Yesterday I wrote an article about how my 1989 Chevy K1500 Silverado’s motor blew up. I had tried starting it, the engine revved high, and then it locked up. Thereafter, cranking the mighty 350 V8 yielded a horrible noise that sounded like internal damage. Well, last night I charged my battery, and while the Chevy still made that awful noise while cranking, it fired up! And once it was running, it sounded OK. And yet… now it’s overheating. Someone please help me understand.
For the most part, if something doesn’t pass the laugh-test, you should always be wary, which is why I maintained cautious optimism when I chucked my newly-charged battery into what I thought was a blown-up truck. You see, motors don’t just throw rods for no reason, and certainly not two seconds after startup.
With the new battery in, I turned the key and listened to the horrible mechanical grinding noise still present, and I thought it was over. The truck sounded like it was filled with marbles. But after enough cranking, and a bit of pedal, the motor fired up and started idling nicely! Listen to this thing:
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For those of you anti-Instagrammers, here it is:
I drove the truck around, filled it up at the gas station, and marveled at the wonder that is the Chevy V8 — never doubt a 350! America’s unstoppable powerplaint! And then I noticed the temperature needle climbing, so I shut her down.
What the heck?
I haven’t driven enough to categorize the overheat-condition; does it happen only under load? What about at idle? But what I do know is that I’m not leaking any coolant, my oil looks nice and clean, and… hmm, does the heater work? I did try to turn the heater on on my way back to the house to help the truck stay cool; it cranks hot so that tells me that it’s probably not the water pump?
I mean, maybe the pump broke apart?
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The pulley still feels reasonably tight (then again, I still have the belt on there)… I’m confused. What do we think might have caused this horrible noise, and how is it related to my overheat condition?
I was getting a stuck ignition switch issue, which I suspected might have caused the starter to hang up, creating that awful noise. And when you turn the ignition, the temperature does max out on the gauge until you let off the key, but while I was driving, the temp wasn’t at max, it was at 3/4, so I don’t think the ignition hanging up is the issue.
The truck now seems to take quite a few cranks to start. Don’t see any white smoke. Water pump doesn’t sound loud at idle… hmm.
Does anyone have any ideas? This is a strange one.
A new thermostat is the cheapest place to begin, followed by a rebuilt starter.
Despite the tee shirt graphic weird might not be good but it is definitely better than “blowed up good”.
As others have mentioned check the starter and flex plate gear.
I’ve cracked stock flex plates and they will make a racket, but usually that is due to abuse.
Run a cooling system pressure and temperature test. If the fuel pump is bad the beariing will leak, usually.
Check for all kinds of leaks, belts, pulleys and the harmonic balancer thing.
It’s a lack of attention causing this and somebody mentioned that you are an engineer specializing in cooling systems and it overheard that and here you go. Not entirely unexpected.
Good luck with it.
Wrote fuel pump meant water pump.
Yeaterday was an idiot day for me.
Have you tried turning it off and then turning it back on?
So you basically lied to Santa Monica police about that thrown rod. *shakes head
While I generally agree with K.I.S.S. in this particular case (a 36 year old computerized machine) it might be worth considering the complicated. They always told me in tech school, “it’s never the ECM.” Until its 30+ years old and it fails in strange ways.
It’s always something simple, sure TBI adds a layer of complexity but always start at the basics.
Check for obvious vacuum leaks, check your pulleys with the belts off, if the starter is easy to drop do that too and confirm it isn’t on the way out.
The comments on smog pumps, bad grounds and the ignition being a problem sound extremely valid to me as well.
We didn’t really get the GM TBI down here, we went straight from carburetor to multipoint EFI on the 304ci Holden V8 in the late 80’s so I don’t have any specific knowledge on that system.
Check the A/C clutch pulley as well. That’s what just broke on my truck a while back, made a terible noise. Pulley separated from its hub and was just flapping around making a horrible noise. If I turned on the A/C the pulley would jump back into place and the noise would go away for a bit.
If that’s what happened, it could be allowing the belt to slip, meaning the water pump isn’t turning like it should. You’d think it would yeet the belt, but mine never did. Just something else to check.
This has happened to me too. Except the belt did not last so then it was pretty obvious what was wrong.
Pull the starter, check to make sure the pinion gear is still tight to the shaft, and that the pinion shaft doesn’t have excessive play. Ensure the pinion shaft can still extend/retract freely.
Remove serpentine belt and spin the water pump – see how it feels. Perhaps the impeller has started breaking up. Although if it’s pulverized into fine dust from running by now, it may not feel abnormal. In my experience most vehicle’s starters are strong enough to overpower a seized pulley, however. I would also highly doubt a water pump instantly seizing would be able to stop a running engine without chucking the serpentine belt or having horrific belt squeal.
As far as the ignition switch hanging up in “start” theory: I say this one holds some water. On TBI Chevys, there is a wire that goes from the starter to the ECM (PPL/WHT Pin C9) on the ECM to put the computer into cranking mode. I don’t know what exactly cranking mode does on TBI chevy’s, but it’s possible it puts the IAC in a very far open position. So if the key hung up in “start”, it could have caused 1) the engine to continue revving high after start and 2) the starter pinion gear/shaft/overrun clutch to take a beating.
oooooooo that is an interesting theory. And IAC’s can get stuck open/closed, especially with age.
Almost 100% of the time a late 90’s/early 2000’s Ford would stall at idle, it was the IAC… and it happened to tons of them. How to diagnose quickly? Hit it with something hard, see if it stalls again. One time I “diagnosed” it by hitting it with my own shoe, worked.
Yes, during crank mode the IAC is commanded full open, to learn position, and then steps down based on the ECT reading.
Water pump. Cheap and easy to replace. KISS
I have an 88 C1500 5.7 that I have been going in circles troubleshooting for a few months now. This includes having a temp gauge that from time to time was reading warmer than it was. These trucks have two coolant temperature sensors. One is a two-wire sensor on the intake manifold that is for the ECM. The second is a single wire one on the driver side cylinder head between plugs 1 and 3 for the gauge. For me the temp gauge kept reading hot, but also all the gauges on the cluster were reading weird which led me to concluding it was wiring related and not a mechanical problem. Turns out there is a small ground strap that should go from the back of the passenger cylinder head (or in my case a trans bell housing bolt) to a stud on the cab. My ground strap was loose and after I got that tightened up the gauge was back to reading normal again. Since it is a one wire sensor it needs a good ground thru the sensor body/engine to work correctly.
Was the truck cold when you fired it up the other day? I can’t explain the engine revving when you started it, apart from possibly a big vacuum leak acting like the throttle being stuck wide open. Otherwise, it sounds like maybe the starter solenoid/bendix is sticking out and spinning with the flywheel.
Starter Kickback and overheating as symptoms. Headgasket-coolant in cylinder making the starter angry, low coolant in passages making the owner angry. Speculation though-Would definitely need more testing.
I would Google an exorcist near the Santa Monica area.
I don’t know about exorcists, but I used to know of a couple of witches that lived in Santa Monica. That was back in the 80s, probably still there.
You probably know this, but if you stick a piece of small hose against the water pump and the other in your ear, you can hear the offending part a lot better for purposes of troubleshooting.
If you stick a phillips head or other type of bit in the end of the hose you can transfer a lot more acoustics through the hose. If you add some metal to the other end that fits in your ears.. you have a cheap automotive stethoscope. You can buy some at Harbor Freight if you don’t want to make any.
I’ve used many iterations in my years wrenching.
I’m surprised how far down I had to go for someone to even mention the word thermostat in the comments.
Make sure it’s not stuck closed or partially stuck closed. Or just replace it if it’s easy enough to access. It’s probably older than you and the coolant is older than most internet celebrities.
Where is that Unsolved Mysteries guy when we need him?
Robert Stack played Ultra Magnus in the Transformers! He knows all about trucks! He was one!
Yeah he was. Unfortunately he was a terrible leader and gave up the Matrix/got blown to pieces (don’t worry, they fixed him with Bengay or some other weird liniment from the junkyard), but that’s not the voice actor’s fault.
My favorite Ultra Magnus quote from The Transformers: The Movie = “I can’t deal with that now”.
Good job robo-bro, we go from the ultimate leader in Optimus Prime to you spewing crap my mom would say.
https://youtube.com/shorts/cpBKJUOA_tU?si=uhxjcgEkYf6UOp89
I’m still a personal fan of “Open, dammit open!”
Yes, that one sprang to mind as well, haha!
He also knows a fair bit about Airplanes!
“The FAA…the airlines….they’re all a bunch of cheats and liars!”
If you have a scanner handy, check the engine temperature sensor reading. I had a 1995 K1500 that displayed a very inaccurate temperature, resulting in a high idle and stalling when in gear. If your sensor is reading incorrectly, that might explain the high idle and possibly the overheating warning. I checked and it appears the 1989 has the same type of sensor in the block.
Last couple of times i lost the water pump it made a distinctive sound as it shot the belt into the hood. 2nd time was a defective pump bending the shaft 3 ways so I got the enjoyment of swapping it in a Chinese restaurant parking lot. Thankful it was across from a parts so only a short walk in100f
Same car once needed me to hammer on the flywheel to turn it w pry bar as the starter extended with a tooth straight at a tooth on flywheel and jammed. Never removed flywheel or starter and started fine after.
So weird stuff happens and maybe it took two of them to really register?
Does this have an engine-driven fan like most longitudinal engines of the time? Is there something that got stuck between the radiator and the fan there that is hitting the fan, blocking part of the radiator, or causing it to slip sometimes, but maybe not all the time?
Like a cat with kittens?
I kid I kid.
Seriously though – I struggled with my LO5 overheating for almost a year before I realized I was an idiot and the electric cooling fan wasn’t coming on. If it kept over 25 mph there was no need for the fan anyway.
The cat thing (single cat) happened to my cousin in his Ford truck.
Hooray that its not a wrecked bottom end!
I’ve definitely had starter pull-back mechanisms, key return springs, and starter gears, fail and create all kinds of odd situations with bad noises and other odd happenings, so that’s for sure a place to consider. If the starter is staying engaged that could cause overheat but I’d think it would have burned up by now if it was truly still spinning.
Possible water pump issue? Sure, possible! They can make some real bad noises sometimes but it would be an odd failure that was that immense yet also didn’t start leaking coolant…
Keep us posted…
Not surprising. Chevys rarely elect a new pope on the first ballot.
Got-danged genius comment here!
I think that makes me want to nominate Bob Lutz as the next pope.
The odds of the events that had to occur simultaneously to make this comment work are truly astounding.
My money is on the water pump, David. I remember one day I was driving home in my 2009 Dodge Ram 1500 (while it was still Dodge but right at the cusp), I was coasting downhill to a stop. After I took off from the stop, I was half a block from my house and there was the most ungodly rattling, clanking, and pinging noise I ever heard an engine made. I was certain that I had blown the engine somehow, despite it having no warning signs prior. I was completely upset and distraught and my wife tried her best to console me. After feeling sorry for myself for awhile, I did some diagnostics where it was parked in the garage. After doing some testing, I found out it was indeed the water pump and not a failed 4.7 V8 (believe it or not). Luckily, there was no thermal event related to said failure.
I’d never been in a vehicle where one failed so spectacularly it created that cacophony of death rattles, but here we were. Long story short, I changed the water pump and it ran perfectly for many miles and years thereafter.
The problem is that now you are married, with a newish born kid and have something important to do, so even you realiable car will break for no apparent reason.
And then get back to work in the very same way.
My wife had her car totalled in an accident, and right after that (literally, a few hours later), my car started complaining about a bad fuel sensor, randomly stalling and with a rough idle. Couldn’t take it to shop because the car was not completely broken and need it to chaffeur wife and kids around.
What happened right after she bought a new car? The problem is gone and the car is working as before. Its condition improved over the weeks. No changes to be accounted for, fuel from the same gas station, etc.
The implicit joys that can be only attributed to marriage.
Glad your engine did not blew, maybe is the message from Automotive Gods saying to you realize the profit selling it and spending part of it taking Elise (NHRN) to celebrate that is not a loss and give her a couple of hours break.
“now it’s overheating. Someone please help me understand.”
Uh, weren’t you a cooling engineer on the Wrangler in a former life?
Oh, wait! Chevy! Yeah, I get it now.
Yeah, I’ll eventually diagnose the cooling system issue once I dig into it. But I wanted to share with y’all, because as yet, I don’t know how it’s connected to that horrible starting noise!
Maybe it isn’t, but that’s sort of the nature of the snowball effect – the more things go wrong, the more things go wrong.
It’d be great if you pinned a response at the start of comments so we’d know what you find. Or, I guess you’ll create a new article, which is cool, too. Let us know what you find. Thanks
I guess a few other people have said it, but it may not be the gauge. I’m wondering if all of your problems might be down to an over-voltage condition somewhere? I’d be inclined to look at the alternator, check voltages around the place, and make sure all the earths are earthing.
A couple of months after I got my Elise (with its famously fragile Rover K-series) it started to over heat. But the gauge was saying 999 degrees centigrade on its digital display, which for any one used to Fahrenheit is 899 degrees above the boiling point of water, and well over the melting point of aluminium.
Corroded earth strap.
Was that your car’s real name?
Mrs Tracey.
The 1998 Lotus Mrs. Tracey
Time travel IS real! 😉