2006 Caravan SE, 86,000 miles; and it gets regular maintenance and checkups. Last week, the temperature gauge started acting up. Every day since last Thursday, when the van is started for the first time (or if it's been sitting for at least 2 or 3 hours), the temperature gauge doesn't move. Then after about 2 minutes of driving, it slowly moves up to normal setting (goes to halfway in about 30 seconds); then after about another minute of driving, it quickly moves to the H setting and the temperature sensor light comes on along with the warning bell.

Obviously the van isn't overheating after 3-4 minutes of driving, so we stop the van, turn off the engine for no more than 30 seconds. Restart...and all is normal, including gauge operation and readings. We can drive the rest of the day with no issues...UNLESS the van sits for longer than 2-3 hours.

This scenario has happened for 6 straight days. Took to regular mechanic second day. They tested radiator (inpection, pressure check etc.) and found no overheating or leaks. They were unable to test cluster or sensors so suggested we take it dealer. Took to the dealer 2 days later. They ONLY tested visually and did pressure check...and they claim there is coolant leaking (visibly) and that pressure-check showed it's leaking. They could not duplicate the gauge problem and did not check anything electrical. When I told them our regular mechanic found NO visible leaks and their pressure check passed, they got defensive. I asked if they checked cluster and coolant sensor and they said "no" that they're sure it's leaking and only repair is complete radiator replacement at nearly $600.

I'm suspicious, especially when a VERY trusted mechanic told us that there was no leak either visibly or through a pressure check. I paid the dealer's fee for checking the vehicle and am taking it back to our regular mechanic.

Any thoughts or suggestions here? I've talked to other mechanics and they all said dealer should've first checked to make sure the gauge is working correctly before jumping to the conclusion that it's leaking coolant, especially considering the guage issue CANNOT and does not occur once the car is running....even if it sits for as long as 90-120 minutes the gauge will not malfunction again. It only happens if it sits for at least 2 hours and usually much longer.

 

Do you know if the water pump has ever been replaced? If it has then you may have gotten a pump with a plastic empeller and it could be slipping on the shaft. I had a somewhat similar problem and would up replacing the sending unit to the gage, the thermostat, hoses and then pulled the water pump last.

A slow leak in the cooling system would not cause the problem you are having.

 

Water pump was replaced within last year. I'll suggest this to our regular mechanic. And on the slow leak...that's exactly what I told the service advisor at the dealer....that the symptoms we were having didn't match their diagnosis.

Thanks for your reply. Any other theories out there? I've gotten responses on other forums that mostly suggest testing coolant temperature gauge first to make sure the readings we're getting on first start are true.

 

Look through "TIZZY1 and others DIY info" at the top of the forum. Look for the instrument cluster self test. It will verify the gauge is good. Sensors can be had for $15 - $20. Might consider slapping one in.

 

Did diagnostic test...everything passed. Checked under vehicle before driving it for first time today. Nothing leaking that I could see or feel running hand all along bottom plastic guarding radiator as well as nothing I could feel or see up under that. Took it for first drive of day and this time temp gauge did NOT act up....with everything displaying normally. Got back to house, crawled underneath and there IS something leaking. Plastic guard just below radiator has reddish fluid on it and a slight drip coming down. If I'm facing the front of the van, it's coming from the left (about even with where the radiator cap is above). As vehicle cooled...the leak slowed then pretty much stopped.

I reread the printout from our dealer and it indicates "overflow tank was empty and radiator was 1/2 full." They added water to "top it off." Service advisor did not tell me that when I was there and I didn't bother to read the printout/receipt until I test drove it today.

What I don't understand is the gauge behavior. Was it indicating we were low on fluid but not overheating? Both regular mechanic and dealer confirmed it was NOT overheating. Temps were in normal range. I'm still not convinced it's the radiator but I am OK with eating crow if it is. Just don't understand how regular mechanic could have missed this leak....unless of course it wasn't doing it when he had it in his shop?? Also not sure how he could've missed low coolant level as he checks fluid levels anytime we have it serviced. We just had oil changed two weeks ago, (with other fluid checks), then had it in last Friday for the current problem. Dealer looked at it yesterday, so three days in between checks.

 

well... just check your coolant level every 3 days, and top off your coolants in the Radiator and overflow bottle when cold. Drive it for few weeks like this, and see the temp gauge problem acts up again. If keeping the radiator full eliminates your problem, then your dealer is probably right, there is a leak.

I think your dealer got a horrible Service advisor... If he insist the leak is the problem, he should have brought you into the shop and show you the leak with their mechanic. I also think your service writer simply didn't tell you story right to his mechanic in the first place.

 

We already have an appointment tomorrow with regular mechanic...and have a long trip on Saturday for a family function. So I can't risk it with 2 young kids in car. Need to get it fixed or at least accurately diagnosed and determine if safe to drive on a 2-3 hour trip (one way) without fear of getting stuck somewhere on the road. Will relay all info to regular mechanic so he's got good info to work with from the start.

 

Forgot to ask... is it possible for mechanic to test for a faulty water pump without pulling it?

I want to understand what our regular mechanic should be doing to ensure he finds the source of the leak so we replace the right part. I don't want to end up replacing BOTH the water pump and the radiator if they get it wrong. I can't afford both at the moment.

That's what bugged me about the dealer and why I took it elsewhere. I kept asking service writer if he was sure radiator was leaking and he kept answering, "it's the only place the fluid could be coming from." I'm certainly no expert and I stopped working on my own cars years ago...(used to do a lot of my own service work) but I'm pretty sure that's not accurate.

 

Not really, To inpect the blades you need to remove the pump. How is the t-stat?

 

To update this old thread....our problem DID turn out to be the radiator. After several days, the leak did show up visually on the underside of the vehicle and we ended up replacing the radiator. So I have to eat crow and admit the dealer was right on this one.