Question after upper and lowergasket rplmnt

daughters 1998 La sabre hesitation then hydro lock at idle then died. doin the dad thing did research on this great site and found out about the gasket issue. Got felpro gaskets upp\lower kits. No dex cool in oil and upon removal of the L\I found cyl. 5 intake full of dex cool
. Vacuumed all coolant and debris out, cleaned all surfaces and commenced gasket replacement. All back together and removed spark plugs and injector connector and cranked her over, alot of coolant came out, let it sit 2 days cranked it over a few times and dry.installed plugs and Inj. conn. and the engine started hesitated\white sweet exhaust smell and died. Checked oil and now there is green coolant in the oil,green is what i replaced the dex cool crap with. The hydro lock did not appear to due any damage from idle,correct me if im misled.Question now is why is there now coolant in the oil? Could their have been a head gasket issue as well? My daughter said the temp gauge went up to the red once but most of you out there know how reliable the info from a 19Yr old is these days. Thanks in advance for any thoughts, Ron.

It is possible that the head gaskets failed, and possible that the heads warped as a result. It is also possible the replacement gaskets did not seal properly.

Was there any pitting or the lower intake flanges or the intake flanges on the heads?

all surfaces were very clean as far as corrosion goes, car has 180000 mi on the engine.

180K on a Buick 231 V-6 is at the "barely broken in" stage. With proper maintenance it is easily a 300,000 mile engine.

I would suspect that something did not assemble or seal correctly.

Weren't these engines subject to the egr passage in the upper intake cracking and allowing to coolant to crossover from the adjacent passage and wind up in the cylinders, Dorman makes an updated upper intake to correct this.

BigMopar is correct - That is a weakness in the plastic intakes, and I believe your upper is plastic (IIRC change-over was about 1995).

Good catch, Max!

thanks guys for the replies. I did not replace the upper plenum, and come to think of it the metal EGR tube and line to EGR valve had coolant in it when i pulled the plenum off. ill replace plenum and report back. Also believe the 300k mark as when i took the lower off i was amazed at how clean it looked, she bought from an old man who had regular dealer oil changes every 1500 miles. Had 160K when she bought.

I had a '95 LeSabre that was pushing 300K and still running fine, started every winter day, drove well, used no oil, but 20+ years of midwest salt spray finally started taking its toll on the body. The outer body looked good, but the trunk floor and cowl/kick area was getting weak, and it was time to go last fall.

I know you guys across the Lake get the same kind of treatment, but keep it clean and you may make it to that point or beyond - But don't fret over the durability of the engine.

A car hydro locks, when a cylinder fills with fluid(fuel, coolant)......

More often than not, this is caused by the upper plenum failure.......where the egr tube in the lower intake passes through the upper plenum, look inside the hole and you will probably see degradation of the plastic......coolant flows in the plastic around that hole......a pinhole will cause coolant to leak, fill up the cavities of the lower intake, and then run over into the intake openings to the cylinders....

Tech II, man you hit the nail square on the head. When i took the plenum off, the EGR tube hole on the plenum had a small 16d size eroded hole in it.Waiting on part.The members on this forum really need to be thanked for their knowledge on such issues,I know i really am greatful for the info and I will report back when i get new part installed, Thanks again guys.

I bought the Dorman plenum kit, which came with more then i expected, gasket, PCV valve assy. and lower IM EGR tubes 2 diff. sizes. My LIM already had the metal EGR tube which was around 3/4 in dia. the new replacement came in 3/4 dia the first 1/4" then narrows down to the dia. of a large straw, Its a good idea ,that way the tube has no way of touching the sides of the plenum. I replaced all parts and when i started the car and it seems to run good besides the nasty burnt smelling white exhaust coming out of the tail pipe. I didnt leave it run but a couple of minutes,Coolant resovoir didnt move but I dont think it got up to temp at the tstat, I did notice steam fumes coming from exhaust flange at exh. manifold. Any thoughts? I am thinking head gaskets? I am in no hurry for this car, the thing i shy away from is the exhaust man. bolts. That dam Midwest road salt!!

I have seen cars with so much coolant in the exhaust, they wouldn't even start.......I had to lift the front of the car to get the coolant to drain out before it would start........car smoked like crazy as the residual coolant boiled out.....

You have to do some serious overheating to get the head gaskets to fail on these engines...

I can almost guarantee you will have an air pocket in the engine once that thermostat opens......

You may need to get the exhaust system at full operating temperature and flow some serious air through it in order to expel all the glycol. Hopefully it doesn't contaminate the catalyst or O2 sensors.

I'll agree that the heads and blocks on the 231s are pretty robust, and they will survive overheating pretty well without damage. That engine had been made since 1963, was fully mature, and almost bullet-proof until the plastic intakes and coolant pipes appeared. A head gasket would be among the last items on the checklist.

That said, if there is coolant in the engine oil, drain it NOW before the coolant damages the bearing shells.

A car hydro locks, when a cylinder fills with fluid(fuel, coolant)......

More often than not, this is caused by the upper plenum failure.......where the egr tube in the lower intake passes through the upper plenum, look inside the hole and you will probably see degradation of the plastic......coolant flows in the plastic around that hole......a pinhole will cause coolant to leak, fill up the cavities of the lower intake, and then run over into the intake openings to the cylinders....

Is this referring to the hole in the bottom of the plenum just behind the throttle body?

What is hydro lock and how would I know the engine had it?