaster (hollow cat) back, pullies, 1.6 full roller rockers, B&M trans cooler, home-made ram-air
3.73 Richmond gears and SLP Zexel Torsen Posi (waiting for install)

[This message has been edited by RGZWS6 (edited April 03, 2001).]

 

Unless you guys either have a mechanical fan, or something seriously wrong with the engine, the fan should not be cooling the engine while you're cruising down the highway. If it's electric, it shouldn't come on until about 220-230 anyways (stock), so if that's how hot your car is on the highway you need to check your cooling system some.

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89 iroc-z 305 tbi
k&n filtercharger, open element air filter. nuffin' else