[smackentarfer]

Hello all! In November if 2021 I picked up a very well maintained 88 S-15 with a 2.5 and 171,xxx miles on it. The temps here in PA were already in the 30's and 40's, and my coolant temp never surpassed 160°F. As it started to warm up, my coolant temps would read up to 190°F. Now the outdoor air temps are well into the 90's during the day. This past weekend while on the highway, my temp guage was reading 210°F. It made me slightly uneasy because I had never seen it that high before. The only issue that this motor has given me has been high idling but it doesn't do it all the time. These temps are all based on an aftermarket Bosch temp guage that was previously installed. I came home and replaced the 185°F thermostat with a 160°F. The coolant temps are still climbing to higher than 190°F. I know that the temp guage may not be accurate, but what do normal coolant temps look like for these motors? I read that how these motors perform is based off of temperature. Any insight would be helpful!

 

[bk2life]

first thing, install a secondary temp gauge to verify if the one you're watching is correct. no need to go chasing ghosts

 

[Brawndo]

Based on miles alone it may be time to replace the fan clutch if it has never been done.

 

[2.2s101995]

Based on miles along it may be time to replace the fan clutch if it has never been done.

The faulty fan clutch on my 95 ended up in my spending weeks (and over $500) putting a new head on after it overheated. You can get a new fan clutch for $30 on rockauto, wouldn't be a bad idea to do. But 210 is not going to damage your engine. If it starts getting above that you have an issue.

 

[cerial]

1991 2.5 5 speed 2wd, standard cab short box, no ac, no ps. Truck has less then 145k engine has less then 40k.

195F thermostat, factory fan, factory replacment radiatior, factory hoses, factory replacment fan clutch. All through rock. Nothing upgraded engine is stock just preventive maintance.

50/50 mix. I live in Michigan.

I run between 190 to 210 and it gets up to 190 within 5 minutes of driving summer or winter. Standing still or going 90mph I have no overheating issues.

I noticed I was running 120 a while back and thought it may have been the sending unit. But the air out the heater was not as hot as normal in the morning. It turned out my thermostat was stuck open. Threw a new one in and it went back to normal.

 

[smackentarfer]

Thanks everyone for the responses. I will look into the fan clutch!

 

[S15E83]

Don’t discount radiator blockage, as well. What’s the inside of the radiator look like?


Sent from my iPhone using Tapatalk

 

[bk2life]

Thanks everyon

this is so easy to diagnos. Drive your truck to work. park, open hood and put your hand (ENGINE OFF) in between the fan blade and physuicllay touch the radiaotor. Move your hand all ov erht eentire radiitaotr. It should all be 200 degress.. so be careful dont burn yourself, but check the entire thing is hot. Many times when it gets internal blockage hald the radiator will be cold, and half will be hot.
So the rad not fully getting hot doesnt engage the fan clutch to cool the engine.
So before spend money, at least know what you are going to need.

 

[crazy_ate]

My 4.3 never gets above 170-175F even in 100F weather sitting in traffic
Ongoing issue, see below, Xrayscan tool showing consistent 192F at the ECM in 80F ambient easy driving 25 mph....turn out my dash gauge is NG

 

[Rhotpursuit]

My 4.3 never gets above 160F even in 100F weather sitting in traffic

Well...in that case, your gauge is inaccurate, or you have the wrong thermostat in it.

 

[smackentarfer]

1991 2.5 5 speed 2wd, standard cab short box, no ac, no ps. Truck has less then 145k engine has less then 40k.

195F thermostat, factory fan, factory replacment radiatior, factory hoses, factory replacment fan clutch. All through rock. Nothing upgraded engine is stock just preventive maintance.

50/50 mix. I live in Michigan.

I run between 190 to 210 and it gets up to 190 within 5 minutes of driving summer or winter. Standing still or going 90mph I have no overheating issues.

I noticed I was running 120 a while back and thought it may have been the sending unit. But the air out the heater was not as hot as normal in the morning. It turned out my thermostat was stuck open. Threw a new one in and it went back to normal.

My truck sounds almost identical to yours. No power steering, power brakes or AC. The radiator was replaced 40,000 mi ago and yesterday after driving home from work I felt all over the radiator and it was all hot. What temp does your fan kick on at? I haven't had any trouble with it getting up over 210 lately because the air temp isn't in the 90s anymore.

 

[cerial]

Clutch fan (thermal)
Ac delco 154360 off rock auto.

 

[crazy_ate]

Well...in that case, your gauge is inaccurate, or you have the wrong thermostat in it.

Interesting, after low speed drive...gauge ~170-175 using infra red temp gun showed top hose at 178F and lower hose at 143F on 85F day...cooling working just fine...cylinder head near plug 193F. Updated my 160F above to 170-175F...read the gauge wrong (operator error...beep beep boop).

 

[crazy_ate]

Well...in that case, your gauge is inaccurate, or you have the wrong thermostat in it.

Looks like I may owe you a beer....TBD

Your comment plus something in the back of my brain (been wondering about the low temp for awhile now) so I went down the rabbit hole.

So far, at a minimum, I think I have confirmed the gauge to be an issue (if the gauge is bad, I'm not going to replace the cluster as I have no interest in tearing into the dash -- famous last words), but I need to continue on my quest to confirm other items (thermo, sending unit, ECM, fan clutch, coolant ratio, etc)
This whole thing kicked off when I swapped out my OEM original thermo for a MotoRad failsafe 195F back in 2016. I don't think it's in "failed open" because ever since that install the thing never went above 170-175 on the guage -- but this truck gets very light use, mostly 25mph on residential roads.

According to my notes back in 2016, the stock thermo was running right at about 195F most of the time but would get to 210F on occassion. That seems to be right on point so I think my logic at the time was a 22 year old thermo (truck is '94 4.3L TBI) is evetually going fail so why not relpace it before it fails -- I do this quite often on things like master cylinders, starters, alternators, etc. If something has 70,000-100,000 miles on it -- even tough it hasn't failed -- I have no problem R/R and then keep the old one on the shelf as an emergency spare.

Anyway---- I'll let you know what else I find and how this story wraps up once I've figured it all out. Thanks again....I think .

 

[Rhotpursuit]

Check temps with a scan gauge.

 

[crazy_ate]

Check temps with a scan gauge.

Did some playing with my Xray Scantool in live data mode today...ECM is showing 192F (80F ambient temp, 77% rel hum, light residential driving=25mph), confirmed dash gauge=NG. Also used the infrared temp gun and confirmed engine temp on the block @ 188-193 (various test spots)...so ECM and sensor would appear to be both = OK. Just going to live with the defective gauge. Thanks again for the "motivation."

 

[smackentarfer]

Clutch fan (thermal)
Ac delco 154360 off rock auto.

Found out today that I have a mechanical fan. Maybe my truck just can't handle super hot weather!

 

[manbearpig]

There's something wrong with it then.

 

[cerial]

I replaced my water pump, radiator, radiator cap, fan clutch, thermostat, upper and lower radiator hose everything but the heater core and overfill as those are still good. Less then $300 including shipping for everything off rock auto.
I flushed the intake and the block separate. I got a 35000 mile engine that had been sitting. Flushed it and the heater core. Took me 6 times to get clear water. See pictures below

Also reverse flushed the heater core. You use low pressure and just let it fill one raised hose and drain out the other. The engine block and the heater core you absolutely need to use low pressure. The 4 cylinder intake ONCE REMOVED and stripped down can be used with higher pressure to clean the intake and clean out the inner passages.

But with a 2.5 the below method works. I just took several trips into the house filling 2 liters and letting them into the funnel and hose. It just takes longer to get the coolant all the way out. But you don't need to change any gaskets.

Started out black suggesting someone(probably a oil change tech) mixed a bit of orange with the green.