96 Deville overheating
 

Hello all,

as you can see this is my first time posting on this forum. I have read quite a few post so I will try to include all the information. I drive a 96 Deville w/ 4.6 Northstar engine. I have only owned this car for two months so I don't know much about it's history. When I bought the car Service ride control was in the display. After reading I found that the struts were bad. Now my cars is overheating my normal range was between 197 to 210. Now the car overheats to the point where is says idle engine before I shut it down. This occurs only while driving and after drivng 30 minutes or more if the car was cold prior todriving. I have to constantly add coolant but cannot find any leaks. My engine idles smooth and I have no steam from the exhuast (but there is a little moisture and a drop or two of what I think is water may fall every now and then, and I can smell the faint smell of antifreeze sometimes in the engine compartment (could be from spillage?). I traced all the collant hoses I fould locate and all were hot. Fans workon high and low speeds. and I do have heat, Sometimes when it overheats the coolant spills out the hose beneath the pressure cap but I can't say this is the case all the time. I checked the codes and Here is what I have PC1258, RS0061, PZ2042. What do they mean? I've read in other post that the problem I am having is likely to be head gasket lifted. What do you think. Forgot to tell you therostat has been replaced, system was flushed by dealership.

RE: 96 Deville overheating
 

I could find only P1258 in the '97 books, and it's related to your overheating: Engine Metal Overtemperature Protection. It turns the SES MIL "On" and runs the engine in Alternating 4 Cyl. Mode.

You've said that you are losing coolant, the engine overheats and the dealer flushed the cooling system and replaced the thermostat.

How often and how much coolant needs to be added? When did this start happening? If it started right after the dealer had changed the thermostat, I'd suspect a faulty tstsat.

First order of business would be to find the "leak". In case of gasket failures coolant leaks inside, into the combustion chamber and/or to the crank case. You don't see excessive, coolant smelling white exhaust, and this is good. The appearance of a few drops of condensation at the tip of the tail-pipes is normal. Pull up the Oil dipstick and check the coating on the tip. If it's milky or gooey, that means trouble and let us not assume that that's the case for the time being.

You can have a pin-hole in one of the rubber hoses near the exhaust manifold which only opens up when the system gets pressurized, and the coolant instantly evaporates on the hot manifold, or the coolant just drips down to the road while you drive -- not easy to find just by looking. The surest way to locate the leak, whether it's internal or external, is to have the system pressurized by a hand-held pump with a gage attached. The dealer or any competent (radiator) shop can do it.

It is also possible that the only "leak" is thru the surge tank cap's relief valve, because coolant does not flow thru the radiator for some reason. In a normally operating system (after a full warm-up) the temperature of the lower and upper radiator hoses is about the same, at least to the touch; however, when there is no circulation (due to a stuck tstat), the upper hose should "feel" much hotter.

You can check the oil and do the hose temp-check-by-touch, yourself, and then have the pressure test done. Hopefully, it is as simple as a bad tstat...

RE: 96 Deville overheating
 

you have probably seen the FAQ, but just in case,
this is it


FAQ Headgasket Failure

RE: 96 Deville overheating
 

newboot,
it's sounds like your head gasket or your heater coil. Go and get your engine pressure checked.
EX

RE: 96 Deville overheating
 

check your heater core hoses when your car is at operating temp. if one is much hotter than the other one your heater core is plugged. I had 1998 deville 4.6 that no one could solve the overheating problem in after changing water pump, radiator, thermostat, had it flushed it still over heated. everyone said it was more than likely the head gasket, but it wasn't using fluid. as my last resort I unhooked the lower heater core hose and bypassed the heater core to see if it would solve my problem, IT DID ! For some reason if the heater core is plugged it doesn't allow the coolant to circulate properly in the engine, causing it to overheat. You can bypass the heater core by removing both hoses off of the heater core and connecting them together with copper pipe or plastic coupler, it's the easiest way to see if it solves your problem, if it does then replace your heater core.

RE: 96 Deville overheating
 

big b, the OP said he had heat.

RE: 96 Deville overheating
 

Sometimes the heater core will intermitantly clogg, so check the heater core hoses when your engine first overheats.

Check lower hose
 

One problem on 4.6 and 4.9 is the lower radiator hose has a tendacy to bend in a 90 degree turn and cutting off flow to motor. This happens on most case scenerios. Easy fix, and easy to see if thats the problem. If bent near in half..thats your problem.