Just picked up a 2001 with 144k on it. I was told at some point it had a radiator leak and the owner put stop leak in & replaced hoses. I drove it about 1000 miles no problem then it overheated. I had a flow test and flush, no problem -good flow and I drove for 3 days w/ no problem.
Today the temp went up over the white zone but not overheating or red light. No sign of coolant in the oil, find no visable signs of head gasket problems, fan has resistance. I do hear what sounds like running water from the heater box.

Any one ever see this before?

 

Stop driving it, you should get all the crap, stop leak, out of the system by flushing it, refill with water, bleed the system and have it pressure tested in that order. Once you do that you can start repairing it, most likely a new radiator and t/stat and prey you haven't blown a head gasket or worse.

 

In addition to Mike's advice, if you are using a mechanic not familiar with a D2, here are a couple of points:

1. The thermostat is "in the plumbing" and has four small holes in the flange that holds it. They must be clear of junk for proper operation. Stopz Leekz could easily have plugged that.

2. The gauge you are watching is an idiot light with a pointer. The ECU reads the coolant temp sensor, and sends a signal to make the "meter" stay at about 9:00 for a wide range of temps. Once the computer decides to move the pointer up, you are already at the high limit of normal operation and have started over heating. Don't think that it is just easing up a little. Have shop check with a data reading scanner to get real temps from the ECU.

 

Thanks Mike
I did all that. the radiator had good flow but I did not replace t/stat have you seen then stick? See no sign of head gasket leakage what the best test for that?

 

Stop leekz can make a stat stick, because when it is closed the chemical tries to seal up every crack. But once you purge system of air bubbles, you can do a pressure test of the cooling system. Beyond that, there is a chemical test for combustion gas in coolant, about $35 from auto parts store. Don't buy test uintil you have purged air from system.

 

It does sound like he's got air in the system.

 

And that is a bigger problem on a D2 because of how the stat is positioned. If the bypass holes adjacent to it are blocked, the stat may get hot air instead of hot water, and not open at the right point.

From the RAVE:

Hot coolant from the engine passes from the by-pass pipe through four sensing holes in the flow valve into a tube surrounding 90% of the thermostat sensitive area. Cold coolant returning from the engine, cooled by the radiator conducts through 10% of the sensitive area.

 

I have an 03 with 122K miles. I had to repl the TSTAT a little while back. It is plastic, looks like a big heart and had just dried out and was cracked and not allowing coolant flow in. Part was cheap, but labor was not. That would be my suggestion. Intermittent overheating, smelling hot, then finally one day (thankfully not far from work) temp gauge maxed out and then dropped flat on cold. I got off the road quick and let it cool down and got it to a shop ASAP. That fixed the problem real quick.

 

I have replaced the thermostat new, new water pump, flow tested good, flushed system removed as much stop leak as I could and the problem went away for a bit would start in the first 5 minites temp went up rev the moter then temp droped back and was fine for the day, but as of today it can back when you place your hand on the top hose going into the thermostat its hot, exit hose going back into the lower radiator port is cold, looks like no flow through the stat after 10 minites (overheats) has any one seen this happen the stat is only a 2 weeks old. Heads have been inspected find no signs of leakage. Any help would be great.

 

OK,

When I flushed my rad the first time, I had the same problem. Thermostat wouldn't open on idle and truck wants to overheat at the same time. And like you said, once you rev the engine you notice that the fluid in the reservoir goes down but at the same time fan cools the rad and thermostat cannot open. It drove me insane!!!!!
I tool a plastic cover (from the storage bin) and inserted it between the rad and the fan (after I removed top plastic cover that holds upper rad hose). This way the fan cannot cool the rad and the thermostat can now open.

It worked like a champ but you need to be careful because the fan wants to suck whatever you put in front of it.

This worked for me anyways.

Good luck and if you decide to go this way, be careful!!!!!!