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5th chapter in kids cars: the budget GTP!

Blue85

Blue85

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As the closing post of chapter 3 https://ck5.com/forums/threads/the-equinox-baby-black.349545/post-4415451, I previewed the next junk driving home.

20250609_181806.jpg

So everyone here is in on the ground level of troubleshooting this thing. 2004 SC 3800 (it's not even my fault these things follow me home).

Main issue is cooling/ leak. The car kind of wants to overheat. The coolant temp is all over the place while driving, like up to 220, then down to 190. There are obvious signs of coolant on both front and rear of the engine. Sometimes the engine is hot and the upper rad hose is almost collapsed. The lower hose is warm, but air from the fans is not very warm. I see no vapor from the tailpipes and can't smell coolant in the exhaust, but there is a bit of condensation in the oil fill cap. Opening the bleed screw on top of the thermostat bleeds out coolant right away.

So, intake gaskets, head gaskets, cracked head(s)?

It kind of acts low on coolant, but the heater is always full. The radiator cap is lower than most of the reservoir, so opening that just spills coolant on the ground, not back into the radiator. I suppose I could pull the thermostat to see what happens. I kind of want to run the garden hose through the rad to make sure it's not plugged.
 
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It came home with no blower belt (what's the point of a GTP?), but I was able to fix the seized idler pulley in a few minutes with parts on hand (guess I didn't fully purge my 3800 parts years back?), but I don't want to put the belt back on until the basics are addressed.

Honestly, this is the first time I ever drove a super 3800 without a blower belt, and it does behave surprisingly like a normal car for the lame intake restriction on it. I assume this is why the fuel trims are negative everywhere, which makes me want to put a belt on (I probably have one) to verify the trims look normal and that there aren't issues with the supercharger. We're probably not paying the registration and putting her on the road until these issues are figured out. It should be no problem to get her $400 investment back!
 
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What's the best order of testing here?
  1. Get a new radiator cap (or check the stash)
  2. Pull or swap the thermostat
  3. Assemble a leakdown tester
  4. Get coolant to a level it can run with the cap off to look for bubbles
  5. Get a leak detector kit https://www.amazon.com/RELD-Gasket-Tester-Combustion-Detector/dp/B07RS3N98V?
  6. Start tearing it apart. If nothing else is obvious on the way, pull the heads. It's like $140 for a full top-end gasket set.
The coolant sitting on the intake makes me think the intake gaskets are bad. A failure there could also let manifold vacuum suck on the coolant, explaining the hose seemingly wanting to collapse. Also, the upper hose seems a little long, like, it's being forced to fold. I might cut an inch or two off to see if it stays more round.

I could chance it by replacing the intake gaskets, thermostat, radiator cap, clean/flow test the rad and then see whether or not it looks like there's additional issues. I haven't even checked that the manifold bolts are tight yet.
 
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Are you getting coolant flow? I'd throw a thermostat in it if it's not hard too change. Maybe pull a heater hose and run it with straight water in the system and see if it's flowing. My kids truck just had a water pump impeller fall off and it would run hot but the heater hoses would not heat up due to no flow.

Napa sells a combustion tester like that one you linked that I've had good luck with.
 
The heater works great, so there is circulation there. My progress today was to dump the coolant, swap the radiator cap, refill and test. The reservoir was full of some copper stuff, presumably some kind of snake oil to "fix" the leak. The rad itself was definitely low when I started. The garden hose rushes through the block and the radiator as fast as I can deliver, so they're good enough at this point.

20250602_191550.jpg

On warm-up not much was happening. A few air bubbles came out, but that's to be expected having just opened everything. As the engine gets hot, the bubbling to the overflow increases, eventually becoming almost constant. Grabbing the upper rad hose with a rag, the bubbling is easily felt (just after the T-stat). I was thinking head gasket for sure, but after shutting off the engine, you can hear it gurgle for several to dozens of minutes with the same pulsing in the radiator hose. In my mind, that can only be boiling. The temp is above the boiling point of water, so the only defense would be pressure. So something must be leaking?
 
Blue85 said:
As the closing post of chapter 3 https://ck5.com/forums/threads/the-equinox-baby-black.349545/post-4415451, I previewed the next junk driving home.

So everyone here is in on the ground level of troubleshooting this thing. 2004 SC 3800 (it's not even my fault these things follow me home).

Main issue is cooling/ leak. The car kind of wants to overheat. The coolant temp is all over the place while driving, like up to 220, then down to 190. There are obvious signs of coolant on both front and rear of the engine. Sometimes the engine is hot and the upper rad hose is almost collapsed. The lower hose is warm, but air from the fans is not very warm. I see no vapor from the tailpipes and can't smell coolant in the exhaust, but there is a bit of condensation in the oil fill cap. Opening the bleed screw on top of the thermostat bleeds out coolant right away.

So, intake gaskets, head gaskets, cracked head(s)?

It kind of acts low on coolant, but the heater is always full. The radiator cap is lower than most of the reservoir, so opening that just spills coolant on the ground, not back into the radiator. I suppose I could pull the thermostat to see what happens. I kind of want to run the garden hose through the rad to make sure it's not plugged.
Click to expand...
I had to do a few of those intake gaskets.
If there's coolant or water in the oil pan but not milky and no vapor from the exhaust it's the intake gasket
 
Went to ZZP for the Garloc gasket because they're basically reusable, rather than spend the same/more on a paper gasket. Have a new set of intake gaskets on the way. I'm gambling that I have enough injector O-rings on hand to replace any needed. Meanwhile we can do some more investigation. If that's inconclusive, we can go just as far as gaskets and try it, since that job is not super hard and taking it apart again soon won't scrap the gaskets.

1748968617884.png

Good news is that this car has the aluminum engine cradle.
 
Blue85 said:
The heater works great, so there is circulation there. My progress today was to dump the coolant, swap the radiator cap, refill and test. The reservoir was full of some copper stuff, presumably some kind of snake oil to "fix" the leak. The rad itself was definitely low when I started. The garden hose rushes through the block and the radiator as fast as I can deliver, so they're good enough at this point.

View attachment 505425

On warm-up not much was happening. A few air bubbles came out, but that's to be expected having just opened everything. As the engine gets hot, the bubbling to the overflow increases, eventually becoming almost constant. Grabbing the upper rad hose with a rag, the bubbling is easily felt (just after the T-stat). I was thinking head gasket for sure, but after shutting off the engine, you can hear it gurgle for several to dozens of minutes with the same pulsing in the radiator hose. In my mind, that can only be boiling. The temp is above the boiling point of water, so the only defense would be pressure. So something must be leaking?
Click to expand...
I suggest a real good flush and fill with water then do a leak down test of the cooling system.
If you are loosing pressure then do the fumes test to see if you are getting combustion gasses in the cooling system
 
We tore the intake off this weekend and the LIM gaskets are as bad I expected. The seals around the coolant ports were dissolving. Compression looks good, but we may have to repeat it, as we were pulling the plugs one at a time on the way around. Unfortunately, we didn't do leak-down testing prior to tear-down, so at least partial re-assembly would be required to do that. So we've discussed moving forward and pulling the heads, or re-assembly to re-evaluate after the smoking gun has been fixed.

20250609_181701.jpg

It was clear that coolant had been seeping up the manifold bolts and from the gasket area. The firewall/heater hoses are slimy and there's there was coolant puddled on the front of the intake before we started. Really the whole engine is kind of blacked up with coolant gunk. The good news is that this one already got the metal coolant elbows.

She got her hands really dirty and we had a good afternoon in the garage!
 
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You can do leakdown without an intake manifold, unless you pulled the rocker arms?

Is that one of the engines with the nylon cam sprocket teeth that will need replaced?
 
folkenheath said:
You can do leakdown without an intake manifold, unless you pulled the rocker arms?

Is that one of the engines with the nylon cam sprocket teeth that will need replaced?
Click to expand...
It's just hard to tell if small leaks are between cylinders or to the water with no intake or water.

Valvetrain in these is pretty robust. I mean, we all know it could use a bigger cam, but I've asked her kindly to avoid zzperformance.com. Head gaskets are also rare failures, but there's no way for us to know the history of overheating.
 
Blue85 said:
It's just hard to tell if small leaks are between cylinders or to the water with no intake or water.
Click to expand...

At that point you would probably be pulling the heads either way so I say test it and see.

Blue85 said:
Valvetrain in these is pretty robust. I mean, we all know it could use a bigger cam, but I've asked her kindly to avoid zzperformance.com. Head gaskets are also rare failures, but there's no way for us to know the history of overheating.
Click to expand...

Was it the older 3800 that had the nylon cam sprocket teeth?
 
I wanted to correct myself because actually sometimes it's easier to do a leakdown test with the rocker arms off because if the pressure rotates the engine it doesn't open the valves and then you start over.

Obviously compression test can't be done that way.
 
folkenheath said:
I wanted to correct myself because actually sometimes it's easier to do a leakdown test with the rocker arms off because if the pressure rotates the engine it doesn't open the valves and then you start over.

Obviously compression test can't be done that way.
Click to expand...
I was about to make the comment but you saved face before I did. :D
 
Compression is 160-170 across the 6
(L32 is like 8.5:1). Leakdown shows nothing really between cylinders. They all hold pressure. Right now I'm not thinking of a more fine tooth comb for head gasket failure. When it's back together we can test the coolant for combustion byproducts.

Onward!
 
The pitting from air + Dexcool is pretty bad. I'd like to source a new intake, but we'll probably skim it with silicone. The iron is way less affected.

20250610_200723.jpg
 
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