QuestionI have a 99 LHS with the 3.5L,115k. When driven over 4 miles the temp. gauge will go over ½ to ¾, temp 228 to 258. Turning the thermostat to 90F,fan to high & opening back windows drops gauge to ½ & fans stay on. Fans normally cycled 7/16 to 3/8. My mechanic replaced thermostat, water pump & timing belt with new from Chrysler. Radiator was dropped & flushed, it looks new. Engine block was flushed. Informed mechanic of one of your answers: if jet tube that returns water to thermostat housing experiences blockage will result in delayed opening of thermostat & overheating. He checked & found no blockage, then installed second new thermostat. He says thermostat is closing down at 220F but cannot figure out why. Between thermostats it ran without one at 150F. I do not think trapped air is an issue. He opens the air bleed & has a pressure vacuum system for charging coolant. He has 30 plus years experience. His father & grandfather ran the repair service before him. He has two quires into Chrysler. The original. water pump looked good but the timing belt needed replacement. One thing I have observed: every time we fill the left side of the overfill reservoir between the minimum & maximum marks, but when engine cools down the left side is full to the very top of the 16lb. pressure cap. The right overflow side is at the minimum level before & after. We have used two new pressure caps; the second one having the clip relief on top. Five times he has run the test for exhaust gas in the reservoir: negative. Twice he has pulled the plugs & turned it over with no sign of coolant. Looked in with a camera & all piston heads were sooty black, no sign of being cleaned by coolant. We are running out of ideas. Any suggestions will be followed up on
1st Answer to 3/12/11
Hi Bill,
Is there a possibility that you have dragging brakes? Check the wheels after driving a distance to see if any are hot? Any engine fault codes found when you cycle the key 'on-off-on-off-on and leave on" in 5 seconds or less and then watch the odometer for 4-digit codes?
The only other causes I can think of are air in the system which, when drawn to the suction side of the water pump, will delay the opening of the thermostat. As to refilling the system: When the air bleed is opened, and a hose to the front of vehicle attached to collect the overflow, do you then add coolant until a steady flow comes from the hose Are you using the separated type of filler funnel (part 8195) so coolant goes in the pressure side of the bottle and not the overflow.
Have you verified the accuracy of the temp gauge?
The fact that you haven't overheated and lost coolant means things aren't severe at this point.
Roland
I will check the wheels to see if the brakes are an issue. A hand held diagnostic reader was hooked up to the cars electrical plug “OBD” under the dash. It did not give any engine fault codes. It did read the temp. At ½ on the dash gauge as 228F and at ¾ as 258F. These temps were ballpark verified with an inferred gun. He has not followed your detailed procedure for adding coolant & bleeding air. But he assured me his equipment & procedure refills the coolant without air. I am skeptical of that. I will let him know that air drawn to the suction side of the water pump will delay opening of the thermostat. Its my only car but I had to leave it in the shop over the weekend because we went through so much to verify the head gaskets are still good and he does not want to risk me overheating it; says running it at temp gauge ½ 228F with car heater at full blast is still to hot for gaskets. I will let you know how we do next week. Thank you very much for the advice. Bill
2nd Answer to 3/12/11
Hi Bill,
The fans appear to be cycling at about the correct temps (a few degrees on either side of 230F). I don't believe there is anything wrong with running at half scale (228) routinely, or at 3/4 temporarily. I can't see any harm to the gaskets at 230.
The other possibility to check would be that a build up of debris on the fins of the radiator or the oil cooler is impairing the air flow and thus the dissipation of heat. So try to get a light behind them and look through the grill to see. Let me know if you find something interesting.
Roland
At 230F [1/2 on temp gauge] the fans are not cycling but staying on constantly. The fans came on at 7/16’s [about 220F] and shut off at 3/8’s [about 190F] on the temp gauge when they were cycling. If the engine is started and ran at a stand still idle the fans will cycle between 7/16 and 3/8 on the temp gauge. When the car is driven at 30 to 50 MPH the temp gauge will go up to ¾ [about 260F] at which time we put the inside heater on at full blast with windows open to cool the engine down to ½ [about 230F] and fans stay constantly on. Bringing the car to a stand still idle now will not lower the temp below ½ and the fans will stay constantly on. When the radiator was dropped we cleaned the fins of the radiator and oil cooler with compressed air. I will let you know how we do next week. Again Thank You. Bill
Dear Roland : The above is what I conversed with you on 3/12/11. Since then we have replaced out the radiator and the thermostat opens at 180-190 and when coolant temperature gets up to 250-260 the thermostat closes down !! A mechanic friend of my mechanic, from Indiana says it is due to a dime size channel in the head that is plugged with metal corrosion. We are running it now WITHOUT the thermostat at 170 hopping the corrosion will work lose. He says we have to take the heads off and clean the plug. Have you heard of this narrow channel in the head being blocked with metal oxides causing overheating before and if so any ideas on how to clear it without the expense of taking the heads off? Is there a spot on the head that tapping with a metal rod & hammer might break it lose. Would taking the hoses off the radiator & reverse flushing water into the top of the block and out the bottom break the corrosion lose? I thought maybe drilling two small slanted holes in the thermostat would cause just enough turbulence to keep it from closing. The brakes are not dragging . It has 115K, new tires, new front rotters & new pads ; is clean and runs nice. Any help or advice will be appreciated. Thank you Bill.
AnswerHi Bill,
I can't recall any specific report about such a problem with the 3.2 or 3.5L engines. I know there was an issue with oil passageways closing down on the 2.7L in its earlier years of production but that is an entirely different unit from your 3.5L. May I suggest that you ask Russell Leitheuser the question (along with the history of course) as he has worked at Chrysler dealers and may therefor be familiar with this situation. He very recently volunteered to serve here at AllExperts and I am pleased to have him 'on board'.
Roland
PS There is one further possibility to consider:
"The OEM thermostat is staked in place at the factory. To ensure proper seating of replacement thermostat carefully remove the bulged metal from the thermostat housing using a suitable handheld grinder. It is not necessary to restake the replacement thermostat." (2004 Chrysler shop manual).
Perhaps this needs to be done for the thermostat you had in there to function properly.
