I bought a used '98 Bonneville SE automatic transmission a little over a year ago from a private party, it has about 89,000 miles on it right now (I probably put about 6,000 miles on it myself) and as far as I can tell runs great but there are some odd things I have run across. I also want to get some suggestions/opinions on improving performance as well so I just put it all in one post in this section.

For starters the vehicle is using green coolant, when I bought the car the guy said there was some cooling system work done, unfortunately I didn't ask him specifics but I thought I could assume he did a full changeover from Dex-crap to real antifreeze since the radiator coolant was green. Now I have absolutely no issues with high temp even after running the car at about 100 MPH for a few miles but the odd thing is I noticed the puke tank had an odd color to it, it looked like it was a little reddish/orangish. The radiator itself however is very much green. So I emptied the puke tank, rinsed it a bit, and placed antifreeze (green) in it. A few weeks later the puke tank again became an odd color. It'* the same fluid level and I have had no issues, no odd overheating.....nothing. Now obviously this isn't a good sign but I want to know exactly how bad is it? Is a full flush truly needed? Is it really bad if Dex-crap and green antifreeze mix even if it'* not a lot of Dex-crap? I have read that if they mix they become a gooy sludgish substance.

Which brings me to the next question. I've been lurking these boards for quite a bit (awesome site BTW) and have read a lot of terrible things about upper intake manifold failures. I know a couple of people with the same engines, except in Buicks, and they haven't had any issues with it. I'd rather spend the $$ and time doing other things on the car. Should I really be worried about it even though I have no overheating issues or missing coolant? Lets say I decide not to replace it and let it go until it fails, is there a good chance the engine will become unusable? Are there any early signs aside from losing coolant fluid or overheating?

My other issue is I have a loud whining pump, me and my friends are convinced it'* the power steering pump. My steering is fine and everything but the pump gets really loud when I start turning the wheel with the engine running. It'* really more of an annoyance than a problem however I plan on replacing it sometime soon. I have a Chilton manual, maybe it'* a Haynes I forget, and the manual seems to be worthless in regards to replacing the power steering pump. The damn pump is in a bad area and I honestly cannot think of a good way to pull it and replace it. If anyone has done this before please PM me or reply with suggestions.

Now on to the performance talk . I have no delusions on thinking this car will be a competitive racer, I wish I had an SSEi , nor do I want to spend tons of cash but I would like a quick, fun car to drive. So far I haven't done anything except put in a hi-flow air filter (K&N drop in filter) and I also got a transmission flush which actually greatly improved performance. My plan so far is to gut the airbox using a nice picture guide I found on this very website , get a PCM (I'm looking at the basic one from Intense), and get new tires so I don't kill myself with the new PCM , not to mention I need new tires anyway. For the most part I just want the PCM to remove the speed limiter but I have read that it can improve shift points and improve cooling by kicking on the fan quicker or something. When I was looking at the order form at Intense'* website I noticed my car has two different numbers next to it that are maybe ratios or something (2.86 and 3.05). Does that have to due with wheel size or something? I don't have a personal picture of my car but this picture has the exact same wheels as my car if that helps any:

Any suggestions are welcome, I would also like to hear from someone who may have got the same basic PCM from Intense and if so if any of the other options are worth it. Again I don't want to spend too much money, nothing over a few hundred dollars not considering the cost of tires which again I could also take some suggestions.

Thanks in advance

hi welcome to the club to know if you have 2.86 or 3.05 look in youre trunk on the opton tag is you see F83 that 3.05

as for performance start whit a 180 degees stat a good cold air intake one step colder plugs maybe also clean youre TB

as for maitenance the problem whit all series2 its the lower intake gasket. that you should check if the cooling work done by the guys if he did change them

Hey, welcome to the club! You seem to have a nice car, and I hope we can help you make it work out for you. Sorry to hear about your problems, and I'd be glad to help you out.


That'* a picture of my 99 SLE'* pulleys. The power steering pump is the one with the few holes in it.

To change the pump:
Take off the belts and put your finger in one of those holes. Rotate the pulley until you can feel a bolt. There should be two (one on top & one on bottom) that are towards the front of the engine and easily accessible from the top. I believe the bolts are even in length and have 13mm heads. Whatever the size of the bolt, you'll need to use a deep well socket. They're not reverse-threaded, so just take them out in the regular fashion. Remove the hose clamps, take off the hoses (perhaps do this before the bolts), and the pump should come right out.

To prolong the life of your pump as well as your patience with it, put in some Lucas Power Steering Stop Leak. It'* kind of expensive, but if you use a turkey baster to suck out and displace some of your power steering fluid with the Lucas stuff, you should have an easier time steering and at least reduce the noise.

I'm not going to comment on the PCM or performance mods, until we've talked about your coolant issues...

Any chance you could ask the guy you bought it from exactly what was done as far as coolant work? And when? And by whom? Backed up with receipts?

In the meantime, do the following for us:

Remove the plastic engine cover (the thing that says "3800 Series II") and look at the top of the black plastic upper intake manifold (UIM)...you should find three date stamps giving month, day, year the upper was manufactured. That should give a good clue as to if (and when) it'* been replaced.

Look very closely at the gaskets between the aluminum lower intake manifold (LIM--this is what the black plastic UIM is bolted to) and the cylinder heads; hopefully you can see whether these LIM gaskets are the original black plastic design or newer silverish-colored aluminum.

From your description of the coolant recovery bottle discoloring...It sounds very much like someone only replaced part of the original Dex Cool with green. And anyone who did that probably didn't really do much in the way of "cooling system work," quite frankly. I would advise a complete and thorough flush out...though that may be a small part of your own cooling system work

And yes, the UIM (or the plastic LIM gaskets) can fail suddenly without prior warning, and they can dump massive amounts of coolant into the cylinders, potentially causing hydrolock (and bent rods...total engine bottom end loss). IMO, the first thing any L36 owner should address is the UIM and LIM gasket issue, even if they have no symptoms.

Finally, post us a good focused picture of the RPO code sticker (it'* on the spare tire cover, with a bunch of three-letter/digit codes...make sure the VIN# matches!), so we voyeurs can know what gears (and suspension, etc.) you have.

EDIT: Oh, and one more thing...can you confirm that the strange whirring noise is NOT coming from the bottom end of the engine itself; I don't want to unnecessarily scare you, but L36'* that have had internal coolant leakage can wind up with coolant mixed into the oil...and that can destroy the main bearings if allowed to sit.

thanks radomirthegreat, I wasn't expecting it to be that easy and apparently i got the 3.05. Thanks for the help.


It may be difficult to get ahold of the previous owner but I think I could try by looking them up from the name that was on the title if the DMV can give that info away. Otherwise I may be screwed :( , I found the car through autotrader.com.

I looked at the top of the UIM and there were only TWO stamps and not three. There was an 04 and the other one was a 9, leading me to believe it was probably September of 2004.

The LIM gasket appears to be black.

I don't have a digital camera at the moment but I took the time to write down all of the stuff from the RPO sticker and the VIN# did match .

AAA AG1 AG2 AK5 AP9 AS7 AT6 AU0 A79 A90 C57
C68 C97 DA1 DG7 DH6 DK6 D55 FE1 FE9 F83 IH2
JM4 KG9 KP2 K05 L36 MX0 M15 NF2 NP5 NV8 NW9
ORN PF5 QNX R7L R7N R9D UB3 UK3 UP3 US7 UV5
UW6 VH9 VK3 VM4 V73 1SD 1SZ 50U 56I 562 6KJ
7KJ 8RW 9RW


And if it means anything (because honestly I never knew about the RPO sticker )below that there was:

BC/CC U 116B 562

probably useless info but might as well.


EDIT: I'm quite convinced it'* the power steering pump because the sound seems to directly relate to moving the steering wheel. I've given the car like 3 or 4 oil changes and I never had anything look odd about the oil. It'* made that noise ever since I got the car and I have put a good 6k miles on it myself. Now that I found out the steering pump is easy to replace I'll probably get around to doing that soon. If that doesn't remedy the noise I'll have to look into what you say.

It'* good that you followed the explanation. I thought I could have been unclear in some of the wording. Also, be sure that you properly refill the power steering fluid if/when you change the pump. The pumps are really good at taking out air bubbles, but that means you'll have an empty power steering fluid reservoir if you don't spend about 10 minutes under the hood with someone spinning the wheel. Have fun! My 94 SSEi engine bay is different, and I recently had to undo most of the pulleys on the side of the engine and take off the plate that holds them because of a crack. This is like walking compared to that marathon I did.

I've done a few power steering pumps in my day , I have a good idea on how to do it. It'* just that when I noticed it was at the bottom of the engine (the others I have done have always been easily accessible) and there wasn't any access under the car I thought it was going to be a pain in the *** to do. That'* why I asked about it.

Very good to know.

OK, sounds like the UIM was in fact replaced...if you look at radomir'* pic above, you can see a little white sticker on the UIM just below the PCV valve cap; this sticker will identify whether the new UIM is a GM Delphi (AC Delco) part...does yours have this sticker?

(If not, you could have an aftermarket replacement part, which could be a GOOD thing)

Sounds like you've got original design black plastic LIM gaskets. They could be original or replacements, but either way they aren't the aluminum new design gaskets, and are thus unfortunately prone to failure. I would advise replacing them.

I'd like to say thanks for the help guys.

There was no sticker on the UIM so it may not have been a GM product.

I replaced my power steering pump and it has gotten rid of the noise for the most part. The pump still whines a bit when turning but is half of the noise it was making before with the old pump and I think it may even steer a bit easier now, then again that may be wishful thinking. It does seem to be going away the more I drive though. The noise also doesn't seem to be coming from the bottom of the engine so I think I am OK there (thanks for the heads-up on that though agrazela).

The pump was a bitch to get off though. The high pressure hard line on the pump itself simply would not come off. So we decided we should just try to get the other end of the hose off, pull the pump out and probably have better access to the line to get it off....didn't happen. That end was on tight as hell too and was difficult to get access to. So we had to cut the bastard and use a socket to get that end out since it had perfect access with a deep well socket but like no access with a damn wrench with the hose still not cut . So about $95 later (~$20 for a new line since we had to cut it ) we slip in the new pump and line, that part took like minutes but taking the ****er off was like hours including smoke breaks. So what should have taken 2 people like an hour to do took many because some damn bolts were on too tight. And they were REALLY tight, the bolt was all twisted and stripped from wrenching on it by the time we gave up on it.

Next I'm gonna empty out my radiator and make sure there is no mixing of dex and antifreeze.

So nobody has any experience with PCMs on these cars? Are they worth it?