ptcfast2 Posted May 1, 2011 Report Share Posted May 1, 2011 (edited) My 3.1 98 Lumina decided to overheat today. It was rebuilt about 8 months ago and has been running like a champ since. Anyways, it seems to have sprung a coolant leak in the the rear somewhere, and I'm unable to pinpoint the leak without tearing town the engine or removing the tranny. Not in the mood to do that just to put a band-aid on the motor! So, this leaves me with an engine replacement. I'm leaning towards a new 2003 LG8 3100 crate engine but I'm questioning the differences between my L82 and the LG8. Has anyone attempted this/know the differences/parts I would need? Edited May 1, 2011 by ptcfast2 Quote Link to comment Share on other sites More sharing options...
AL Posted May 1, 2011 Report Share Posted May 1, 2011 It sounds like the heater core hose has a crack in it but the crack is so small that it will only leak under pressure... Fill it with coolant and leave it idle on jack stands until you can pinpoint the leak Quote Link to comment Share on other sites More sharing options...
ptcfast2 Posted May 1, 2011 Author Report Share Posted May 1, 2011 Leak is coming from the rear head somewhere...or the front seal. This engine has leaked in enough places over the years where I can't make heads or tails of anything. Sadly that means I can't pinpoint it without tearing down the engine or removing the transmission. Not in the mood to do that, I've put enough work into this engine to get it to 234,000 miles anyways. Quote Link to comment Share on other sites More sharing options...
Andrew Posted May 1, 2011 Report Share Posted May 1, 2011 if there is too much residue from past leaks, clean up the engine with simple green and a pressure wash. I think Al is on the right track with the leak, especially if the motor was rebuilt recently. Very likely the heater hoses werent replaced. The overheating could have been caused by a simple t-stat failure. Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted May 1, 2011 Report Share Posted May 1, 2011 pretty much the same exact thing. Only differences are internal. Quote Link to comment Share on other sites More sharing options...
ptcfast2 Posted May 1, 2011 Author Report Share Posted May 1, 2011 (edited) if there is too much residue from past leaks, clean up the engine with simple green and a pressure wash. I think Al is on the right track with the leak, especially if the motor was rebuilt recently. Very likely the heater hoses werent replaced.The overheating could have been caused by a simple t-stat failure. I replaced the stat and tightened the housing bolts in the parking lot of an Aldi when it broke down yesterday. I saw a dribble coming from the housing so I wanted to rule it out. The leak is coming from the rear passenger side/center of the engine by means of the oil pan, heater hoses aren't leaking either. The 3.1 has ALWAYS had a slow leak that required a top up of the coolant every few months since I bought it 2 years ago, but it seems that that slow leak became huge. This car has also had issues with overheating at idle that I could never fix: Replaced radiator, cooling fan motors, relays, hoses, flushed out all Dexcool, replaced LIM gaskets, bled it over and over again, etc... pretty much the same exact thing. Only differences are internal. Maybe I'm mistaken, but wouldn't the existing fuel rails/injectors need to be used from my current 3.1? I thought that was one of the major changes internally, besides improved intakes and heads. Edited May 2, 2011 by ptcfast2 Quote Link to comment Share on other sites More sharing options...
zipper Posted May 2, 2011 Report Share Posted May 2, 2011 I'd just drop in a 3400 in it. Pretty much the same thing but you might need to use your 3100 mounts depending on what the 3400 came out of. IIRC the LG8 was just a 3100 with 3400 UIM & LIM with maybe a couple other minor differences. Quote Link to comment Share on other sites More sharing options...
ptcfast2 Posted May 2, 2011 Author Report Share Posted May 2, 2011 I'd just drop in a 3400 in it. Pretty much the same thing but you might need to use your 3100 mounts depending on what the 3400 came out of. IIRC the LG8 was just a 3100 with 3400 UIM & LIM with maybe a couple other minor differences. The only reason I'm leaning towards the LG8 is because I can get a brand new one for about $1,800 and it seems like it would be a drop in and go affair. This car was my DD so I'm scrambling to get it back on the road as fast as possible. The 3400 seems like more work according to what I've read (the 3400 swap guide outlined what needed to be done, but it seemed to be geared towards 1st Gen W-Bodies more than the 1.5 Gens so I ended up a bit jaded after reading it). Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted May 2, 2011 Report Share Posted May 2, 2011 I did a L82 toLG8 swap a couple of years ago. Need to buy an egr adapter or block off plate from WOT tech. Quote Link to comment Share on other sites More sharing options...
ptcfast2 Posted May 2, 2011 Author Report Share Posted May 2, 2011 I did a L82 toLG8 swap a couple of years ago. Need to buy an egr adapter or block off plate from WOT tech. WOT-Tech mentioned that the 3.1 engine included with the 96-99 models has the same EGR connector as the 2000+ engine. So I'm pretty sure I won't need an adapter as I can use the EGR that comes with the new engine. I'm assuming you had a 94/95 model when you did the swap? Any other hiccups or was it smooth sailing? (Sorry for the questions, $1,800 is just a lot of money ) Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted May 2, 2011 Report Share Posted May 2, 2011 Oh yeah, sorry. When I did the swap, I had to use the factory 96 GP rear manifold with correct downpipe location. So I had to use the block off. You won't have that problem since you have a gen 1.5. Other little things: The alternator to UIM brace can't be used The fuel rail needs to switched (you might not have to) Swap the guts of the L82 throttle body into the LG8 throttle body. Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted May 2, 2011 Report Share Posted May 2, 2011 Here's what it looked like when I was done. Damn I miss that car Quote Link to comment Share on other sites More sharing options...
ptcfast2 Posted May 2, 2011 Author Report Share Posted May 2, 2011 Other little things: The alternator to UIM brace can't be used Do you mean I can't use the brace from the LG8 and I'll need to swap the one from the L82 in or do I need to buy an alternator that fits? Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted May 2, 2011 Report Share Posted May 2, 2011 Well, I used the alternator from my L82 and just went without the brace. You're situation may be different. Quote Link to comment Share on other sites More sharing options...
ptcfast2 Posted May 2, 2011 Author Report Share Posted May 2, 2011 Gotchya...I really appreciate your help. I guess I'll be ordering the motor tomorrow then! Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted May 2, 2011 Report Share Posted May 2, 2011 Good deal. You'll notice a big difference on the topend Quote Link to comment Share on other sites More sharing options...
ptcfast2 Posted May 8, 2011 Author Report Share Posted May 8, 2011 (edited) Quick update: Manage to get it installed today. Bolted right up to the existing transmission and everything is in working order. Took it for a quick drive once I got the cooling system bled. I thought bleeding it was bad on a regular motor...since this motor was brand new bleeding the system was quite the chore as I had to get A LOT of air out. No check engine light, etc... seems like I'm in the clear so far! In the event someone stumbles across this post wanting to do a swap like this on a 1997-1999 1.5 Gen Lumina/Monte Carlo heed the following: -The O2 sensor on the rear exhaust manifold is different. Use the sensor you already have. - Have some flexible hose handy and run it from where the existing EVAP line is --> the LG8's evap assembly on the upper intake. -EGR has the same electrical connector. It's a bit tricky to get the metal pimping to fit around the heater hoses, but it can be done with a bit of force. -You may need to reuse the pipe that comes out of the thermostat housing and goes to the lower heater hose. The one that comes with the engine may or may not fit. -You may need to shorten/cut your upper heater hose to fit the coolant pipe that connects to the throttle body. The one on the LG8 might be a bit longer. -The alternator mount & alternator from the L82 fits on the LG8. Simply take it off the L82 and mount it on the LG8. -All other engine mounts fit on the LG8 without much modification. You might need to remove a bolt or part here or there to get to the bolt necessary hole, but everything can be used. -Camshaft position sensor needs to be replaced with the one from the L82 as the connectors are different. -Coolant temp sensor needs to be replaced with the one from the L82 as the connectors are different. -You need to reuse your fuel rails, FPR, and injectors from the L82 (the engine runs fine with them). -Google "3400 swap guide" for information on the throttle body. You need to swap some components to make the "better" TB work - really easy - just follow the TB section within the guide. -The thermostat housing may or may not have a bleeder. Take the one from the L82's housing and screw it in the LG8's thermostat housing for an easier time bleeding the cooling system. -Use a 3/8 drive stubby wrench with a 18MM socket to get the rear-most transmission bolt out. Makes that tight space a piece of cake to work in. Edited May 8, 2011 by ptcfast2 Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted May 8, 2011 Report Share Posted May 8, 2011 Need pics and videos! Quote Link to comment Share on other sites More sharing options...
ptcfast2 Posted May 8, 2011 Author Report Share Posted May 8, 2011 Need pics and videos! Here's two I took this morning. Nothing special but I think it looks quite nice! Now I just need to clean my coolant overflow tank...would you believe it's actually only a year old?! Quote Link to comment Share on other sites More sharing options...
Jonpro03 Posted May 8, 2011 Report Share Posted May 8, 2011 Fantastic! Looks like a factory install! Quote Link to comment Share on other sites More sharing options...
Jssuper Posted May 8, 2011 Report Share Posted May 8, 2011 Clean install for sure. I really like the LG8 3100, mine has treated me very well all these years. Quote Link to comment Share on other sites More sharing options...
dohcnut Posted May 18, 2011 Report Share Posted May 18, 2011 Leak is coming from the rear head somewhere...or the front seal. This engine has leaked in enough places over the years where I can't make heads or tails of anything. Sadly that means I can't pinpoint it without tearing down the engine or removing the transmission. Not in the mood to do that, I've put enough work into this engine to get it to 234,000 miles anyways. if its not the heater hoses or steel pipes it's either the LIM wasn't torqued right or the head was pitted and they reused it anyway(common on these) or possible rtv contamination of moulded rubber sealing surfaces. the only other thing that leaks coolant there on these--and is often misdiagnosed as LIMG leak is FRONT TIMING COVER GASKET as the timing cover also doubles as a kind of water manifold, I have seen this quite a few times and heard horror stories of LIMG's being done three times and a head gasket job being done because of the still present TIMING COVER GASKET leak. I am a professional mechanic. Quote Link to comment Share on other sites More sharing options...
ptcfast2 Posted May 19, 2011 Author Report Share Posted May 19, 2011 if its not the heater hoses or steel pipes it's either the LIM wasn't torqued right or the head was pitted and they reused it anyway(common on these) or possible rtv contamination of moulded rubber sealing surfaces. the only other thing that leaks coolant there on these--and is often misdiagnosed as LIMG leak is FRONT TIMING COVER GASKET as the timing cover also doubles as a kind of water manifold, I have seen this quite a few times and heard horror stories of LIMG's being done three times and a head gasket job being done because of the still present TIMING COVER GASKET leak. I am a professional mechanic. Well it's all water under the bridge now. New engine installed, not worried about the old leak anymore really (although I'm still curious and I plan on taking the old engine apart to see what I can find). It might have been a timing cover gasket, but that gasket was replaced when I had the tranny rebuilt a few months ago and never leaked after that. This was a sudden HUGE leak not coming from a hose or freeze plug. Reached the ground via the oil pan. Quote Link to comment Share on other sites More sharing options...
ptcfast2 Posted May 19, 2011 Author Report Share Posted May 19, 2011 Alright, little problem that came up that I can't seem to figure out: A few times over the past couple of days I've had a "loss" of something...but I'm not sure what. To be specific, it happens when I brake hard - the headlights will dim and the blower motor will momentarily slow down for example. If I let off the brake everything goes back to normal. Mind you this only happens when I brake from a high speed - low speed does not seem to replicate the problem. I'm not entirely sure what it could be - either something vacuum related or possibly a loose electrical connection that jiggles around under hard deceleration? Quote Link to comment Share on other sites More sharing options...
Crazy K Posted May 20, 2011 Report Share Posted May 20, 2011 sounds like too much load on the power system... most likely stemming from a poor connection, such as a loose ground or alt connection? check the alt's heavy wire, and make sure you properly attached the grounding strap for the engine... Alternatively, You could just have a weak alternator... Quote Link to comment Share on other sites More sharing options...
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