Basic info.
1998 RS, with 130K miles, manual.

About a month ago, the coolant line to the throttle body cracked. Nursed it home (took a stop). Replaced line and coolant.

Drove it around a few days, and then noticed steam was shooting out. Found out the radiator cap had broken in pieced. Replace that and was on the road again.

Drove down to key west (3 hrs way), and while I was down there I noticed the radiator filler kneck had cracked. Picked up some JB weld, patch the crack, and was about to get home with any overheating or significant loss of coolant. So, I repaced the radiator with an Autozone one. The core was thicker than OEM, and it had a compartment for the tranny oil cooler. I asked the clerk about it, and he assured me it was ok. Fittment was good.

I took a 20 min drive on the freeway, and didn't notice any temp issues. As I got off, the temp shot up. Ask my local auto parts store clerk, and he suggested I replace the thermostat (since it had never been done before). So, I did that.

Here's what I've observed recently. I was making a 1 hr trip yesterday, driving on freeway, I wouldn't have an issue. But soon as I turn on the ac, the ac would work fine for a bit, and then suddenly would blow hot. And following this, the temps would rise. I pulled over, and the reservior fluid was boiling.

Let it cool down and bit, canceled by trip and headed back. I didn't turn on the ac. But the temperatures would still creep up. Soon as it got to a point I didn't like, I turned on the heater full blast, and it temps would drop.

Prior to this, there was an issue with cooling on the freeway, even when the ac was blowing hot.

Things I've check.
Bled the system several time during the course of these events.
Both fan are blowing.
The thermostat is work (lower hose does get hot).
There isn't any white smoke blowing out. While reving the engine to see if any bubbles in the radiator fluid (HG check).

Anything else I can check easily? I'm in a middle of a move up to NC. All my stuff is in storage, but I do have some basic tools.

 

Here's a small update... thought I do some testing on the road today.

I'm driving to the store, about 15 miles way.

1st leg, I took the the slower path (35-45 mph) until destination. Temps gauge stayed at 1/3 for the trip.

2nd leg, returning from store... took the freeway, no ac, speed at 70 mpg. Temps stayed at 1/3 for the trip.

3rd leg, reverse path on free way with ac on. Temps stayed at 1/3 scale, until I got off. Temps started to climp to 2/3rds. I had turned off the ac when we got off the freeway, b/c it started to blow warm. Pulled into the parking lot, and let idle. It eventually came back down to 1/3rds.

4rd leg, jumped on the freeway. No ac. Temps sat at 1/3rd while on the freeway. Then when I got off it started to climb. It got to about 2/3rds, but eventually hovered around 1/2. I pulled into the driveway, and let idle. It eventually settled to 1/3rd.

Am I missing something?

One small other detail about the setup. I've got a turbo. Would the extra thickness of the autozone radiator cause this problem? I'm thinking extra thickness would put the radiator closer to the turbo. Extra, meaning 1/4-1/2"... I didnt measure, and I only recall thinking it being thicker.

 

If both fans are working (and are coming on when they should!), then what you describe sounds suspiciously like a failed head gasket.

For the next little while, check the rad fluid level regularly. Do this after the engine is stone-cold (3-4 hours or overnight). Is it always right up the rad-filler neck, or is there ever a bit of air in there?

Next time the overheating happens while driving, immediately pull over and SLOWLY turn the rad cap while pushing down on it. Keep your hand and fingers FLAT, and use the palm to turn the cap. When the cap is turned all the way to the left, SLOWLY release pressure on the cap. Does coolant begin to spurt out? ...Or nothing at all?

 

The A/C would put extra "load" on the engine, the condensor will also get hot, being in front of the rad, air flow through the rad would be hotter with A/C on then with it off, also at higher speeds airflow is better at lower speeds airflow is dependent on the rad and condensor fans, only the rad fan would be running unless A/C is on.

The turbo could be contributing to the over heating.

Question, are they still the stock rad and condensor fans and are the still on the engine side of rad and condensor??

Insure rad and condensor fans are running in the correct direction, either pulling air through rad and condensor if on engine side or pushing air through rad and condensor if they are on the outside.

One other thing to check is the water pump, the car is more thn 10 years old, if pump has not been replaced yet, it may be time. 94

 

have you tried to burp the system?

 

thanks for all the responses guys. let me try to address them all.

in regards to the hg. i'll pay closer attention to the coolant level. i hadn't notice significant loss, but i'll be more attentive. but like i mentioned, there isn't white smoke shutting out, and i didn't see any bubbles when reving the engine. i'll try something more conclusive when i get settled at my new place. anyone in the charlotte, nc area??? i won't have a garage at my apartment complex for several months.

regarding the fans, they are in the same orientation prior to my heating problem. they're 16" slim fans i got from a seller here, as i recall. the condenser fan is located in front of the condenser. and the rad fan is back of the radiator.

the water pump was replaced with the timing belt, about @90K. what are other symtoms of a bad pump? i'll look into it more.

i've bled the system many times over the course of these issues. i can do it again.

 

bump im having the same issue even with the a/c **** man i was going to replace my thermo but now hesitant

 

The problem may be the fans facing each other, [if they are] although a "pull/push" fan system can work, more often then not you end up with less airflow then with just one fan, either pushing or pulling, it has to do with a vortex effect it is possible the new rad configuration, [thicker] is causing the problem, as it is the only thing that has changed and problem seems only to be there when condensor fan is pushing air and the rad fan is pulling air, poor airflow would result in over heating and poor A/C output, A/C head pressures over 200PSI will result in poor cooling as head pressure rises, A/C output will get "hotter", you should not run your A/C until problem is solved, not just because of the overheating but excessively high A/C head pressure WILL damage the A/C system.

I assume rad fan is on the pass. side of rad, [like stock rad fan is] so question is, is the condensor fan also on pass. side of condensor, [pushing into the rad fan]?

If so, and if possible, move condensor fan to the drivers side, so fans are "offset".

We run into this problem on hot rods fairly often, rad fan is a belt driven mechanical unit off the engine, often a "beefed up" big block and A/C has been added to the hot rod and an electric condensor fan has been added in front of condensor that turns on when A/C is turned on, often this will cause the vortex effect resulting in engine overheating when A/C is on, most of the time we replace the belt driven fan with one or two electric fans either pushing or pulling air, problem is always solved, even if just one electric fan is used, set up to turn on when engine temp. is up and anytime A/C is on, in some cases we will install a pressure switch to trigger the condensor fan only when A/C head pressure hits 175-200PSI, for optimum A/C operation. 94

 

That's an interesting idea.

the condensor fan in on the driverside, and sit on the condensor (forward side). the rad fan is on the passengerside, against the radiator (aft side).

I'm hoping there aren't any hot days for a while. Today was a nice balmy 55F. And no overheating to be had.

 

So they are already "offset", then the vortex effect should not be happening.

Back to a possible problem with the new rad, as it was the only thing changed, [I am assuming].

Have you checked to see if there is possibly a "restriction/blockage" in the rad, [coolent]or through the rad, [airflow]? 94

 

thanks again from the response, fcm.

i've inspected the radiator, and did not see anything that would block the air flow. and i was tempted to drain the coolant and inspect it, but i ran out of time.

on my drive back to charlotte (1.5hr drive), at ~65F ambient, i didn't get any heatups while driving on the freeway. i did notice it spike up once... i had pulled off to a rest area. and while getting on i sped up to get into traffic. and this is the odd part, several minutes aft speeding up the temps rose to about 2/3rds on the gauge. I promptly cranked the heater full blast, and the temps dropped. the temps didn't rise immediately.

anyway, i haven't not seen any overheating since. but then agian, the weather has been mild.

i'll keep an eye on it, and the coolant levels. not having a garage really hamper things.