2002 still getting hot after changing everything
 

My problem started a year ago getting hot on the freeway. It never got to 260, but was way to close. Let it cool and nursed it home with many breaks. It had always run 195 since it was new. Changed the thermostat and all seemed good. Until lately, i can't go 2 miles without it getting hot. So new thermostat again, still hot, new radiator, still hot, REBUILT head, new gasket, new bolts, still hot, new water pump, still hot, hoses are not hard, out of shape, or sucked shut. No bubbles in the surge tank so head job is OK. I never see the fan come on unless the ac is on, which in AZ. is all the time anyway. 60 or so on the freeway it gets hot, drop into 3rd and hold 3200 rpm and the temp goes to 195 or just under. At a stop light temp goes up till i hold 3200 rpm in neutral, drops to 195 again. Help. What have i missed? its a 2002 cavalier 2.2 ohv 4 cyl. I'm going to get the attention of every law enforcement officer in the area if this keeps up. I dont like the look in my wifes eyes as she's looking at new cars we really cant afford...

New thermostat does not mean good thermostat. I'd try changing it one more time, maybe different one.

How much did you spend on your new surge cap?

What brand is it? I'm merely assuming you have the new

type system with no cap on the radiator?

If it's a two fan, one comes on with A/C, the other is a temp sensor controlled, that'd be where I'd look.

The cap on the surge tank is 10 months old, replaced with first thermostat from Napa (now on #3). Haven't even been able to go anywhere since the new radiator. Still gets hot. The system only has 1 fan. The hot coolant splits somewhere and most goes through the radiator and back through the thermostat to the pump. The 1" split off hose goes straight to the back sensor area of the thermostat and on to the pump. The thermostat, 1" hose and pump make a "Y" like configuration. The top radiator hose is to hot to hold, same with the 1" hose, the lower radiator hose at the front of the thermostat feels like warm bath water. When the car cools down at 3,200 rpm it drops to the 195 degree of the thermostat. Rigging the fan to run full time didn't cool the engine. I'm ready to restrict the flow from the 1' hose so it pulls more from the radiator. Going to Napa for #4 stat tomorrow.

see post #4

Did some testing in my garage at 80*.
#1 back flushed the Radiator and Engine. #2 Rigged a manual switch for the one and only fan. #3 gutted the old t stat and installed. Ran the engine for 30 minutes without the fan to reach 195*. Turned on the fan and the AC for giggles. 20 minutes later it was 122* and still dropping. Great, everything works as it should.
Retest
Installed #4 T Stat, Run 5 minutes without fan and temp is 195*, feeling the hoses the upper is now getting hot near the radiator (T Stat opened) lower is bath water warm. 5 minutes with the fan on no air and temp was 215* and climbing. Put a c clamp on the bypass hose to make it pull more water through the radiator and temp still climbing past 230*. I'm starting to think the wife has the right idea almost $600 and 1 month later. Like all the other people with these problems it used to always run 195* at all times.

How are you measuring the temperature, by the I/P cluster? Maybe the gauge is malfunctioning. Have you scanned for what the PCM thinks the ECT is at?

Just off the cluster. When it said 260* last fall it was sizzling and cracking and smelled hot. Also the coolant starts flowing through the top hose at 195*(can feel the hose getting hot after the t stat opens around that temp). Just got back from Chevrolet. they said $125 to diagnose plus parts and labor to fix it. Also had never heard of a heating problem in cavaliers. I hsve not had it scanned yet.
For now no stat, manual fan, running around below 145*. I've got a "Dodge"mechanic friend checking around for me. This is getting personal.

The thermostat (working) acts as a flow restrictor so you have some retention time in the radiator. That needs reinstalled (working)

I don't know but I've a feeling that the thermostat may be installed backwards (been there, done that). The side with the spring around the cylinder should be immersed in the hot coolant, i.e., toward the engine and not the thermostat housing.

Chevrolet has made the t stat housing idiot proof. T stat only fits one way and in one orientation, 12 oclock/ 6 oclock, guts in the hot water flow. The above mentioned tests prove the system IS capable of cooling the car. Flow was thought of with the 3,200 rpm results. Gutting the t stat showed two things, where the problem is and the rest of the system still worked. If the gutted t stat doesn't restrict enough to get to operating temp then the t stats 1-3 restricted to much causing the over heating? Went to chevrolet and bought t stat #4 last evening. Going now to install it and give it a trial run. I'm getting way to good at this. Still working on my connections to get a full scan on it also.

Yep getting better at it. Filling it with coolant as i type.

Test and retest. FAIL. Jumped to 205*, auto fan can on, drove 2 blocks and got to 235*. turn around came home and opened the radiator drain. Thought that was not much so refilled and did a retest after doing everything to get it full, ran at 205* auto fan running, crept up to 210*, drove 7 blocks and was at 235* and climbing. returning home i tried 3,200 rpm in nutral on the way, was 205* by the time i got home. Im putting the gutted t stat back in after its cooled off. At least i can get farther than a half mile from home that way. Also did a little hammering on the gutted t stat to make the hole slightly smaller.

Does the radiator have a fan shroud?

Going back through the posts. Appears the stat is working since you feel water through the top hose. I'd suggest maybe a 180 or so Tstat. You may not have a shroud on the radiator as the blade may already be shrouded (they are on my lumina). Ok, rehash, when did this start, and what circumstances where they? The fan is comming on? I am not sure what speed those are supposed to turn. When you replaced the radiator was a direct replacement? That small of an engine I'd not think it would need more than a two row core.

Electric fan is kind of shrouded, stock. New radiator was a direct replacement, two row direct bolt up. Even chevy's t stat was a 180*. Started last fall on the road between pason and phoenix doing 70 ish down the hill. Nursed it home in short hops in what became a very long trip. This car always ran 195* up hill, down hill, rain or shine, desert or snow. Replaced the 1st t stat and got along for almost a year (no trust or trips), since then nothing has worked to fix the overheating. The fan now comes on about 205*. When it over heated it was not working unless the ac was on, (it was) which was 95% of the time anyway. Radiator fan works now with all the fluid i have been running through it. I still have the manual override i can plug into the electric fan. Its not needed but was nice to use in the tests. When i did the head job the head gasket was just about plugged solid. every 5/16 hole was a pin hole at best. Cleaned up nicely. I was told the coolant had been mixed with a different brand/type. I'm chevy to the core (except for the token ford and dodge in my youth) so it didn't come from my personal supply. I'm done working on this thing unless some ones got a sure fire fix to try. Wife wants to rent the car shes got her eye on for a weekend of testing from some agency. Think i'll say yes............

I had a chance to drive down town today, 17 miles one way. Most on the freeway. Temp ran about 170* on city streets without the fan running in 4:30 heavy traffic. On the freeway the temp came down to 145* without the fan running in 5:30 heavy slow and go traffic. This thing is sucking gas like my suburban. Filled it Saturday night, 70 miles later its down more than an 1/8 of a tank of gas. Wife says she usually goes almost 100 miles before it comes off the full peg. No leaks and no gas smell. the wife's idea is sounding better all the time.

The poor gas mileage is a direct result of the under temperature condition. The PCM probably isn't even getting into the closed loop operation. You said "the head gasket was just about plugged solid." DEX-COOL mixing with regular antifreeze can create nasty gunk that'll plug up everything. How did you clean it out (I've heard Cascade works good)? Also, silicates in the regular antifreeze will coat everything and thus it's best not to go back to DEX-COOL.

I cant stop thinking about this. Is it possible LOW flow through the bypass to the back of the t stat could be letting the t stat only open part way? I need more flow threw the t stat to stay cool. Checked the gas mileage at 23 city. None of my connections have gotten back to me yet. All blockages were at the gasket, 3/32 of an inch into the head and block, block cleaned up nicely with a shop vac and screw driver, and used a rebuilt head. Dont have any idea how many times or how long i flushed it hot and cold. Wife just checked on being "Pre-approved".......

I think you SHOULD "stop thinking about this" and make her happy. Anyway, you made me read through this entire sordid thread again. One thing I don't understand is when you said "hot coolant splits somewhere and most goes through the radiator and back through the thermostat to the pump." The direction of the coolant flow should be from the hot block, through the thermostat, and toward the radiator. Either you have some weird setup or the water pump is turning the wrong way. What's the 8th of your VIN?

EinST is correct, the bottom hose supplys coollent to the engine, when up to temp, the tsat opens allowing that flow back to the radiator. Without a tstat you are not restricting the flow enough to allow the coolent enough time in the radiator to cool. The bottom hose will always have coolent in it. One ? does the bottom hose have an internal spring or is it a universal replacement? It could be it is collapsing on you. Thats ONE important thing to check. In other words does it look like one of these with the external ribs?
Radiator Hose : Flex Radiator Hose : Universal Radiator Hose

It runs 150*ish with out the t stat. Its got the stock smooth hose with the spring inside, looked good, checked it when i replaced the radiator. The hot 1" line comes from the right side of back of the of block somewhere to the external t stat housing past the spring on the t stat on to the pump. The main hot line comes from the left side of the head (a 1/2" line splits off going behind the block to where only god and gm knows where) to the radiator inlet, out to the front of the t stat and on to the pump. When the wife gets home i'll look for the vin #

Vin# 1G1JF52"4"5...... The wife laughed out loud for real when i told her you said i should make her happy. It was nice to hear her do that. Thanks we needed that.

Okay, so you have the old OHV 2.2L motor, I had to make sure. The general coolant flow is through the thermostat, the lower radiator hose, radiator, back through the upper radiator hose. The smaller diameter hose that tees off on the hot side of the thermostat is the heater hose that feeds the heater core. The other smaller diameter hose that tees off of the coolant pipe on top is the outlet side of the heater core. This setup eliminates the coolant bypass line (allows some circulation before the thermostat opens). In your case, I think the heater core is plugged up which causes no or insufficient coolant circulation to kick-start open the thermostat. Do you get any heat inside the cabin?

YOU have cleared the muddy water. Just made a Pepsi run with the heater on, eh so so. Water temp was around 150* so not great heat BUT i have an old trick to try. Saturday Ill bypass the heater core by running the Teed off top line directly back to the t stat housing and install the working t stat. If it works it is a partially plugged heater core. And i'll go on from there. Thank you for giving me hope.

It's sounding more and more like the heater core, then. One more thing, I got conflicting information from different sources and thus had to double-check on the coolant flow direction. You were correct in saying "hot coolant splits somewhere and most goes through the radiator and back through the thermostat to the pump." The coolant does flow out through the upper radiator hose, radiator, lower radiator hose, and then back in through the thermostat. What opens the thermostat is the hot coolant from the top heater hose through the heater core into the manifold inlet just behind the thermostat. I can't help but scratch my head and think how it's one of those clever but asinine designs. Keep this in mind if you decide to back-flush the heater core.

When i took the old radiator apart it looked like kitty litter stuck in the row ends, starting half way down, more as it got lower and looked totally plugged at the bottom. I can imagine what the heater core looks like. Is there a chemical flush that would help when i back flush the heater core? Or just use lots of water?

It's basically some sort of organic precipitates and thus I've heard the cascade powder or another dishwasher detergent with a tiny red ball in the middle work well. Back-flush as much of the loose stuff out first. If it doesn't work out, probably look for another car? Heater cores are usually pretty inaccessible.

Success!
Bypassing the heater core with 20" of heater hose and one of the original hoses(for the elbow)the car ran at 195* in stop and go city traffic for a 20 minute drive AFTER getting up to temp before leaving. Shut it down to shop and when i started it up after 20 minutes the temp was still good, it was creeping way up after shut down lately. This proved even a partialy plugged heater core will make this car over heat.

I back flushed the heater core using 2 12" sections of heater hose empting into a bucket to catch the bigger crud. Sent shock waves through it by kinking the hose rapidly many times. Boy did it catch crud. I mixed Cascade and Lemishine in a bucket. Both are for dishwashers and used together. Lemishine says for hard water. This works great in our dishwasher with the hard water build up we had. Filled the heater core for 1 hour and flushed with fresh water some more. Did the same with CLR and flushed. Im soaking some of the material i pulled from the old radiator in a cup of each as the heater core is soaking. After 6-8 hours i've seen nothing happen to the test material. Oh well, I still flushed the heck out of it.

I have since put everything back as it was in the beginning. After the test run its still running At 195* +- a needles width. As it did before all this started. And no creeping up in temp when shut down.

Thank you to everyone for your comments and suggestions. I hope what i have gone through and learned will help others.............
Bob W.

The one thing you want to do is make sure the cascade ect. is out as I don't know how it would react to anti freeze. Glad you got it figured out. Alot of that crud in your radiator as you described is probably from hard water getting hot (anti freeze mix). Now when you go to refill it, I'd suggest you use premix anti freeze.

Congrats, Bob.:) And, thanks for documenting the relevant details in such a thorough manner. I'm positive your experience will help others who find their way to this forum with the same root cause.

I'll have two or more days running with straight water before i before i plan to drain and fill with 50/50 mix. Arizona has VERY hard water. I have been using Reverse Osmosis water in batteries and radiators for a while now. My local contacts were puzzled so i typed in key words on the internet. I found this site and you helped me succeed.

One quick follow up on the tests 24 hours later, cascade/lemishine- still see no difference, crud is the same size and hardness (still a lot of powder not dissolved, maybe real hot water would help that). CLR- softened the crud to a 25% size reduction, the core of the crud is still hard. Vinegar- still see no difference, crud is the same size and hardness. CLR might soften any crud stuck in the system enough to be back flushed out, just dont know what prolonged contact could do in the system.

Again thank you. Bob

10/30/2013 and still running strong :)

Great Info
 

Great thread with a lot of good information.

Bad update, 7/18/14, Got hot today. Came home keeping an eye on the temp gauge and rpm's over 2,000. I'll check things out this weekend and report back.

The engine got hot and was surging at idle, and the ac didn't work at idle. First thing i did was bypass the heater core in Az in July, to eliminate that possibility in the over heating problem. After a low speed test run temp wanted to climb above normal. It looks like my radiator fan is not running. Even when the ac is on, no fan. The ac is also causing the engine to surge very bad when stopped (+1000 to 1500 rpm). The ac sounds thumpy from the high head pressure from the front coils not being cooled. It pegged my cheapy Auto Zone ac gauge. The next step is to check the fan with 12 volts and hook the heater core back up, when it cools enough to touch.

Burnt my hands and arms a little but, I was going to use the jumper switch I still had under the dash to test the fan. Pulled the switch out from under the dash an plugged it into the lighter socket. When swapping fan wire plugs, mine for theirs, Theirs was burnt on one leg. Just for giggles plugged mine in any way. The fan didn't turn on. Sounds like i need a fan and new plug.

Checked the old fan motor with an ohm meter and it showed to be an open circuit. So around $25 for a new radiator fan motor. Replaced the connector with my salvaged one. Hooked the heater core back into the system. Installed fan, coolant. Run test, around 195* fan came on holding temp. Ac turns fan on and is cold at idle and not sounding thumpy. Idle is not surging. So we are good to go.

Thanks BW56
 

I know its been sometime since this thread was in the making but just wanted to say thanks to you BW for following through to the end and coming back to update! I am also glad you didn't give in to the new car for your wife idea and abandon the project and many people like me that would read this through to the Heater core flush answer! I hope all is well with you folks and Thanks again! Now let her get that car she's wanted if you haven't already:)

Chevy Cavalier overheating problem: Answered!