quakerj Posted May 24, 2020 Report Share Posted May 24, 2020 Howdy fellas, here's a brief history: purchased a '96 Grand Prix 2 years ago and just this spring I've gotten around to fixing it. When I bought it, it was clear it was having overheating issues and was neglected by previous owner. Cooling fan was hot wired to run all the time, thermostat was cut out leaving just the gasket, coolant in oil (though not terrible), and tons of stop-leak added to the coolant (evidenced by copper sludge in overflow tank.) I was 99% sure it had progressed from standard intake gasket to head gasket because I had coolant burping out of the radiator anytime the engine was running (even cold) and there was evidence of coolant overflowing from the overflow bottle. I ripped everything apart and replaced head gaskets and about everything else I came in contact with (within reason). Bought some rebuilt heads from Rockauto so I could eliminate head warping from the equation. Block seemed okay so I left it as is. I've got the car running now and it runs smooth, does fine on test drive and coolant stays around 190* when running on a scan gauge. No stored codes after a lengthy drive. What seems bizarre to me is that after idling for 5-10 minutes (from cold) the valve covers get scorching hot, hotter than the plenum, and when opened up I see a lot of what appears to be steam inside. Oil doesn't show any serious evidence of water getting in it but I've only had it running for a short time. It seem to be turning brown quickly though and I've changed it once already even after the initial fill. Put a cooling system pressure tester on it and it seems to be holding reasonably well, but it'll bleed off a few PSI after an hour or two. Could I possibly have an intake gasket leak and is there any surefire way to confirm this other than to keep driving it and monitor coolant levels / look for water in oil? Any way to check the head gasket sealing to be sure something isn't amiss there (like a cracked block or something ominous)? I have a hunch that something isn't right. Probably should have gone the used engine route (found a 90k mile cherry 3.1L at the junkyard the other day) and I can still do that.. But I want to confirm what the issue is with the one I have before I go through that amount of work. Open to suggestions on where to go from here and what I can do to narrow this down. I don't suppose it's normal for the valve covers to get that hot given they're insulated by a rubber gasket. Quote Link to comment Share on other sites More sharing options...
digitaloutsider Posted May 25, 2020 Report Share Posted May 25, 2020 Intake gasket leaks typically present themselves in obvious fashion, such coolant getting into the oil. I mean the engine IS all aluminum from the heads up, and aluminum is a pretty good conductor of heat. How hot is "scorching"? Do you have one of those cheap IR thermometers so you can get an actual reading? You shouldn't have steam coming out of the valve covers, but a small fine oil mist is possible. Quote Link to comment Share on other sites More sharing options...
quakerj Posted May 25, 2020 Author Report Share Posted May 25, 2020 After getting up near operating temp you can't touch the valve covers for more than a second--- they're substantially hotter than the upper intake/plenum. I see a good amount of "vapor" inside the valve cover with the engine running but there's no real pressure, so it could very well be oil mist and not steam that I'm seeing. Suppose it could be normal but I haven't had enough drive time to really see if there's something wrong. In an unfortunate turn of events I'll have to redo the lower intake gasket anyways. I was threading in a new coolant temp sensor (O'Reilly sold me a bum one which had the temp gauge pegged all the time, though it reported the temps to the ECU correctly) and the lower intake cracked at the threads. I already have the LIM pulled and I see no evidence of gasket failure or anything amiss. So I have to pick up a LIM at the junkyard and a gasket set & reassemble before I can test further. On the plus side I'm getting to know my way around this engine quite well. In the interim I've decided I'm going to pick up that 90k used engine I spotted at the pull-a-part the other day, probably the transmission too. I plan on keeping this car a long time, if the current engine turns out fine, I don't mind having a spare. But on the off chance I do need it, finding a low mileage 3.1L is next to impossible. Is it possible to pull the engine and transmission together out the top, and how difficult is this? It would be coming out of a 1996 Cutlass Supreme-- looks like an old granny car that got sideswiped which is why it's in the junkyard. Had nice crystal clean dexcool in it, oil color looked good, so it looks promising. If there's any helpful info you can give about pulling the engine/trans combo, I'd sure appreciate it. Quote Link to comment Share on other sites More sharing options...
mfewtrail Posted May 25, 2020 Report Share Posted May 25, 2020 If you're going to the actual yards named "pull-a-part" they have gantry cranes for pulling engines/trans and I would just drop the entire subframe assembly out the bottom, then separate the engine/trans from it. Search the board here and you should find some information about dropping the subframe. digitaloutsider 1 Quote Link to comment Share on other sites More sharing options...
55trucker Posted May 25, 2020 Report Share Posted May 25, 2020 (edited) L82 engines might be on the short side but LA1 engines are in abundance. Edited May 25, 2020 by 55trucker digitaloutsider 1 Quote Link to comment Share on other sites More sharing options...
digitaloutsider Posted May 25, 2020 Report Share Posted May 25, 2020 I was going to suggest the same. Could be a great time to upgrade to a 3400 and get some extra horses. Quote Link to comment Share on other sites More sharing options...
55trucker Posted May 25, 2020 Report Share Posted May 25, 2020 Yeah, that move to me is a no brainer..... Quote Link to comment Share on other sites More sharing options...
quakerj Posted May 26, 2020 Author Report Share Posted May 26, 2020 (edited) I'll look into the 3.4L swap more, last I checked on it I remember enough things needing modified that it seemed not be worth the extra headache for the 20-odd extra horsepower. I picked up a junkyard lower intake manifold and slapped it on, just waiting for RTV to set and still have to throw the power steering pump on and a few other odds and ends. Should be able to try it out tomorrow afternoon sometime. Keeping my fingers crossed that it runs good with no issues. The LIM that I found at the junkyard looks a bit different than mine. It has a huge "98" stamp in each corner and the thermostat housing to me seems a bit different. I bolted my old one to it and it seems like it's off center a bit, though I can tell it will still seal. Thought that was odd. Had a different casting number, but everything bolted up fine, so it should work just fine. Edited May 26, 2020 by quakerj Quote Link to comment Share on other sites More sharing options...
quakerj Posted May 27, 2020 Author Report Share Posted May 27, 2020 Update-- got the engine all back together and took it out for a good test drive. Pretty sure I'm looking at a cracked block or something beyond the standard lower intake gasket leak or head gasket. After a short drive I can see steam inside the valve cover and condensation on the oil fill cap. After driving just a few miles, the valve cover gets so hot you can't touch it, basically as hot as the radiator hoses, while the upper intake you can touch comfortably. I believe I've eliminated heads and head gasket as potential issue since they've been replaced. Compression checks out okay, about 175 PSI on all cylinders. I'm certain the LIM gasket is sealing, the one I just took off (to replace LIM that I cracked while installing coolant temp sensor) showed no signs of leaking, and when I put it back together I used a brand new Felpro LIM gasket set, the steel one. Something definitely seems amiss. I will read up on the 3.4L swap as I will probably go that route-- I'll be darned if I let this car get the better of me, but it's definitely trying! On a side note, does anyone know what temp the cooling fans should kick on? Engine stays rock solid at 185F while driving, but idling in my driveway after a drive it creeped up to about 205F before I shut it down and the cooling fans never came on. I tested the relays and they're okay. Thanks all for your help, it's greatly appreciated. Quote Link to comment Share on other sites More sharing options...
55trucker Posted May 27, 2020 Report Share Posted May 27, 2020 The plenum under *normal* conditions will be cooler than the covers, the plenum is *dry* meaning that no coolant flows thru it. It is also above the manifold, air can pass beneath it, when the vehicle is moving it will generally be cooler than the engine, the only time when this will differ is when the vehicle is stationary, the engine is idling for something more than a short period of time. The primary fan engages at approx 213, the secondary at approx 230. Quote Link to comment Share on other sites More sharing options...
quakerj Posted May 27, 2020 Author Report Share Posted May 27, 2020 Thanks for that info, I suppose it does make sense for the plenum to be cooler since air is passing through it constantly. I'll keep driving it and I'll know soon enough whether coolant is getting into the crankcase. While the oil does look quite dark for the short time I've been running it since changing the oil, there's no noticeable water/coolant contamination that I can see (other than condensation collecting on the oil cap). I hope I'm just being paranoid! Will report back after more drive time. Quote Link to comment Share on other sites More sharing options...
quakerj Posted May 28, 2020 Author Report Share Posted May 28, 2020 Went for a 30 mile drive today, no drama. After I got back I left the car idling for 5-10 minutes while I checked the transmission fluid. I also wanted to make sure the fans would kick on once the engine got hot. Temps climbed to 225, read from the OBD-2 port with my scan gauge. The analog gauge on the cluster is a little off, it read about 210 when the ECU was reporting 225. Not a peep from the cooling fans, not sure why they're not turning on. I rechecked the relays and the contacts close and I measure no resistance when 12V is applied to the coil. I used a jumper wire at that fuse block on the two wires that the fan relay would normally close and each fan kicked on just like it should. I'm at a loss why the fans aren't switching on, and a bit uncomfortable letting it run past 225F waiting for them. Any ideas on this? Quote Link to comment Share on other sites More sharing options...
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