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Cooling System Overhaul - Stumped and Frustrated

1-2 PSI over about 20 minutes.

Ive got a bit of coolant seeping out of the heater hose splitter for the rear heat, and a bit more seeping out the bolt threads at the thermostat neck.
 
Have you pulled out the thermostat and tested to make sure it works? You could boil a pot of water on the stove, then toss in the tstat and see if it expands/contracts.

Also, does your water pump have fins, or a wheel that pushes the coolant?
 
clandr1 said:
Have you pulled out the thermostat and tested to make sure it works? You could boil a pot of water on the stove, then toss in the tstat and see if it expands/contracts.

Also, does your water pump have fins, or a wheel that pushes the coolant?
Click to expand...

Yep, i've tested and swapped tstats a number of times now.

The current one has been tested. Its a high flow that i got from a member here. I'm sure the part number is listed here somewhere.

Water pump is a delco HD unit. Nothing too special. Recommend a better one?



After some further measuring, fans won't fit in front of the coolers, and really, shouldn't be needed.

The champion radiator i have is rated to "900 hp" , and the only bigger one they offer for my truck is the 4 core, which is rated for "1000 hp". Not that i believe those numbers, but as a comparison, i doubt its worth it to step up to the 4 core. there HAS to be another problem.
 
47 pages of stuff here, I don't remember reading anything about it as the thread was growing, did you end up replacing the engine... I would think with 250k miles, there's probably something internal going on causing this and you have pretty much spent as much on cooing items and that high dollar radiator, you could have had a new engine rebuilt for it.

If you did, there's still something wrong in the engine setup.

I'd be yanking it out. too much crap going on here with a simple cooling system to deal with this much headache over.
 
dhcomp said:
Yep, i've tested and swapped tstats a number of times now.

The current one has been tested. Its a high flow that i got from a member here. I'm sure the part number is listed here somewhere.

Water pump is a delco HD unit. Nothing too special. Recommend a better one?



After some further measuring, fans won't fit in front of the coolers, and really, shouldn't be needed.

The champion radiator i have is rated to "900 hp" , and the only bigger one they offer for my truck is the 4 core, which is rated for "1000 hp". Not that i believe those numbers, but as a comparison, i doubt its worth it to step up to the 4 core. there HAS to be another problem.
Click to expand...

Sorry man, I'm out of ideas. I will say that my '89 w/ bone stock 350 runs perfectly cool with regular ole NAPA parts (water pump, tstat and radiator) so I'm in agreement with 4xcrazy that it is most likely a motor issue, not a cooling issue.

Is the coolant mix 50/50?
 
4xcrazy said:
47 pages of stuff here, I don't remember reading anything about it as the thread was growing, did you end up replacing the engine... I would think with 250k miles, there's probably something internal going on causing this and you have pretty much spent as much on cooing items and that high dollar radiator, you could have had a new engine rebuilt for it.

If you did, there's still something wrong in the engine setup.

I'd be yanking it out. too much crap going on here with a simple cooling system to deal with this much headache over.
Click to expand...

No worries on not reading the thread. its long :doah:

Yes, i replaced the motor. About 15k on it since last year.

New GM Crate motor, stock intake manifold, Delco water pump, delco HD fan clutch, new hoses, high flow tstat.

Stock oil cooler in front of radiator on drivers side, identical cooler on passenger size for trans. Stock a/C setup.

Champion 3 core all aluminum radiator.


I REALLY don't want to do a swap again. What would cause a motor to heat up like this?

I've got a adjustable fuel pressure regulator setup on it, but its running at 12 or 13psi. Shouldn't be running lean.....which is the only other cause i could think of.

Antifreeze is about 50/50. I'll check again tonight to confirm, but its definitely close.
 
Are any of the coolant additives worth using?

Redline Water wetter type products?
 
If you lose any pressure, there is a leak, but 1-2psi over that period is likely not much more than what you know is already an issue. I've only used one of these testers over a short period, but once I got the leaks sorted out (loose clamps in a couple of spots) it held the same pressure for over 45 minutes. For all I know the pressure tester itself could be an issue, but I didn't have that problem.

You'd want to check cold, since the checker is "sealing" the system, any decrease or increase in coolant temp from when you start measuring will affect the pressure reading.

While I've seen people run with no pressure in the cooling system for specific reasons, and I've never seen an overheating issue caused by it...the loss of pressure means the coolant will boil at a much lower temperature, which can cause localized boiling (at the cylinders) and that could theoretically cause temp issues. I don't think that is your case, if it will hold pressure, even if it leaks down a bit over time, it's not going to be the issue here. But more pressure is better for this reason.

Sort out the known leaks, then hit it again with the pressure tester. I'd run it over 15PSI (30 was max on the one I had) for testing, if something blows at 20-25PSI, it was a weak component anyway. I would try to reference coolant level before the test, then let the system sit with pressure for 30 minutes+, and note not only what final pressure was, but coolant level as well. If you lose any coolant, it's going somewhere. The longer you let the pressure work, the more likely you are to find where the coolant is going.

Didn't you have the same problem before/after the motor swap? I'd love to blame it on running lean under load because it's not the same cam/exhaust/whatever, but that wouldn't explain the same issue with a previous motor. You have an adjustable AFPR...any reason you can't temporarily crank it up to 14-15PSI and see what happens under a high load situation? It would be interesting to see if that influences your cold idle issue as well.
 
dyeager535 said:
If you lose any pressure, there is a leak, but 1-2psi over that period is likely not much more than what you know is already an issue. I've only used one of these testers over a short period, but once I got the leaks sorted out (loose clamps in a couple of spots) it held the same pressure for over 45 minutes. For all I know the pressure tester itself could be an issue, but I didn't have that problem.

You'd want to check cold, since the checker is "sealing" the system, any decrease or increase in coolant temp from when you start measuring will affect the pressure reading.

While I've seen people run with no pressure in the cooling system for specific reasons, and I've never seen an overheating issue caused by it...the loss of pressure means the coolant will boil at a much lower temperature, which can cause localized boiling (at the cylinders) and that could theoretically cause temp issues. I don't think that is your case, if it will hold pressure, even if it leaks down a bit over time, it's not going to be the issue here. But more pressure is better for this reason.

Sort out the known leaks, then hit it again with the pressure tester. I'd run it over 15PSI (30 was max on the one I had) for testing, if something blows at 20-25PSI, it was a weak component anyway. I would try to reference coolant level before the test, then let the system sit with pressure for 30 minutes+, and note not only what final pressure was, but coolant level as well. If you lose any coolant, it's going somewhere. The longer you let the pressure work, the more likely you are to find where the coolant is going.

Didn't you have the same problem before/after the motor swap? I'd love to blame it on running lean under load because it's not the same cam/exhaust/whatever, but that wouldn't explain the same issue with a previous motor. You have an adjustable AFPR...any reason you can't temporarily crank it up to 14-15PSI and see what happens under a high load situation? It would be interesting to see if that influences your cold idle issue as well.
Click to expand...

Thanks for the response.

I'd love to watch coolant level, but i can't really do that. I put the tester on with a full radiator, but when i release pressure, i lose some coolant out the top. The way the pressure tester is setup, it doesn't go into the overflow tank.

I can definitely crank the AFPR up again. I had played with it closer to 14-15, and when i saw no real performance gains, i put it back down. That being said, this was on the first motor.

As for the rough idle, i'd guess i've got some sort of a cold vac leak associated with the intake. Its the only part that really transferred over that would cause that.

Yes, i had similar cooling issues on the previous motor, but not the spikes i was noticing before the tstat opened. Since getting away from the real temp spikes, the motor running a bit hot has been pretty consistent.

The old motor didn't run hot as consistently, but got hot under load at about the same rate.

I'll do what i can to stop the few little leaks I have, and see if it will hold pressure longer.

At this point, the main thing i wanted to check was if i had a big coolant leak on the intake manifold. And it doesn't seem that is the case.
 
That an AL or iron intake? I've not really heard of problems with the stock intakes, but I have a buddy that has a cracked Edelbrock up near the thermostat housing. But his leaks coolant.

If it was sucking in extra air through a vac leak, it would run lean during open loop (cold, heavy throttle). If an external leak, you should see the change in idle quality if you use some sort of combustible to spray the intake while it's running. I haven't done it, but I would think an unlit propane torch to be about the cleanest way to test for a vacuum leak.

From what I've seen, the exhaust manifolds will also glow if it's running lean, but it would have to be immediately after running it hard, and dark enough to see if they are glowing.
 
Stock intake.

no noticeable coolant leaks. I've run this thing hard, and never saw glowing exhaust. That being said, i'm running Flowtech shorty headers.

Good call checking the intake for leaks again with propane.

The only time i have a rough idle is when cold. But, given that its a new motor, it should run like new if everything is functioning as it should.
 
I often suspected a cracked intake as a cause of my problems on my old tbi 350. I always wanted to grab a junkyard one and throw it on.
 
This is a long shot,but I've heard of one engine my friend worked on that had the EGR passages in the intake crack,and it had a rough idle until it warmed up (and the manifold likely expanded enough to seal up the crack some?)..so the exhaust gasses were being mixed in with the fuel air mixture ,just as it would be if the EGR valve was open...(though probably not as much)..

--the engine also had an off idle stumble, and was brought into a shop when it started running too hot on hot summer days with the A/C on--in cool weather it ran OK,other than the rough idle after a cold start ,till it warmed up.....the mechanic noticed after a highway trip long enough to get the temp gauge to read high,(but not peg the needle)-and it started running rough again,like it was at idle after a cold start..like it had a skip or fouled plug..he noted some of the plugs had carbon deposits,and others looked white,like it was too rich in some cylinders,too lean in others..

How he determined the intake was cracked I dont know,maybe he used a vacuum gauge or a smoke machine,or was just guessing??..--after replacing the intake with a salvage yard one,the engine idled smoothly when started cold,and though the temp gauge didn't go down that much at high speeds with the A/C on,it never got hot enough to peuke into the overflow tank,so he called it "fixed"...figured the gauge was not accurate or maybe the sending unit's calibration was off some..he may have used the injectors off the salvage yard engine too..
 
Kinda what i'm worrying it happening inside my intake.

I REALLY don't want to reseal it again without putting on a new intake manifold.

I resealed it twice on the old motor, and then installed on the new motor. If i'm taking the time to do it again, i'm putting on a new intake.

Do you guys recommend stock, or step up to an edelbrok performer tbi setup?
 
Who sells stock ones new? Haven't been able to find one. And, for something this labor intensive to swap out, i'm not going used.
 
Ok guys. You know my ability to lean towards new stuff to fix unknown problems.

Plan seems to be to do a bit more testing, and see if i can find any external intake leaks.

Then, it sounds like i'm going to try out a new intake. I have time for one "significant" project before I start towing at the end of the month.

Going to get the edelbrock TBI non air gap manifold, felpro gaskets, UltraBlack Permatex to seal around coolant passages, proper thread sealer for bolts near coolant passages, and The Right Stuff gasket maker for the ends.

Anyone have a comprehensive list of other hardware i'll need? In the past, i've reused all the mounting bolts. Figure i Just need new studs for things like the water neck.


Overall goal here is to remove cold start rough idle, and finally get this thing to run/cool properly.
 
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