Ok guys i just picked up my new ride...92 z28 5.0/auto. 28k miles. Had some problems on the long ride back related to sitting for awhile (rotted radiator caused huge coolant leak, bad fuel pump/fuel filter caused surging. AFter about $1500 at the chevy dealer in the town it broke down, it was roadworthy. They replaced everything--new fuel pump, fuel filter, new radiator, all new hoses and clamps, new air filters, new belt, etc. etc. etc.

The ride home was 530 miles and the car road seemlessly. At one particular tollbooth, the car seemed to heat up very fast as we waited in line. Much faster than i remember my previous 92 RS (305 TBI) heating up. It went from the cruising temp of 160F to about 220F within 1-2 minutes of slowing down/stopping. After a few more minutes it almost got up to 240F. That seems waaayyyyyyyyy high and wayyyy to fast. Also, right when we got off the highway just now to come home, we noticed it heated up to almost 220F. I mean there were just a few stopsigns and about 2 miles between the highway and our house, and the driving was pretty slow (30-40mph max), but the car shouldnt get that hot.

Please help me diagnose this problem, as it poses a problem to me because i dont really wanna drive it anywhere when i know it heats up soo fast at even the slightest stop or slowdown.

From what i understand the factory fan switch comes on at 225F? so tha tcould possibly be faulty if the car was reaching almost 240F...but neverless that still doesnt tell me why the car got to that 220F mark much faster than it seems it should (or atleast it did on my 92 RS, which had 45k miles).

 

The fans should turn on around 220*. So the switch may be bad. Did you hear the fans coming on? If not, let the car heat up and get under the hood to check. And I would assume that the dealership that performed the repairs would fill the radiator and whatnot. But did they flush all the funk out of the block? You may want to check that as well. Good luck and get some pictures of that thing already!

 

It might be a combination of the fan switch and a fluid leak. Park it on cement and let it run. That way you can look for the leak if you have one.

 

The dealer put all new coolant and everything in. We didnt notice any coolant leaks (there shouldnt be since all the hoses were replaced and what not).

I'm sure somethng is either wrong w/ the fans or the fan switch because it got to almost 240...but why on gods green earth did this thing go from 160* to 220* in like a minute...that seems alittle fast.

 

check to make sure your air deflector is still intact and directing air into the radiator. also check the fan connecter underneath the stock air box/ charcoal canister area. my was not plugged in properly when i bought my car and would heat up like crazy when the car was sitting still. hope this helps.

 

Did u get a new water pump too?

 

That could be it too. Check and see if the water pump is dripping fluid from the weep hole in the bottom of the pump. That's when you know it's about ready to quit.

 

No,its the original water pump.

could that make it heat up sooo fast??

 

If the pump isn't circulating the coolant then the engine will get pretty hot. It's just one possibility though. If the pump needs to be replaced it will start dripping fluid from a little hole in the bottom. It may drip down onto the crank pulley though so look very closely.

 

My white one needed a water pump...It dripped a drop or two every time you shut it off and the engine wasnt warmed up...but i never had cooling problems w/ the other one. This one has no water pump leak.

I mean for all i know these cars w/ a stock t-stat and fan swtich could heat up that quickly. I dont know, i wish someone w/ a TPI could tell me for sure how fast it usually takes for their car to heat up. I just found out that the TBI fan swtich turns out 15* cooler than the TPI one so thats one of the reasons my TBI didnt get as hot as my new car. I just want to know if what i'm experiencing is normal or not.

After all the **** i just went through to get this damn thing home, i'm insanely paranoid over everything.

 

You can check that your fans work by jumping the ALDL at terminals A and B,like checking for a code ,this should turn on both fans without getting the car hot.

 

My first thought is fan relays. If the fans aren't operating, the engine will run cool at speed, but it will get very hot when moving slowly or not moving at all. In that case, you'd want to keep moving, obviously, as effortlessly as possible(no power options, no a/c, downhill if you have a choice, etc.). Don't laugh at the downhill part, lol. That really saved me once! It got me out of traffic flow and allowed me to get the engine cool enough to park it until nightfall. Then without the heat of day and no rush hour to deal with, and I was able to make it home. Anyway...

The primary fan 'switch' is actually the coolant temp sensor in the front of the intake manifold, and its readings allow the computer to control that fan. The secondary fan is controlled by a sensor-like switch in the cylinder head between plugs 7 & 8. And if a dealer did all the work you mentioned, then I'd guess he installed a new 195* stat, too.

If the primary fan doen't come on at all(around 220*), then your next on temp is around 240* with the secondary fan. But at that point, I doubt the secondary fan alone would be up to the task of keeping you from overheating if you had to sit in traffic. But because you were on the freeway and able to get moving quickly again, temps stayed somewhat under control, fans working or not. So I'd definitely check those fan relays(located next to the end of the radiator on the passenger side, if on the same side as the Firebird) to be sure they're connected and working. Also check to be sure the sensors are connected. And don't just accept it if they LOOK like they're connected. I'd disconnect them and reconnect them, making sure they're secure.

 

The primary fan (which im guessing is the on the drivers side) works...and seems to turn on right around where the gauge reads 225-230ish...even with the car sitting in our driveway running at that temp, it wouldnt get hot enough to turn on the secondary fan. It still seems to run hotter than my TBI car...is that normal (i know that the TBI cars fan switch turns on at 215*). And what other type of CTS's/fan switches do they make. Obviously i want to go with a cooler one, along with a new thermostat. I already have a 180* t-stasrt...but what fan switch do i get???

 

lok into aftermarket. Hypertech ha an adjustable fan swotch that is reccomended around here quite a bit. I took the easy way out nd just wired a switch into the relay ground so I can turn off the switch and it runs factory hot as all get out, or I turn ON the swotch and the fan runs constantly. just a thought.

 

You're right, the primary fan is on the driver's side. The CTS sends temp information to the PROM, but it doesn't control the fan. The PROM controls the fan. So the only way to change that temp is to reprogram the PROM. If you're not into custom tuning, someone here or close to you could probably help you out. But if that's all you want to change, and you plan to keep everything else basically stock for now(or always), then contact site sponsor TPIParts.net. Angel, the owner, programs adapters for stock chips, making simple changes like that for a reasonable price.

With the stock 195* stat and a primary fan on temp of around 220*ish, yes, your TPI engine might seem warmer than your TBI engine, although I'd think they'd be set-up similarly, temp-wise. But if temps aren't getting high enough for the secondary fan to come on, providing it works, then I doubt you have a problem. The primary fan should be able to control temps without assistance, and it sounds like it is.

But that secondary fan switch can be changed to a lower temp one. It's not computer-related. I've never heard of an adjustable fan switch, but both Jet and Hypertech have 180* switches(Jet's is on at 195*/off at 185*, and Hypertech's is on at 200*/off at 185*), but you can also buy similar switches of various degrees from auto parts stores, probably for less money. But you can see that if you don't reprogram the primary fan temp in the PROM first, your secondary fan will be coming on first... which I suppose would be ok.

The 180* stat is good. That'll help keep the car cooler at speed. Then at idle or in traffic when the engine is warmer and a fan coming on around 190*-200*, your system should work well at keeping things cooler. But if you just want to install the stat for now, no reprogramming of the computer is necessary, and that will help whether you do or don't change fan temps.

Sorry for the long post and all the detail. My posts tend to get that way, lol.

Now... what the heck are you doing in the house sitting at the computer on a beautiful afternoon like this while that gorgeous car waiting for you outside?! Nothing could keep me from being out driving that car right now, and I'm sure there's a nice, wooded highway out there calling to you!

 

Summit Part - summitracing.com

 

Sounds good... What would you recommend as far as fan switch temperatures? I'm not really into performance and the car is NOT winter driven so i dont need something too radical, just something to complement the 180 tstat nicely.

Also, does GM make any lower temp fan switches? If possible, i prefer to use all GM parts.

 

You're still in the house!

GM does have a small assortment of temp switches, but you'd have to know the part number for the one you wanted, because that's all the info the parts guys will have. They won't know temps. I'm pretty sure I've seen the different part numbers/temps posted on TGO in the past, so doing a search might locate that info. But any brand of switch should be just as good... maybe even made by the same manufacturer.

To compliment your 180* stat, I'd go with a switch in the ballpark of Hypertech's 180* switch(on at 200*/off at 185*). I like the 20* spread between stat and fan temp. But again, if you don't change the primary temp in the PROM, then your secondary fan will turn on first, making it, in a sense, the 'primary' fan and making the computer-controlled fan the 'secondary' fan.

I don't know if that would affect the computer or not. I've read some people say that the computer will detect the secondary fan running, and it will automatically turn on the primary fan, too. That's never happened when I've run only my secondary fan, so I'd say that's not true(unless that's an a/c-related situation). But if it is true, then you'd be in even better shape because both fans would turn on at the lower temp.

 

Do you have any idea how much a GM/delco fan switch would cost? I just checked summit and the hypertech fan switch costs about $42, which seems alittle high considering a new thermostat is like $3.

 

fan switches are $30-50 at part stores

 

I don't know what a switch from GM would cost, but it's likely to be one of the more expensive switches available. You'd have to ask your local dealer. But he's likely to only find part numbers based on vehicle-specific applications, not temp info.

There are some topics with temp info, and one stock GM application I found was for the Buick Grand National, which was '86/'87, I believe. So asking for that would get you a switch in the 200* range.

Here's a topic that lists a few aftermarket switches, besides Hypertech and Jet, and they're available from local stores. This topic is a couple years old now, so prices and availability might have changed:

https://www.thirdgen.org/forums/cool...n+switch+temps

I usually prefer using 'GM' parts, too, but for something like this, I really don't think quality would be an issue, so I wouldn't worry.

 

ok im just about to order my fan switch...does it even matter if i go with a jet or hypertech or are they both exact same quality. (I know the jet one is 195/185 where the hypertech is 200/185 but im talking more about quality)

 

I don't know which, if either, is considered better quality. I know a lot of people use each, if that means anything. I really don't think there's much, if any, difference in quality with this kind of product, so I'd use either, as well as any from an auto parts store, if I liked the temp range.

I just purchased the Hypertech(200*/185*) to use in the new heads I'll be installing soon--not because I think it's any better, but because I didn't want my secondary fan to turn on before 200*. The Hypertech was closest to what I wanted.

 

I just ordered the hypertech 200 on/185 off fan switch. it should be here tommorow or friday. how long should i expect to install this piece? and are there any tips when installing one?

 

My 86 with the one ecm controlled fan would run at 195 all day long as long as the car was moving without the fan ever kicking on, however, sitting in stop and go traffic would make the temp go up to the fan-on setting pretty quickly.

 

Someone in another thread asked recently if he needed to drain the coolant to install the switch, and someone else told him, 'no, just install it quickly... and don't be underneath the car when you do it.' Sorry, but that just struck me as funny! I suppose you could do it that way, and many people, maybe even most, prolly have, but I'm not gonna suggest that.

A good time to install the switch would be when you install a new stat because, yes, it would prolly be better to drain the coolant, or at least, some of it. And the switch will be easier to see and reach from underneath the car. And it shouldn't take but a few minutes, depending on how long it takes to remove the old one.

 

when my dad and i were changing the oil in the car today, we took a look to see where the fan switch is located. My dad said its in a pretty small area, and has a very close proximity to the oil dipstick tube. I'm wondering if we're going to need a special tool or something like that. Just wondering how you guys went about installing it.

 

Ive just done mine, 88 5.7 iroc,
Breakit free from underneath with a wrench.Then turn it out from on top.
I

 

Most likely you will loose some coolant,unless you drain the block.
So, in other words,do it quick, unless you want to lay under it.
Hope it helps you.

 

I have the same problem with my '86 Z28. Turns out I have a blown head gasket. Maybe a cracked block but don't know yet. I'm trying to decide if it's worth $600-800 and up to even start with the gasket. Car is worth $2K. Any advise?

 

make sure that you arent low on coolant/water as well.

pop the rad cap and poor some water in till it reaches the top

 

Cool, that worked. Thanks bro!












Just kidding, My buddies talked me into replacing the head gasket myself (had 2 $1700 quotes today). I'm going to see what I can do. Worst come to worse if I screw it up to bad, I'll donate it to the kidney foundation I hope I can fix it 'cause I love this damn car. The stereo in it is killer, it makes me feel like a teenager again. Its an '86 and I graduated in '85. The body looks like **** but the interior is almost perfect.

anyway, I'm sure you'll see a few threads from me about how to replace it over the next month, lol.

 

damnit!


it may seem trivial, but ive seen it happen numerous times.

 

1700 bucks to replace the head gaskets?

****, that seems really freakin high.

I could see 4-500 ??

 

I was gonna say that too, if the new fan switch dosnt solve the problem consider doing a compression test. Another thing to try to check is determining if there is air in the cooling system, this will cause the car to heat up really fast. Took me a while to get the cooling system on my 89 IROC-Z working tops, eventually I got it to the point where it would not go higher than 200 in any situation (stop and go traffic and/or track road course racing and drifting). I was using a 180 degree thermostat w/ a 1/8th inch hole drilled in the fin, a 180 degree fan switch, two new fan motors for the stock L98 dual fans, and a bigger than stock radiator (that was only necessary because of the track racing). But then one day out of the blue it began shooting up to 230-240 again during a track session. After attempting to troubleshoot I determined that the cooling system was still good, but my headgasket had failed. This is why the compression test is a good test to do if the cooling system is suddenly failing for an unknown reason. Checking the coolant/fluid is also a good idea when you have cooling problems. If there is unknown stuff in the fluid (discoloration or buildup/crap) then you know there is a leak somewhere in the system be it external or internal. And when there is a leak thats a prime oppurtunity for air to enter the cooling system, this is what causes problems. Along with the components of the cooling system you should also keep in mind what fluids you're using in the cooling system, because that can also play a big role in how fast/slow the fluid heats up. Watch out for products that promote themselves as being better because they have the highest boiling temperature, its a marketing hype. What you want is a fluid that has good heat exchange rates as well as high boiling temps, this is usually a mix of coolant, distilled water, and other additives (Redline or Royal Purple, etc).