Coolant pressure test 5.9 Mopar

[stoinkythepig]

I replaced the timing chain cover gasket on my 1999 Durango last Saturday. The coolant flows through the cover, and the gasket between the cover and the block had failed causing a slow leak.

I took it for a 20 mile test drive (mixed highway/town and lots of steep hill climbing at WOT) when I was done and it showed no signs of leaking or overheating. IT was pretty cold out though.

After an extended drive on one of the warmer days this week, it had a faint coolant odor. It was also about a pint low on coolant in the radiator and the overflow bottle was empty. I topped off both and I have been pressure testing it for 15 hours.

The pressure tester gauge indicates that it lost about 3 psi overnight but there are absolutely no signs of coolant leaking under the hood or in the cabin. The oil shows no signs of coolant in it. I disconnected the coil wire and turned the engine over, but there was no indication of hydro-lock so I'm reasonably sure there's no problem with an internal engine gasket or casting.

I'm utterly baffled by this one. The original leak was really obvious and it's clearly not leaking in that spot anymore. The only reasonable explanation I have is a three part: 1. I left a little coolant somewhere on under the hood during my repair and it finally got warm enough to evaporate causing the odor the other day. 2. There was an air pocket in the cooling system leftover from my repair work and that caused the low coolant levels. 3. The coolant pressure tester is not perfectly sealed and leaks a little air.

Any ideas?

[Fitz]

I'm not sure what your initial pressure was, but a drop of 3psi over 15 hours is a fairly low pressure decay rate. My guess ... and it is simply that based on not having seen your truck... is that you had some air in the system. It's common after putzing with the coolant system. If she continues to drop over time then look into it. Beyond that, just drive her.

Fitz

[Degsy]

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I agree. Probably an air pocket. When it purged the pocket, it overflowed for a second as the bubble hit the overflow tank and then sucked what it needed into the system, emptying the overflow tank again.

[mikeb]

just throw a gal bottle of 50/50 mix of antifreeze in the back just in case. i wouldn't sweat it.

[Hoon]

I agree with the posters above.

My car usually sucks up a little coolant for the first few heat cycles as the air works itself out, and then it's all set.

If it's still consuming coolant after a few cycles, than it's cause for concern. At this point, no worries.

[stoinkythepig]

Thanks for the replies. I will heed your advice.

[stoinkythepig]

Update:

I thoroughly rinsed under the hood yesterday and drove the Durango for three hours. It continued to have a coolant smell outside, when parked, and the coolant reservoir was down a bit this morning. I tested the brand-new (as of last week) radiator cap and it failed miserably. I gotta think that was the problem. New one is on there now.

[ginness72]

Not to be negative but, I had a 98 jeep gr cher with a 5.9 and around 96,000 i had a bad head gasket... the good part was it was using coolant instead of putting exhaust gas into the coolant.. I had lost my job and had no choice but to try a sealer/ poor into fix ( bars leak ) . To my surprise it worked for over 2 years. I followed the instruction to the tee.. then a little over 2 years later i ended up getting the killer... exhaust into the cooling system... My jeep 5.9 you had to run 91 octane all the time and it would still ping if i went WOT.. hopefully you have fixed yours just an Fyi. I loved my jeep , that thing had so much nut.

[stoinkythepig]

I'm pretty sure the head gaskets are fine. If they ever fail, I'll just replace them.