Had coolant in the oil; need advice for startup after repair

Not open for further replies.
Mar 19, 2005
I bought a 1997 Pontiac Bonneville for next to nothing. It had a failed upper intake manifold like they all eventually do. This led to coolant in the oil (it looked like the coolant was mostly water - not much "coolant" at all), failed headgaskets, and one slightly cracked head. I've just about got it back together properly, but I know that a few instances of lower end problems have occured after this repair. I actually already have a '98 Bonneville, for which I did the UIM repair. It didn't cause any lower end problems on that one, although it did get a little coolant in there at the end. I just did an oil change, and went on about my way. I don't know how long the 1997 went in this state, and I realize I'm rolling the dice. Is there anything additional I can do with the oil (specific oil, additives) that can help me put the odds in my favor?
Well if it were mine I would have left the drain plug out while doing repair, change filter and do a couple short of short oci's then a UOA to make sure you have no other problems.
Yep, the drain plug has been out for over a week. I've got a Wix filter and some throw-down Exxon 10-30 for startup. Should I run it for a few minutes, a few hours, or a few weeks before changing it again?
I'd run it around the block or something a few times get it up to temp and drain (might want to get a cheapo filter for the first couple changes)
Then a 1000 or 1500 mile change oughta do it.
Yea, an oil change pretty quick then a longer one like suggested above. Then do an oil analysis in 2 or 3 K more miles.
Could there be any advantage/disadvantage to using a heavier or lighter oil than one would normally run, at least initially? I'm trying to think this through, but that usually gets me in more trouble.
Use weight you'd normally use. After initial startup and up to operating temp. a look at oil (clean, milky?) will give you a lot better idea as to when to drain and refill than any suggestions you'll get here. If it still looks rasonably good I'd still change in couple hundred miles.

You will also want to be watching for coolant usage.
That said.....it is very likely that there will be some coolant level drop in the overflow bottle as the last bits of air are purged out of the system through normal usage over the first several days.

Get an oil anaylysis kit from Blackstone labs (site sponsor) and have an analysis done at each of the next few oil change intervals. That is after the "flush" changes that you will do.

Coolant in the oil can be doing a lot of damage before you will be able to tell by looking at the oil.

Looking at the oil, as advised, is still something you want to do. But you will still need to take it one step farther and get the anaylisis done.
It will only cost $20 plus the postage to send it in.

You don't need to use heavier oil just because the motor was exposed to water. Remember, water doesn't thin oil, only fuel does. The recommended oil for that motor is 10W-30. One other thing, that 3800 is a rock solid motor; so enjoy it.

BTW, I use the AC Delco PF47 filter in mine and get 67psi on cold start up.
Not open for further replies.