New to me 99 Suburban: 5.7 vortec repairs


Picking up my 1999 Chevy suburban k1500 5.7 vortec, on Saturday. It has 202k miles, a rebuilt transmission and transfer case(4 years ago), new CV axle on pass side, and some new front end components: tie rods, etc. As far I know, the only KNOWN issues are a possible intake manifold leak ( unknown reason for missing coolant), and a front oil leak, possibly from front crank seal.

The previous owner has no knowledge of preventative maintenance or other types of repairs. I'm going to go ahead and do the intake manifold leak repair, and the spider injectors upgrade while I'm in there.

My question is, what other needed repairs/ preventative maintenance should I do while I have the engine available and a third vehicle to drive?

Thoughts so far:
Intake manifold
Spider injectors
Valve cover gaskets
Catalytic converter on left bank
Coolant flush with new thermostat and rad cap.
Change oil
Spark plugs
Diff gear oil change
Transfer case oil change
Water pump?
Crank seal?
Distributor rotor?
Check brakes

While I do work on my own vehicles, I've never messed with heads or block. Usually only repair normal wear and tear stuff like timing, water pumps, etc. I did rebuild a transfer case once!

If you were getting a used vehicle up to par, what would you do?
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Ducky's Dad

I have a '98 K1500 5.7. The intake leak is a known problem on those engines, requires RTV silicone sealant at the front of the manifold. Catalytic convertor failures are also common, mine got a new pair at about 125M. Front end components and shocks are worth re-examining, but the big problem with those trucks is the brake system. Lots of them came with undersized rear drums and the vacuum boost was inadequate for the weight of the truck, even when empty. If you have factory hydro-boost (unlikely on a 1500) then you are good to go with normal brake maintenance. I added hydro-boost to mine a long time ago, and went through several iterations of boosters, calipers, master cylinders, and pads before we finally got it right. Final solution was a boost pump off a one-ton milsurp truck, with 3/4-ton calipers in front, 3/4-ton master cylinder, and ambulance pads/linings all around. If you are planning to keep the truck, this is pretty much mandatory in my book. Best solution is to get a kit with all the details worked out for you. Factory brakes are so bad that I'm surprised there are so many of those trucks still on the road.

Other things that go bad are the radiator top tank (plastic, of course), and the rear differential. I have had to replace/rebuild the rear diffs on both my K1500s. One failed catastrophically (GM limited slip), the other gradually (G80 locker). If you hear a diff whine or a whump-whump, you are probably in trouble. Known problem on those trucks. Over all, a surprisingly good truck once you sort out the built-in defects.


replace the distributor when you do the intake. I had a 96' with a few less miles than that started really running like crap. turned out to be the bushings in the distributor allowing the rotor to wobble around.
I had to do the intake gasket on mine as well. flushed the hell out of it and went to green coolant.
about the brakes, I went to Praise Dyno pads and shoes and got decent performance, but everything i tried would not firm up the pedal.


What is the path forward on the rear diff? Mine is making some noise at 320k miles. 3.42 gears (I think) open diff.

Ducky's Dad

What is the path forward on the rear diff? Mine is making some noise at 320k miles. 3.42 gears (I think) open diff.
At 320K miles, you are ahead of the game. My cousin got over 400k on his with no failure, but that was all desert cruising, no traffic at all. The path forward depends on how it fails. One of mine grenaded at about 90k, destroyed the pumpkin and the axle shafts. I found a used, complete rear axle in the right ratio, and even with cross-country shipping, it was better than trying to rebuild the old one. There are wrecking yards that used to buy these axles by the boxcar load, because they could sell every one they had, but there none available when I had to find mine. The other one failed slowly, so I knew it was coming (lots of whump-whump noise from the diff on trailing throttle), and barely got to a shop before it left me stranded. Literally limped in to the shop at about 110k. They rebuilt it with new ring and pinion, and all new bearings. As I recall, they told me that the bearings in these diffs are the source of the problem. That was the one with the G80 locker, and it got used hard, still does.


Well we hit a snag. Went to pick it up and it won't start. I'm guessing fuel pump. Cranks, after about 10 seconds it will stumble, but won't actually fire up.

Current owner said he will take it to a shop and see what they have to say.

I'm not sure what to do at this point.

Ducky's Dad

I forgot to mention the fuel pump failure. Mine failed suddenly, running fine one minute then not at all. Those pumps are supposedly more sensitive than most to running on a low tank because they seem to need a lot of cooling. Replacement is a pain in the *** and not cheap. I think I paid maybe $800 about five years ago, plus the tow, so get that sorted out first unless the truck is very cheap.


Expedition Leader
If only there was a topic that already covers many of the typical faults in these vehicles.!-Sierra-pickup-Suburban-Yukon-etc

You've already covered most of the stuff. Full brake fluid flush would be a good idea too.

There is a 'new & improved' fuel injection spider that addresses issues in the 5.7 IIRC. 'not running' is awful convenient when selling a troubled vehicle. $25 will buy you an OBDII bluetooth dongle and the full version of the Torque app so you can scan for error codes. $50 will by you the cheapest scanner at Harbor Freight. Car doesn't have to be running to read codes, just switched on.


Update: "Suburban problem was distributor cap and rotor. Has been fixed"
I'll call the guy later and find out what actually was replaced.

I do have a code reader, it only threw a bank 2 o2 code. This is probably from the old injector system?

Also, that link above seems to only be for 2000+ models. But I'll look again.
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Expedition Leader
started out that way, but there are some other references and a lot of commonalities (like the intake manifold gasket issues on Vortecs. As well as some good advice about preventative maintenance and taking care of related components while you already have things apart to do something else. Will save you a lot of time, money and grief in the longer run.

intake and fuel delivery and cooling system corrosion issues are the main areas of concern with the earlier vortecs.

Find yourself the recommended 100,00k mi maintenance list and consider doing it all to give your vehicle a good baseline. Or at least using it as a priority inspection list. Comparison shop with online mailorder parts places like I was semi-shocked how much more I could be saving on parts. I've been a 'shade tree' sort of mechanic on my own vehicles and others' all my life, looking for ways to cut costs. Their prices were so much lower on some things that I regret not learning about them years ago.

Look at the 'how to' videos of, too. They're pretty straightforward and informative. If you are interested in doing some work yourself.