S-10 Forum banner
1 - 20 of 22 Posts

·
Registered
1989 S10 Tahoe - Single Cab / Long Bed - 4.3 TBI / 700R4 4WD - 3.73 Detroit Truetrac
Joined
·
9 Posts
Discussion Starter · #1 ·
Hey everyone,

My '89 4.3 4wd pickup has been running a little hot these past few summer months and I was wondering if any of you had any insight on my problem.

A little history on the vehicle - I bought the truck with a blown motor about 7 years ago and rebuilt the 4.3. Then I added an aux trans cooler and got the AC working and converted to r134a. I don't tow all the time, but I do pull a small pop-up every other month or so. I also do a bit of mild wheeling, nothing crazy though.

There are two possible causes I have been thinking of - I did swap the cluster back to its original digital dash because I wanted my tach back, and added a factory oil cooler around the same time. Ever since then it seems like the ECT has been sometimes reading just under the "danger zone" with the AC on during freeway driving or extended idle. It doesn't do this all the time, sometimes it will stay right at the halfway mark (200F) and stay there for the duration of the drive, even with the AC pumping.
I actually had to shut it off once because it got in the red on a mid 80s day idling in a parking lot. After letting it cool off for a bit, I started it up with the heater on full and the temp came down to normal and stayed there. I haven't run the AC while stationary for more than a couple minutes since then.

I have since replaced the thermostat and ECT sensor with new GM parts to no avail. There are no external coolant leaks and I have no reason to believe it's burning coolant either - the last couple oil changes have looked good and I'm not losing any coolant.

Is it possible with the trans & aux cooler, condenser, AND factory oil cooler I'm decreasing the efficiency of the rad too much? The aux cooler is the only part that's not factory on this setup. I'm not sure if the oil cooler was optional on the '89 MY, the car I took the parts off of was a '93 with the early vortec, while I have a TBI. If it came down to keeping one or the other, I'd opt for the aux cooler.

I have thought about plugging off the oil filter adapter inlet/outlet to the rad and seeing if this makes a difference.
I have also wondered if the digital dash is reading high. It's a little hard to tell with the digital blocks, but it seems like at its hottest it will sit at about 216-230F. I don't have another vehicle to compare it to, but this just seems too high to me.

I think I'm going to start with putting a thermocouple in place of the factory ECT in the intake and see where the temp is actually at. Has anyone had any issues with digital clusters reading off? Is there anything else I may be missing here. Sorry for the novel, I just wanted to cover all the bases. Any and all help is greatly appreciated!

Thank you,

Alan

Tire Wheel Vehicle Hood Automotive tire
 

·
Registered
Joined
·
12 Posts
Are you using the water pump driven radiator cooling fan?

If so, if yours has the thermal factory fan clutch, the fan clutch may be worn out and not locking up to suck enough air thru the A/C condenser and engine radiator?
 

·
Been there Done it
Joined
·
12,474 Posts
Is your shroud in place properly?
 

·
FLORIDA BUTCH
Joined
·
111 Posts
200 degrees is the limit. New trucks run at 200. I wouldn't run mine at 200 degrees. Mine never goes above 190 degrees, on a hot day. I like it to run between 170 and 180 degrees. 200 is too high.
 

·
Registered
1989 S10 Tahoe - Single Cab / Long Bed - 4.3 TBI / 700R4 4WD - 3.73 Detroit Truetrac
Joined
·
9 Posts
Discussion Starter · #5 ·
I believe I replaced the fan clutch during the rebuild as it looked to be the original, that was a while ago though... it does seem to kick on, it roars pretty loud, especially in first gear like most of the S dimes I've been around. Might be worth taking a closer look at. Also my shroud is in place as well as the air dam. Are any of you running 180* thermostats? I have an ACDelco 195* currently. Not sure if it would be worth trying a lower temp.
I also just noticed my condenser has quite a few good sized bugs wedged in it. Might try hosing it down and seeing if that makes a difference.
 

·
94 4x4,01 Blazer
2001 Blazer 4dr 4wd LT
Joined
·
1,608 Posts
1- our s10 are DESIGNED to run 190-200, hence the 195thermo. 2- Have you flushed your coolant ? old antifreeze and or mixed will not react correctly.Flush your system and refill correct mix.3- as Slayer mentioned- is your shroud intact and is the radiator clean? dirt,leaves and bugs are no help.4- are you Hoses spongy- they can collapse and cause issues.5- got a scan tool? check to see if you sensor(s) match-there is one that drives the gauge and one for the computer.
 
  • Like
Reactions: alanjd93

·
Been there Done it
Joined
·
12,474 Posts
Since it primarily happens when stationary, it's definitely somehow related to the fan. Or more correctly the trucks ability to create it's own air flow thru the rad. Since you've pretty much eliminated the fan and the shroud, I'd take a good look between the condenser and rad for dirt and debris.
The other possibility is the rad is getting clogged internally from corrosion. A 32 year old rad could just be losing it's efficiency. The're not super pricey, so get a good one.
Question. In the pic above the rpms are at 1750. Does it idle that fast or were you revving it a bit to increase the air flow thru the system?
I've got a 10 year newer version of the same truck. 1999 Reg cab Longbox 4.3 4wd. In the 2nd gens that combo is extremely rare. My A/C wasn't working when I bought it and getting it going is a ways down on my list. Here in the frozen tundra it's not as important as in other places. Someday.:unsure:
 
  • Like
Reactions: alanjd93

·
Registered
1989 S10 Tahoe - Single Cab / Long Bed - 4.3 TBI / 700R4 4WD - 3.73 Detroit Truetrac
Joined
·
9 Posts
Discussion Starter · #8 ·
I actually snapped that picture while on the freeway (against my better judgement) so what you're seeing is 4th gear at about 65. It seems like the only time it actually gets that hot is during higher RPM driving or a standing idle because yesterday afternoon I was running errands, mostly on 55 MPH country roads, and it never got up above the halfway mark. It usually stays around 750 RPM at idle. In have been thinking of replacing the radiator too, if anything just as a preventative measure. I might just bite the bullet on one sooner than later if cleaning out the fins doesn't make a difference. Not sure of the condition or age of the current rad, but being a 30 YO truck it may be well past its intended lifespan.
And here I thought Michigan winters could be brutal... I'm not sure I'd be equipped to live in the tundra :eek:
 

·
Registered
1989 S10 Tahoe - Single Cab / Long Bed - 4.3 TBI / 700R4 4WD - 3.73 Detroit Truetrac
Joined
·
9 Posts
Discussion Starter · #9 ·
I had the coolant completely emptied when I did the rebuild - I pressure washed the water jackets in the block/heads and the machine shop hot tanked them after that. I also replaced the water pump and all the hoses on the engine as well as the heater core since it was leaking when I bought it. 50/50 mix of fresh prestone green went in. As for the rad, I just looked at the back side of it while cleaning out all the bug and road debris, and it definitely looks like some of the fins are folded in on it. This just reaffirms it's probably time... For the time/effort to remove it and try to sraighten them out I'm better off getting a new one.
I don't have a scan tool on hand that does live data for OBD1, just a "code reader" that jumpers the pins at the DLC. Might be worth seeing if there's an old Tech 1 I could dust off and borrow from work.
Thanks for all the advice!
 

·
Registered
Joined
·
12 Posts
It sounds like you have been quite complete and thorough in your problem solving.

If the fan clutch is locking up and sucking a lot of air thru the radiator when hot, if the fan shroud is in place, perhaps another radiator is called for?

 

·
Registered
2003 GMC Sonoma SLS extended cab 4.3L auto 4x4
Joined
·
324 Posts
It sounds like you have been quite complete and thorough in your problem solving.

If the fan clutch is locking up and sucking a lot of air thru the radiator when hot, if the fan shroud is in place, perhaps another radiator is called for?

It sounds like you have been quite complete and thorough in your problem solving.

If the fan clutch is locking up and sucking a lot of air thru the radiator when hot, if the fan shroud is in place, perhaps another radiator is called for?

I might suggest caution about parts from E Bay. There are known cases where they are inferior quality or you end up with an 'equivalent' part. I'd shop around at other more reliable sources, and I'm sure others on this forum may have some solid resources to offer.
 

·
Registered
1989 S10 Tahoe - Single Cab / Long Bed - 4.3 TBI / 700R4 4WD - 3.73 Detroit Truetrac
Joined
·
9 Posts
Discussion Starter · #13 ·
Screenshot Font Technology Electronic device Multimedia


Just checked The Rock and not too bad for GM genuine... I looked into an OEM fan clutch too. Mine seems to be working as far as I can tell, but I'm not so sure I ever replaced it after all... I looked through all my old emails and paper receipts and didn't find anything. Figured it might be worth a little peace of mind, especially if I'm pulling the fan and shroud off to get to the rad anyway. I think I'm gonna ground the truck till I can order these up next paycheck. A little more than I was hoping to spend, but a lot better than blown head gaskets and/or toasted bearings.

Thanks again for all the advice! I've had a lot of other projects going on simultaneously, so I really appreciate all the brainstorming. I'll keep you updated when I get the parts swapped.
 

·
Registered
Joined
·
12 Posts
View attachment 351288

Just checked The Rock and not too bad for GM genuine... I looked into an OEM fan clutch too. Mine seems to be working as far as I can tell, but I'm not so sure I ever replaced it after all... I looked through all my old emails and paper receipts and didn't find anything. Figured it might be worth a little peace of mind, especially if I'm pulling the fan and shroud off to get to the rad anyway. I think I'm gonna ground the truck till I can order these up next paycheck. A little more than I was hoping to spend, but a lot better than blown head gaskets and/or toasted bearings.

Thanks again for all the advice! I've had a lot of other projects going on simultaneously, so I really appreciate all the brainstorming. I'll keep you updated when I get the parts swapped.
It seems like a fan clutch will stop working (when worn out) and freewheel when the engine is hot......the very time you want it to lock up and suck gales of air thru the condenser and radiator!

If you replace the fan clutch when installing a new radiator (As I would, the ideal time to easily get at it), make sure you buy a thermal fan clutch and not just a rev limiting fan clutch.
 

·
Registered
1989 S10 Tahoe - Single Cab / Long Bed - 4.3 TBI / 700R4 4WD - 3.73 Detroit Truetrac
Joined
·
9 Posts
Discussion Starter · #15 ·
It seems like a fan clutch will stop working (when worn out) and freewheel when the engine is hot......the very time you want it to lock up and suck gales of air thru the condenser and radiator!

If you replace the fan clutch when installing a new radiator (As I would, the ideal time to easily get at it), make sure you buy a thermal fan clutch and not just a rev limiting fan clutch.
Ok, I verified the GM is a thermal type. I'm definitely going OEM with the rad, but do you have any opinions on 4 Seasons/Hayden fan clutches? They seem to stick in my mind as a good brand - maybe an OE supplier? They offer a Hayden severe duty for less than half the price of the GM. It's a thermal type as well. Anybody run one of these with good luck? With the cost savings I may as well throw a Gates water pump on it too. Might be overkill but I only want to have this thing apart once and want it to run coooool 😎
 

·
B4U Task Force Admin
Joined
·
30,359 Posts
Ok, I verified the GM is a thermal type. I'm definitely going OEM with the rad, but do you have any opinions on 4 Seasons/Hayden fan clutches? They seem to stick in my mind as a good brand - maybe an OE supplier? They offer a Hayden severe duty for less than half the price of the GM. It's a thermal type as well. Anybody run one of these with good luck? With the cost savings I may as well throw a Gates water pump on it too. Might be overkill but I only want to have this thing apart once and want it to run coooool 😎
I've used 4 Seasons products with success. As long as you're at it...I'd replace the water pump also...cheap insurance, and it will be out in the open.
 

·
Registered
Joined
·
12 Posts
I have received excellent service from the Hayden thermal fan clutches on various cars and trucks. I rate them the equal of OEM/factory fan clutches; at much less money (as you have noticed).

#IDK where you live; but here in Hot & Humid New Orleans I run a 180 degree thermostat in every vehicle I can. We can use the A/C 11 months out of the year; just for humidity control if not also temperature regulation. The extra 15-20 degrees cooler temperature makes a difference in the 5 months a year that the locals refer to as "Summer".
 

·
Registered
Joined
·
297 Posts
It may be worth checking your radiator cap. If the system can't build pressure it can't increase the boiling point of the coolant. Overheating is just one of multiple symptoms for a bad cap though.
 

·
Registered
1989 S10 Tahoe - Single Cab / Long Bed - 4.3 TBI / 700R4 4WD - 3.73 Detroit Truetrac
Joined
·
9 Posts
Discussion Starter · #19 ·
It may be worth checking your radiator cap. If the system can't build pressure it can't increase the boiling point of the coolant. Overheating is just one of multiple symptoms for a bad cap though.
I forgot to mention, I actually just replaced this a few months back when I did the T-stat and ECT. Thank you for the advice though, I forgot to put that in the original post.
 

·
Registered
1989 S10 Tahoe - Single Cab / Long Bed - 4.3 TBI / 700R4 4WD - 3.73 Detroit Truetrac
Joined
·
9 Posts
Discussion Starter · #20 · (Edited)
Well looks like I have a development in my predicament... I was finally able to hook a tech 1 up to monitor the ECT. Looks like I have a pretty large discrepancy between the gauge reading and the actual ECT as read by the ECM. So seeing as I just replaced the sensor in the head I'm thinking the gauge is wacked out.

ECT at 187F, gauge shows over 210F
Product Communication Device Office equipment Telephony Gadget Vehicle Plant Car Automotive design Gadget

ECT at 200F, gauge shows 216-230F
Calculator Office equipment Gadget Input device Font Vehicle Gadget Electronic instrument Audio equipment Display device

ECT at 210F, gauge shows overheating
Calculator Product Office equipment Office supplies Gadget Vehicle Automotive design Gadget Display device Personal luxury car
 
1 - 20 of 22 Posts
Top