I just got my 2004 DTS back from the dealership today after having the case halves done and a new HG. Head bolts were not pulling just a blown HG. Drove home and it drive great , no check engine light , no DIC codes . Go to drive to store later that night and the check coolant light came on again as my car was drinking coolant before the repair and that message was on constantly. It only came on for a minute and there was coolant in the tank but a bit under the fill line. What could be the problem now or was the problem all along ?
You do a block test? You can try that. That should confirm if you are leaking exhaust gasses into the coolant lines. That will at least put your mind at ease if it is the heads going again or not.
Otherwise I mean you could have a small residual leak at the crossover, or one of the rear steel lines may have rusted out and is dripping on the exhaust.
To put it plainly, there are plenty of places for coolant to drip to and not hit the ground. So don't get nervous that the heads are bad again.
Yes definitely do a block test. It's a free loan a tool from AutoZone. If there was any external leak you can usually always smell it. Any tiny leak in mine I can smell it right away. If you open the hood when you've just shut it off and it's warmed up and you don't smell it at all, then you probably don't have any external leak. Squeeze that upper radiator hose (with hand protection) when it's hot. Is it REALLY firm? That's not a good sign if it is.
IF the surge tank pressure cap is in good condition and will hold the set 16 psi of system pressure (18 on later engines) that upper radiator hose will be pretty hard at normal operating temps - 185 - 210. If the surge tank level, cold, is correct and there is no exhaust gas seeping into the coolant then the coolant should not blow out the overflow.
Remember, 16-18 psi is the maximum pressure before the cap vents. I'm not sure what the normal operating pressure is, but I'm sure it is well below that.
Great, at least you found the problem. I'm dealing with a small mystery leak myself. Just curious, how many miles you have on it?
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