[KB$]

So here is the deal:

Purchased my 96' Deville from the original owner with 35,000 in the clock three years back. Since then I have put 4,000 more miles on it. For two years I drove daily for a 2 mile commute. After that stored it for 9 or 10 months. Recently brought her back out, changed oil, filter and fresh fuel. Immediately the AC compressor clutch went and took her off the road. I had a local shop change the compressor, recharge and AC is working well again. I am now however having some overheating issues. On top of that it is running rich but has the whole time I have owned it. When I bought it was hesitant to start so I had the FPR changed which fixed the start but then I started getting terrible gas mileage. I never addressed as but less than 1000 miles on a year.

Symptoms:
Overheated in traffic the other day it was about 85 degrees out. Temp reached 220 and it gave me a check engine light and coolant hot idle engine message. As soon as I got moving again it cooled right down.

Since then it has given me the same code 2 other times under seemingly random conditions.
I performed the highway test of 30-70mph back to 30 up to 70. Stayed cool on the highway then on the off ramp at the light have me the coolant hot idle engine code even though the coolant temp was 202. Every once and while I will get a backfire at cold start but not consistent.
Does seem to be running a bit rougher than usual.

Last night when pulling off a short highway trip it gave me the coolant hot code and then a change engine oil code

At idle the temp seems to fluctuate from 208-222.

Things I have checked:
-Purge line is clear, it is shooting plenty of coolant when running
-No residue under oil cap
-Coolant is not cloudy (it does however have pink coolant in it) I had a it flushed at a shop a few years back and it doesn't look like dex cool
-I can't seem to see a coolant fill line in the surge tank but I am not getting a fluid low code
-coolant doesn't smell like exhaust
-Not getting noticeable steam or condensation from exhaust
-Purchased a block test and tested from purge tank after running for 15 min and engine running - test fluid is dead blue
-Oil level- after I had the ac compressor changes the oil level on dipstick was low I assume bc they took the oil filter off to get at the ac compressor. I added oil and now is near max line after running.
-Water pump pulley seems to running fine from visual inspection, nothing obvious with tensioner
-Pulled the codes and attached a photo

What do I do next? Thermostat? Coolant Flush? Get the radiator tested?

Any help appreciated.

 

[Team ZR-1]

Since your getting a B2/S1 O2 (right side, before CAT) DTC and rich issues I would look at replacing at least the 2 front ones as a pair ASAP

Have you confirmed that the coolant fan(s) are working correctly ?

Use OBD-II scanner and monitor the PCM fans control as when it commands fans on and off and also monitor the coolant temp to see if temps match when fan is commanded on and off or if some fan relay or wiring issue.

Possible Tstat is sticking on random basis ?
Or the coolant temp sensor in block faulty ?

 

[Submariner409]

220 is nowhere near "overheating". The cooling fans do not even go to SLOW until 224 degrees. Fans go to FAST at 236 and overheat occurs at over about 265. The Northstar then goes into Camel Mode and will continue to run for over 50 miles without damage.

Correct oil level is at the middle 3 XXX mark on the dipstick. At or near the top is .5 quart overfilled.

 

[KB$]

Thanks guys,

@Team ZR-1 you are referring to the O2 sensors? How hard of job is that?

-When I turn the AC on both fans come on and seem to be moving air. Is there a better way to test?

-I'm not sure I can monitor the fan control commands on my scanner I may need to get a better one. The temp on scanner matches the dash.

I was thinking maybe just replace that tstat to see as it doesn't look that expensive.

@Submariner409 Agreed that what I can't figure it is going into fault mode but not reading over 220 on the dash. Should I worry about the overfill? Just drain .5 a court from the plug?


Does anyone know how definative the block test is for blown HG?

 

[Team ZR-1]

Yes the O2 sensors, best is replacing both front ones

You can get them at good prices on Amazon or local
Do NOT buy generic type, OEM best like Bosch

You need a O2 tool, cheap like $10 plus like these

O2 Tools

A OBD-II scanner that supports GM parameters (PIDs) would be easy to scan/record like

RPMs
Fan relays
MPH
Then you can match this up and assure fan comes on when the PCM is commanding the fan relays

Like this

In replacing O2 sensors

Look closely at the wiring to be sure no issues with them

1. First Unplug the O2 wiring connector from the wire loom and look to see that the connector on wire loom and pins look good
2. Use O2 tool and take old ones out
3. New O2 should already have anti-seize on threads
4. Install new ones with tool
5. Do not over torque them
6. Last plug O2 wiring connectors into wire loom - last

 

[Submariner409]

If you remove the thermostat make sure to replace it correctly and with the correct one for that engine. It begins opening at 188 and is fully open at 206 - the design engine operating temp range. If you try to hedge your bets and install a 160 degree 'stat it causes all sorts of problems because 160 degrees is right at emissions loop change coolant temp and causes all sorts of emissions troubles.

Thermostats are easy to check with a saucepan of water and a candy thermometer - begin heating the water and watch the beginning and fully open temps.

The cylinder block exhaust gas test, done correctly, is 100% accurate. You get exhaust hydrocarbons in the coolant surge tank, you have failing head gaskets due to pulled cylinder block head bolt hole threads. It's then disassembly and stud or insert time,

www.huhnsolutions.com

www.northstarperformance.com