97 Intrepid overheating

The check engine light has not come on, on this car, just my other Intrepid (and it was code 43). This Intrepid has the intermittent over heating problem. As explained in the other post, the code 43 was due to a misfired cylinder and a leaky intake manifold.

My chellenge is with this Intrepid (same year and a 3.5L engine too). Any thoughts? Mark Devoted Chysler Customer

I am running out of things to try (to fix the overheating problem), so I am going to try removing the t'stat to test and see if the car still overheats. I realize it will affect my mileage and engine performance, but it may be worth it to test for a few days to see if I purchased and installed (a second) defective t'stat.

Quick summary:

1) Car over heated this winter due to low coolant. 2) I was travelling so I only had the garage replace the t'stat and they checked for leaks (they thought there was, but could not locate it). 3) Went to my garage and they found a leak in the water pump and replaced it. 4) Car worked fine initially, but later, intermittently pushed antifreeze out the overflow. 5) Garage gave me some system flush chemical to try and clean any rust out of the system. 6) Found a service bulletin on bleeding the air out and did that. Worked ok for a while with only a couple times pushing antifreeze out the overflow. 7) Last few days repeatedly has started pushing water out the overflow basically after driving just enough miles for the car to come up to temp (after the car is shut off).

Other facts: - Temperature registers 1/4 temp on the guage at travelling speed (vs. 1/2 guage temp on my other Intrepid).

- Fans are coming on when temperature climbs above 1/4 on the temp guage (when not moving / stopped at an idle) and holds between 1/4 & 1/2 on guage.

- Heat comes out of heater so flow there is apparent.

- Car was pressure tested for leaks (after water pump replaced) with none found and I have not seen any subsequent leaks.

- Have tried swapping rad cap with my other Intrepid (no difference).

- Now running basically with pure water, since I cannot afford continued replacement of antifreeze. (glad the freezing weather is past us)

Other thoughts:

- I have Chrysler's 1-800 number and may try calling.

- Could there be a head gasket leak causing air to be pushed into the cooling system and/or excessive pressure to build up in the cooling system? If yes, wouldn't the air just push into the overflow reservoir?

- Any other thoughts or suggestions?

Mark

Hi Mark...

Not a mechanic, just a retired old electrical guy who loves cars. Take my guesses as no more than feeble attempts at common sense guesses, please.

You mentioned flushing the cooling system, but I wonder if there's any possibility that the rad is really good and plugged up, perhaps to the point that it should be replaced? Possible a previous owner or garage filled it up with bars leaks or something similar?

And have you felt the hoses? (the big ones on the rad). Soft and squishy, perhaps collapsing under some circumstances?

Just thoughts for whatever they may be worth :)

Take care.

Ken

Good thoughts Ken!

In response: If the rad was partially plugged, I would have expected the temperature (guage reading) to increase, but it only does that if my coolant level gets too low (and thus truely forcing the engine to overheat). Anytime there is sufficient coolant, the temperature guage remains within the noremal 1/4 to

1/2 ranges (normal operating temperature). I thought maybe the temperature guage may be out of calibration and showing a lower than actual temperature, but the rad fans will cycle on and off as it approaches the 1/2 way point on the guage. So unless the rad fans use the same sensor as the temerature guage, the rad fans cyclying should indicate the engine is operating at normal temperature. I have a service manual and will check to see if they could use be using the same sensor.

The rad hose (at least the upper one) can be squished fairly easily and I had thought of this too, but short of replacing them to eliminate the potential I am not sure how I can test the hose strength. I have monitored the hoses at idle, but saw no collapsing. If they are happening at a higher RPM or while driving it could be a possible cause maybe. Any suggestions how I can test? It almost appears that under driving conditions everything is ok, and that the coolant is only expelled after the car is shut off (which is why I have tried different rad caps). This leads me to believe that the coolant flow may be restricted somewhere in the block after the t'stat and temerature sensor (forcing it to travel more through a bypass) and thus giving a false reading.

I just got back from a trip into town (10 miles each way), and the temperature rose as expected and remained normal and there was no coolant being expelled out the overflow in town or at home. I will go out and recheck now in case the pressure just had not built up enough yet.

Mark

Have you got a good radiator cap? Is it the type with a spring-loaded check valve (the little metal disk in the center of the gasket) instead of the free-hanging type? Its been my expereince that either a weak cap or one with the free-hanging check valve (made for a traditional "coolant recovery tank" system where the overflow bottle isn't pressurized) will cause coolant loss and eventual overheating in a first-gen 3.5.

Mark wrote:

It is a pressurized, spring loaded rad cap, and I switched rad caps with my other Intrepid that is the same year and has the same size 3.5L motor (which does not have this problem) and the overheating problem remains with the car (not the rad cap). So I have to assume the rad cap is not the problem.

Mark

If the thing is properly bled and the antifreeze ratio is correct and you have replaced the radiator cap, and it's blowing coolant out the overflow I would start checking for the presense of water in the engine oil, oil in the antifreeze, and water coming out of the exhaust. (not condensation) All signs of a failed head gasket. And it's easy to ruin a head gasket when you overheat then try limping into a garage.

Ted

I had thought about the head gasket and have been montoring the oil, and have never noticed water or excessive condensation dripping from the tail pipe, nor have I seen any contamination of the coolant (now just plain water).

Now I have driven the car a couple times, two seperate days, 10 to 20 miles each day with both sufficient to bring the car up to temperature and neither times it has over heated or even spit any water out the reservoir overflow. The level has remained good. This overheating problem has been intermittent (where it will work fine for days or weeks, then all of a sudden start pushing out the coolant). I am still running with the rad cap from my other Intriped, so again I do not believe it to be that (the other car has never overheated with it), because I thought it might have been an intermittent failure of the rad cap. Are there any other things that could be prone to an intermittent failure (besides the t'stat which I have already replaced)?

Mark

Cooling fan relay?

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

I do not think it would be the cooling fan relay, as the fans do come on anytime the temperature rises (on the guarge) between 1/4 and 1/2 point (e.g. if stopped for any length of time at a light and just sitting idling in park). The temperature usually sits at or around the quarter mark on the guage when moving (vs. the half way mark on my other Intrepid). I had suspicions about the guage reading, thinking maybe it was just reading low relative to the actual engine temperature, but it does appear to be fairly acurate by the fact the fans come on when approaching the halfway point.

The problem is almost as if there is a bit of a coolant restriction within the block itself and/or when the coolant temperature at the t'stat and sensors rise to the correct operating temperature, a bypass permits the coolant to flow more through it than the engine block itself. Could there possibly be a restrictor missing in a bypass permitting more coolant to pass through it than the t'stat?

Mark

You said the problem is intermittent. What the fans (or whatever is causing the problem) do when everything is operating normally (i.e., not overheating) doesn't mean a thing. I was suggesting an intermittent fan relay.

Let's try this again: When it does overheat, you have absolutely verified that the fans are running *at* *that* *time*?

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

The fans reliably will come on when the temperature guage reaches between

1/4 and 1/2 on the guage and/or I turn on the air conditioner.

The reason I describe the problem as intermittent, is because the overheating may occur any time. I have found nothing consistent that I can relate to a cause for over heating (distance travelled, type of driving such as highway or in town, ambient outside temperature, etc.).

The problem is starting to occur more frequently now though, as it has happend twice now this week (and have driven the car at least once per day). Sometimes the car would work fine for a month and not over heat, but now with the problem possibly starting to happen more frequently and the weather getting warmer, maybe the overheating problem is partially related to the ambient temperature.

I have been considering removing the t'stat from the system for a week or so (or until I learn what the effect is) to see what happens. I realize this is not good for engine performance, but unless anyone has other suggestions, I am not sure what else I can try.

Mark

Hi Mark...

Looks like I'm about to join you with cooling problems (leakage), so I've been thinking a bit about this...

Is it possible that this is really a heads-up that your belt is at risk? I'm sure I read back a piece that you'd replaced the water pump, and guess that the belt would have been changed at the same time? The tensioner?

Anyway, what runs through my mind is that the crank/cams are driven by the toothed side of the belt, right? A little sloppiness here might be temporarily forgiven given the teeth.

But the water pump is driven by the smooth side of the belt, where a little sloppiness could far more easily let the pump stop turning (or turn more slowly, or perhaps "stick" intermittently. Perhaps worse, if the water pump is weeping just a little, it might even tend to "lubricate" the belt - affecting the smooth side most.

Hopefully the mechanics here will tell us whether or not this theory holds water (arghh :)

Take care.

Ken

Hi Ken,

I just checked the invoice for when they (my local garage) replaced the water pump (last December) and yes they had also replaced the belt at the same time (and also the temperature sensor too). I would expect they re-adjusted the belt and checked tensioner when this was done, but will ask them next week.

I called the garage this morning to let them know the problem still exists and discuss possible next steps, and they said it should not hurt to remove the t'stat for a period of time to test the functionality (running without it), and the mechanic indicated they have a solution to put into the coolant to test for head gasket leaks. Apparently the solution changes colour if there is and head gasket leakage due to firing or emissions into the coolant.

This coming Tuesday I am planning to go see them and have the solution added, and if I get the t'stat out and see how it works prior to then, I will post an update.

I have the service manual for my car and have read everything in the cooling system section from beginning to end (other than the missing service bulletin regarding bleeding the system with a special aid that was issued later (which I now have a copy of). Everything points to the symptom description in the bulletin...temperature guage reads low, heater core temperature not as hot as it should be, but even when I bleed it by overflowing the reservoir until no more air comes out the bleed valve, the problem returns. Mabe I do have a head gasket leak that is pushing air back into the system.?????????? Hopefully I will know next week!

You mention water pump weeping just a little...There is a section in the service manual regarding a weep hole (black stain on the water pump body), but apparently it is normal for a little to weep out (according to the book).. There is a bit more on this in the book, but I am sure your garage has the same or something similar. Good luck with you problem, and please keep me posted.

Mark

Or it only happens when the fans AREN'T working right? i think that was Bill's point. The fact that they operate consistently when sitting in the driveway does NOT mean that they happen to be operating when the engine is overheating.

I believe I understand what you and Bill are saying, but to my knowledge, turning the air conditioning on over-rides the temperature sensor and forces the fans on all the time. At least it does sitting in the driveway with the car at any temeperature (hot or cold), and I thought I had read this somewhere in the service manual too.

Now if I am incorrect and/or for some reason they are failing during driving, it will be very difficult to check unless I hook up some sort of monitoring system. Short of replacing the fans (to see it it does make a difference), any suggestions as to how else I can test and hopefully eliminate them as the problem?

Mark

Well, the fan is turned on EITHER by high coolant temperature OR by the AC high-side pressure exceeding a set threshold.

Quick-and-dirty would be to pull over the next time the guage is showing overheat, pop the hood, and see if they're running.