I have a 2015 suburban, automatic with no codes and 80,000 miles. Had it since 2014, lately the oil guage started to fluctuate on acceleration and coolant will not get up to temp. Happened at the same time, under warranty. Dealer replaced oil pump claiming it was sticking open allowing up to 100 psi on mechanical reading. The oil gauge never moved off 40 psi for 6 years till coolant temp dropped. Pressure check on cooling system shows a slow leak, sprayed down every connection and no bubbles, can't find coolant leak. No leaks seen, no drips. Any ideas?
Any sign of water in the oil?
Thin oil can cause oil pressure problem.
@cj1
It was after an oil change that it started happening. OEM filter and oil used. The dealer changed the oil and filter again when they did the oil pump. It's had two oil changes in 30 miles. No sign of water in the oil in the first change. I did notice oil in the exhaust on a cold start up. Had it warming up on the driveway about 10 mins, backed in on a hill and still managed three or four drops out of the exhaust. Discovered that about 2 hours ago.
You may have a tiny leak in the system since the pressure test show that. Have you changed the radiator yet?
@yaser
have not swapped the radiator but it does have plastic end caps so wouldn't surprise me. I sprayed everyone I could see but can't see them all without more of a tear down on the front end. I've used two different pumps/gauges on the test. Dropped from 15 lbs to 10 lbs in about 4 mins.
The leak could be internal.
Did you try another pressure tester to rule out a leaky tester?
Not sure how you feel about it, but you could try a bottle of Barr's stop leak.
@bc-st
My fear is internal, head gasket mainly. Since coolant and oil started acting up at the same time. I've used two pumps with different gauges as well as put them on my truck, the truck held both with no leaks. I'm pretty confident in the tester but it was about a 5lb loss in 4 mins. I want to hold off on barrs currently since the vehicle is under warranty to 125k miles. Dealer just cannot figure it out i guess, and they told me heater core lines were leaking, I could find no leak, replaced heater core lines plus the "t's" from the heater core to the engine anyways and no fix there. Carpet wasn't wet inside and no smell of coolant inside but it does have a rear heater core that I've only checked the lines from under the vehicle not the core itself
Is you oil lever over full? Is the oil milky? Have you checked the transmission fluid for coolant contamination?
Do you think the coolant is getting into the engine oil or cylinders? You could try pulling the spark plugs and pressurize the system, although if it's loosing pressure as fast as you claim, and monitor it closely to keep the pressure up, then either crank the engine over and see if coolant sprays out of a spark plug hole, or use a bore scope to look for coolant in a cylinder.
If you haven't done so already, you might want to perform a combustion leak test with the blue chemical. You never know.
Put some dye in the coolant and see if it shows up on the A/C drain.
Possible that lower intake manifold is leaking coolant and coolant is finding its way into the crankcase.