Hello All,

My daughter has a 1996 Dodge Intrepid (3.5L) that is overheating. I have checked just about everything I can think of and still not able to root cause it.

Seems to overheat in stop/go traffic. Have not tried a highway run yet. This was a sudden failure not something that gradually got worse over time. Therefore, this leads me to think it is not a radiator issue, though I could be wrong here.

Anyway, here are some details.

Last year, the waterpump bearing went out so I replaced the waterpump and timing belt while I was at it. So I am confident it is not a waterpump issue.

So far, I have checked/replaced the following.

Fluid Levels: Checked, fine when cool. Losing it when it overheats/boils over.

Fan Relays in Power Box: Checked/swapped with other relays (Wiper). No improvement. Also measured resistance between terminals...measure OK.

Fuses in power box and inside compartment: Checked, both fuses OK

Hoses: Checked. Hoses seem fine.

Thermostat: Checked. Top hose is heating up after a time so I am pretty sure the t-stat is OK.

Bleed Valve on T-Stat housing: Checked. Bled air out to make sure T-Stat was not stuck closed.

Temp Sensor in T-Stat housing: Checked, seemed OK (see below)
Temp Sensor Voltage: Checked, measuring 5V.
Temp Sensor Resistance: Checked, measure decreasing resistance with increasing temp. Plus, Guage moves in reponse to rising temp.

Replaced Temp Sensor anyway with new one from store.

Radiator and Condensor fans: Checked. Both are working when connected directly battery.
Note: Fans were not coming on at idle even when temp would rise so I pulled housing out and replaced the relay switch (RFI) with a unit from pick a part. Now fans will come on once temp rises too much. However, this still did not solve problem of overheating.

Additionally, fans do not come on unless key is on and car is running. I thought they should come on when the key is on and the temp is too high, but they don't. Also, when the fans come on, they are going full bore. No ramp up/down, just all on.

Summary: So, even with full fluids, new temp sensor and replaced RFI switch on fans and fans coming on, the car still overheats in city driving within about 10-15 mins.

I don't know what else to check.

Anyone have any thoughts?

Thanks
Java

 

OK. Additional Info.

Just did a highway test and it is overheating at highway speeds as well.

Checked the air blowing from the radiator fans and it is cool air.

Thoughts?

Regards,
Java

 

Do you have cold spots on the rad, or is the entire rad cold? Your pump shaft may be slipping so you may have no flow. You may be plugged up in the rad. Have you tried to see what happens when you turn the cab heat on?

 

Thanks.

I will check the radiator tomorrow and try the heater as well. I am concerned that it may be a blown head gasket, but it is not smoking out the pipe.

 

The fans are running... but they do not come on when the car is sitting... or when the ignition is off...

The only difference is that at highway speeds... everything is OK... temps are normald. Overheating occurs in stopped traffic.

Seems to be only a fan issue... at the high setting... as they run at idle.

I also swapped out relays... and all fuses are OK.

Some type of sending unit... sensor... not telling the fans to go on high?

 

Did You check the items I asked? I suggest the basics first as they are usually the cause. As for the fan speed, unless it's smokin hot outside, even a low fan should cool enough at a idle. Start simple and go from there.

 

KurtS2...

I did not feel the radiator...

As I stated... on long trips... highway driving... the temps are OK... so the flow to the radiator CANNOT be an issue. You cannot drive on a long trip with coolant only in the block... so the radiator flow... Thermostat is OK.

 

You can have restricted flow to a percentage of it and therfore cold spots. This has the effect of using a small rad and with less airflow (at slower speeds) overtemp conditions. Did you try turning on the heat in the cab as additional cooling surface?

Now if you don't want to even try these simple checks, why do you even bother asking for ideas? If these don't pan out, I would have gone on from there, but at this point I don't feel you need any more help and you seem to have all the answers. Good luck to you sir...

Kurt

 

Not yet. Been really busy at work so today is the first chance I have had to get back on it.

Going to start on it in just a bit. Will check radiator for cold spots and report back.

It looks like a 2nd poster and I are working on similar issues. Not sure if your reply was to me or not, but will be back on project today so I will keep an eye on this thread.

 

OK. It is hard to get to most of the radiator but the first 3 inches of the radiator on the left side near the top hose (looking at car head on) are getting warm but as you move to the right is it cool to the touch. The lower radiator hose is not warm at all. Since most of the radiator is hard to get to, I can't tell if there are cold spots or not, but feeling along the top, after you move 3 inches or so to the right, it gets completely cool so I am assuming that the entire radiator moving to right is cool.

When you say the pump shaft may have slipped, I am assuming that it should not be the problem given that I replaced the water pump about a year ago. Do you think it is likely that the pump is bad already?

Also given that the top hose is getting warm and the thermostat is opening and those are both above the pump, wouldn't that mean that the pump is moving water up, it is just not getting through the radiator? Or are you thinking that the pump is just not moving as much water as it should (i.e. pumping up pressure)?

It seems to me that all signs point to radiator, but I am not sure. Should I move to flushing the radiator?

Also, best method for flushing the radiator? I have never done that one before. Is it as simple as draining radiator and filling it with water and flush material, then running for a while then drainging and replacing with anitfreeze/water mix?

Thanks for any advice.

Regards,
Jay