QuestionHi Roland Thanks for what you do (You have already help me out once a few months back) Today the wife got home and the LHS was over heating. Opened the hood to find the coolant tank was audibly boiling and spitting water/coolant out the back. Apparently there is a small round hole on the back top of the coolant tank. (Is it suppose to be plugged with something?)
The cars temp gauge was of course maxed out and both the oil light and temp gauge were on. After a few minutes the boiling stopped and the gauge went back to normal.
The car has had a small oil leak ever since they replaced my radiator and didn't tighten down enough one of the tubes that go into the radiator. We moved right after the fix so we couldn't get them to redo their work.... but we have had no problems with that. (I just make sure to check the oil often and i end up adding about 1 qt between oil changes due to the loss... Whats you thoughts? Thanks!
AnswerThere are many reasons for overheating:
Low coolant level prior to most recent driving trip
Loss of coolant during recent trip due to: leak in hose, radiator, water pump or elsewhere in engine (such as a head gasket leak which would cause coolant loss out the tailpipe as steam or milky engine oil appearance), heater core leak to floor in cabin
Thermostat failed to open fully when temp rose
Radiator coolant passages partially blocked
Radiator air flow impeded by dirt/leaves
water pump impeller defective
dragging brake
So those are the kinds of things to look for as a cause.
There is no engine oil that goes into or in any way is involved with the radiator in most situations that I know of. If you mean a coolant leak then of course that could be the cause of this overheating if either the coolant level was low to begin with or the leak got worse during the trip. So loss of engine oil would not explain the overheating as far as I can tell.
The transmission does have a separate cooler core and so you may have a trans fluid leak which would be red in color and could be what is leaking but that would not affect the coolant system for the engine.
The system pressure exceeded the limit of the pressure cap on the overflow bottle due to the overheating and that then allowed coolant to leak out the overflow outlet. There is no plug, but usually the pressure in the system will not reach the point of exceeding the design limit of the system/pressure cap so that loss you observed was symptomatic of the overheating situation.
I would refill the system and observe for leaks. Put a 4' length of clear plastic hose on the thermostat housing bleed valve nipple and direct the hose over the front of the car to a clean container to catch the coolant as you refill the system (You don't want coolant to get on the drive belts). Then take the cap off the recovery bottle and slowly fill the coolant recovery bottle until fluid starts to flow out of the clear hose. While adding coolant slowly as necessary to keep it running from the 4" hose, gently squeeze on the top radiator hose until all the air is exhausted from the system via the bleed valve hose. The outflow from the hose should have no air showing up. Close the bleed valve and fill the system the rest of the way until it reaches the to the mark on the side of the overflow bottle. Remove the hose from the bleeder valve nipple.
There is one internal engine cooling system fault possibility for the 3.5L engine if no other cause appears to explain the overheating. There is a 'jet tube' that returns water to the thermostat housing and that tube has for some owner experienced blockage. That would result in the delayed opening of the thermostat and consequent overheating.
Roland
