'98 STS: (Buckle in...it's a long one )

It keeps overheating! Nobody can seem to tell me whats wrong & I'm exasperated! I bought the car in April. Had the dealership put in a new water pump (because it was leaking), and do a 100k mile service (even though it only had 94k on it) before I took it home. I did get a message on the dash about a month after I bought it that said "Engine hot - AC off" when I had the AC on. I turned the AC off & the temp went back down...no problem. Other than that, it worked great for about 2 months...then all of a sudden it started overheating. (Now may be the time to add that whenever the AC is turned on, it gets really hot, really fast. Is that normal???)
So I was driving home one Saturday afternoon (it was around 40 degrees outside). I wasn't paying attention to the temp - because at that point, why would I even think I needed to? It starts dinging out of nowhere & I look at the dash & it says "Engine Hot - AC Off" again & follows that up with "Idle Engine". I didn't have the AC on...it was way too cold for AC! So I look at the temp gauge & its directly over the beginning of the red line (topping out). Yikes!!! I pulled over as soon as possible but it still took me about 30 seconds or so, & by that time the dash was showing "Engine Overheated" and "Engine Coolant Hot". I turned the car off immediately & sat for a couple of minutes, then turned the key to acc to check on the temp. I had no idea what was going on or what to do. I get the same message about the engine coolant being hot, and now a message that says "Change Engine Oil", and the service engine soon light was lit up. To shorten this part up a bit - I was trying to run my heater & cool the car down (without turning on the engine) & I ran the battery dead. I ended up having it towed to my dads motorcycle shop just to have somewhere to store it for the time being.
(Oh! I forgot! My brother rigged the t-stat to stay open at all times after the first incident a month after I bought it, just to find out if it was the t-stat having issues opening. It wasnt.)
So after my Saturday afternoon overheating debacle, it's been sitting for about 2 months now. I've been afraid to drive it. I start it once a week and let it idle for 10 mins or so & it never gets past the halfway mark on the temp gauge. I decided this week to buy a new coolant tank cap & take the car for a spin. Mistake! I drove it about 4 miles, but no faster than 40 MPH. I pulled over & let it idle for another 10 minutes. All seemed well. I turned on the AC to see what happened. It got hotter within 2 minutes the temp gauge needle had gone up to the next line (the line after the halfway mark). I turned the car off completely & sat there. I took the new cap off the coolant tank & checked the coolant tank level. It didnt seem low...it actually started to overflow a bit, so I put the cap back on quickly. After about 10 minutes, I decided to drive it back home. I got to within 1/8 of a mile from my house (I live on a pretty steep, mildly long hill) & it started getting hot FAST. I could see 'steam' coming from under the hood right in the area where the coolant tank is located & I thought it was probably just the overflow burning off. I hate to admit this, but since I was SO close to home, I gunned the engine & shot up the hill in order to get it home rather than leaving it on the side of the road to get molested.
As soon as I stopped moving & 'parked' it, the dash read "Engine Hot - AC Off" and "Engine Coolant Hot" (again, no AC was on). I turned it off & popped the hood. WOW! The new coolant tank cap had blown off & fluid had blown out like a geyser!!!! It was everywhere, dripping from the hood liner & everything. I left the car alone for roughly 2 1/2 hours, then went & put about a gallon & a half of water in the coolant tank. Now there she sits...once again. Did the guy at O'Reillys give me the wrong cap? I've never heard of a coolant tank cap blowing off before.
I'm aggravated over my bad luck with cars (I just bought this car because my 2002 Jetta timing chain slipped & I had to have the entire engine rebuilt after only have THAT car for 10 months & I wanted to get rid of it before it happened again)!
Can anyone please help me???

I ran the OBD codes last night & there were so many I couldnt keep up so after they ran, I turned the ignition off & back on to run them again to get the ones I missed. The 2nd run only had about 1/4 of the codes on the first run! It seemed to erase a TON of the codes all by itself (I'm CERTAIN I didn't clear them). How is this possible??? Anyway, these were the codes I got written down on the first run (which all showed on the 2nd run also):

Current: B1009, C1761.
History: C1255, U1064, B1983, B1652, B1760, B1780, B1147, B1148, B1163, B1327, C1761.

Holy crap y'all...what am I up against here?
And also, thank you for your patience in reading this, and in advance for any help you can provide. I will be sincerely appreciative!

 

Oh, if anyone knows of any Cadillac SPECIALISTS in the Seattle metro area, please provide me with the contact info! Thanks!!!!

 

It would help if you posted code definitions.

 

Right, it probably would. I dont know what they are though. The OBD doesnt tell you what they mean, just list the numbers.

 

Description of codes and lotsa other good info here.

 

U1064 - Loss of Communications with DIM
This might be making all other code appear

 

Kinda gave up on the codes, but thanks for the link. I just wanted to update this post.

I took it to a couple shops & they both said it was NOT a blown head gasket.

I put a new thermostat in it, flushed the cooling system, filled it back up with a 50/50 mix of DEXcool & water and put a new OEM revervoire cap on it.

I can drive it on the freeway no problems. Wont get past the halfway (temp gauge) mark. Around the city, stop & go at lights, it's good. If I take it uphill, it starts to overheat though. The good news? It's not leaking a bit of coolant now, whereas before, it was bleeding the stuff. I think they gave me the wrong cap! (Hence the purchase of the OEM cap).

Anyway, I thought I'd update in case anyone cared to know what (mostly) worked.

I'm still going to try and figure out why it gets hot uphill...it will probably take me a while, but I will update as I get results

 

Are the electric cooling fans working properly, if they are not coming on when needed the coolant in the rad will not disapate heat as well. Once a Northstar starts to heat up it goes fast to the point of no return. Climbing a hill puts a load on the engine so that is not all that uncommon to overheat on a hill climb if something is wrong in the cooling system.

You say you have a new water pump and no coolant leaks so the fans and rad are the only other components to look at. Also is the water pump actually working, it has a drive belt that turns it which you can see under the small black metal cover on the drivers end of the engine.

 

Just wanting to update in case anyone is experiencing similar.
FINALLY found out that there was a small hairline crack in the head gasket. Mind blown. You would think ONE of the shops I took it to would realize that. My brother (my hero) finally guessed it right. I boughtt some thermagasket & my brother followed the directions & "fixed" my baby! I have had NO problem overheating AT ALL since. It doesn't get past the halfway mark on the gauge. My AC works great, my heater works great. I know it wont last forever, but until I can save up for a more permanent fix, that's what I've got.
Now I'm having an electric issue. HA HA!! If it aint one thing..............
None of the windows will roll. Up or down. The auto setting for the steering tilt & seat setting don't work (but they both work manually, just not the windows!) Nothing else on the panel is malfunctioning...just the windows. I had my brother test all the fuses (front & rear fuse boxes) and there are no fuses out. This is crazy. I guess my next step is to have him check the circuit breaker & HOPE that it is NOT a wiring problem (although, I would think it would have manifested before now if it were...)
So......................hope this helps anyone out who stumbles across it looking for help. (the tests they do at auto shops cant detect the tiny hairline cracks in head gaskets! Who knew?!)
Thanks for all feedback everyone!

 

FIRST TIME USER,,,,not sure if this is the right way to ask a question or not but here it goes,,,havn a overheating problem but going to put a new stat on and new hoses ,,took off the top plastic cover over the radiator and noticed the upper left side of the radiator there is a whole the which looks like a cap is supposed to be on it but cant find it ,,,was wondering if there is suposed to be a cap on that inlet or not?????? i can see right inside the radiator looks like there is supposed o be one but not sure,,,please help,,,thanks Bill,,,,480-652-7099 just incase someone can tell me,,,,