1998 Yukon low operating temperature

[olliec420]

Hey Guys, I have been reading here and I think I know what's going on now but looking for some clarification. So I got this thing from a guy who told me he had just put in a new radiator. The operating temperature is as shown in attached photo once warm. When I start it the temp creeps up to 210 mark and then drops to here and stays.

At first I thought, oh good, cooler is better. It occurred to be the other day (after seeing a post on another forum) that my intermittent catalyst codes may not be a bad cat but low operating temp?

Then in reading more here it looks like it could be a missing restrictor in the new radiator. When I had a 1997 Tahoe back in the day (2001, young, dumb and all that jazz) I had the radiator replaced and same low temp. And same intermittent cat codes.

Why TF don't after market radiators have the restrictor?!? I will try the hose clamp to test. Im understanding I want to partially clamp the small hose that goes to the semi-clear plastic tank on the passenger side? Is that correct? Does anyone have a photo of how that should look like? And what type of clamp, a round screw adjusted type or a plastic scissors type?

 

[Hoesgottaeat2]

The pic you posted is pretty typical range for normal operating temp. (2) of the (4) rigs I've owned of this generation do the same thing consistently without issue. The first few minutes of driving it'll climb to close to the 210 mark and once the thermostat opens it falls back to what appears to be around 155ish degrees range(as shown in your pic).

 

[strutaeng]

Yeah, it seems normal on a lot of these trucks. My 00 k3500 never goes past 1/4 mark.

But if I hook up a scanner, the ECU correctly reports like 185F in my case...

 

[olliec420]

Yeah, it seems normal on a lot of these trucks. My 00 k3500 never goes past 1/4 mark.

But if I hook up a scanner, the ECU correctly reports like 185F in my case...

I'll check with the scanner and update when Im home later.

 

[Eman85]

I'm in for using a scan tool to get a better temp reading. 26yo dash gauge might be a little inaccurate, they are more of an indicator than a gauge. I've replaced a lot of those radiators and used all different brands and didn't have any problems or modifications necessary.

 

[olliec420]

Hmmm, you're right. The scanner says temps are 194-199 while running.

Ok so why intermittent catalyst codes? Is it really bad or could there be anything else to look for. All four o2 sensors are new.

 

[strutaeng]

Hmmm, you're right. The scanner says temps are 194-199 while running.

Ok so why intermittent catalyst codes? Is it really bad or could there be anything else to look for. All four o2 sensors are new.

What code(s) are you getting?

Could be completely different thing going on. You replaced tbe O2s? Or the previous owner?

Maybe it's a legit issue with the catalytic converter and someone replaced the O2 sensors thinking (or hoping) that was the real problem?

 

[olliec420]

What code(s) are you getting?

Could be completely different thing going on. You replaced tbe O2s? Or the previous owner?

Maybe it's a legit issue with the catalytic converter and someone replaced the O2 sensors thinking (or hoping) that was the real problem?

I replaced all four sensors after I bought it when the code came up and because as far as I know the sensors are 20+ years old. Im not sure the exact code off top of my head. I will post it when it comes up again. I cleared it a couple days ago. Its like "catalyst performing below threshold bank 2."

 

[Eman85]

How old are the cat converters? These systems are old and react differently. I removed the cats on my 98 K2500 and the O2 sensors are there but it never sets a code.

 

[olliec420]

How old are the cat converters? These systems are old and react differently. I removed the cats on my 98 K2500 and the O2 sensors are there but it never sets a code.

As far as I know they are original.

 

[olliec420]

code...

 

[strutaeng]

code...

I'm pretty sure that means your catalytic converter is bad...

I think you can check the surface temperature of the inlet vs outlet. Someone please post what that needs to be; I've never had this issue before.

 

[east302]

Here is the diagnostic from the 98 manual. Do you have any exhaust leaks on the passenger exhaust?

If you have a scanner, graph the up and downstream O2 sensor voltages together. The upstream will oscillate (lean to rich) while the downstream should be relatively stable. If it mimics the upstream, that means the catalyst isn’t doing well.

You could try swapping the downstream sensor with the other bank to see if the code follows.