I think my lower radiator hose is collapsed
 

"New" block is in with re-worked head. Car runs great, gets up to 8psi on spring alone :-)
But I noticed that at apparently random intervals the engine would start overheating and just keep getting hotter. Had to shut it down and wait to cool off and then it would be OK for another hour or so. Until the temperature would rapidly just climb into high heavens again for no apparent reason.

Symptoms:
- Water temp needle stays pegged at 12 on the clock for extended periods. No variation whatsoever
- Then, seemingly out of nowhere the temp would start climbing and climb VERY fast until I shut off the engine.
- After shutting off and waiting maybe 5 minutes everything's OK.

So I did all the checks. Put in a new thermostat, new rad cap, flushed the system. No change.
Then I realized that it would only happen shortly after running high rpm (up to 7k)

And sure enough. Rev to 7K, then keep cruising at low rpm and maybe 15 seconds later, the temperature quickly runs up all the way. Just shutting down the engine for a few seconds while coasting and then re-starting fixes it and the temp goes back down!

So to me that sounds like a collapsed lower hose - right?

Replace 'em both. Cheap insurance.

Open the hood and look at it while you rev it?

My wife voted against it. She thinks our neighbors are car-hating sissies who wouldn't like the noise!

Well then you've got two options.

1. Divorce her and move out
2. Drive a couple of miles down the road away from the neighbors, then get out and rev it while you look at it

lol nothing worse than trying to help someone that doesn't even want to help themselves.

Interesting. I had these same symptoms up at T-Hill last time I was out, but I figured it was just regular old overheating.

1) Too expensive. And I kind of like her
2) That sounds too much like work. I'd have to get my behind off the sofa. Aaand the cops might disagree with my current blood alcohol levels.

I'll go for option #2, but in the morning when sober...

Preferably 5:30am.

Still drinking now. My brother is visiting. Don't think I'll be sober at 5:30!

Dang it all to heck. All hoses look nice and not collapsed at all while and after revving.
To add insult to injury, even at low rpm, without ever having revved above 5k, the engine is getting too hot when going up an longer incline on the interstate at 75mph in 5th. No boost. Turning on the heater full-blast helps getting the temp down. But that's a band-aid, not a solution.
The engine never overheated before, even in Miami summer heat. And the only thing that has changed is the new engine block and re-worked head.
When idling, I get nice, steady temperatures. After a few minutes the fan kicks in, runs for maybe a minute, then turns off. And again, and again.

Could it be running too lean or something with the timing?

Setup:
- '97 1.8l block, pistons, rods etc.
- Compression is 170-ish on all four
- '99 head with +1mm Supertech valves
- Stock ECU with FM Link piggyback
- T28, currently running at 9psi to red-line


What I've done:
- checked all hoses and replaced some
- replaced radiator cap
- replaced thermostat
- ran cooling system flush (I think it's citric acid)
- currently running 100% water with water-wetter

Other:
- Lower stock ducting is still in place, but hacked up to fit the IC
- No oil can be found in the water and no water in the oil
- outdoor temps are 60s. It's been fine before in over 100 without ANY problem

So I guess it's off to Autozone or Pepboys and see if I can rent a cooling system pressure tester.
Saturday is my Evolution Phase 1 AutoX training. Need the car reliable by then!

Could it be improper tuning either spark or fuel?

It appears this could be another one for the "epic fail" thread that faeflora proposed. Or just call me faestefan.....
Here we go. Go easy on the name-calling please:
It appears I installed the thermostat the wrong way round. Ouch. Stupid.

In my excuse, I installed it the same way round as the thermostat that was installed before. And I hired that mechanic for money!

So I thought about what could cause my symptoms and thought: Thermostat. But I replaced it and there was no improvement!
Then I remembered that it did seem odd- the way it was installed. Checked online and sure enough: Everybody else seems to install their thermostat the other way round...

Flipped it, went for a test-drive and before I could get 2 miles away, the Link-ECU died on me. Car is stranded now. Bloody-bleeding-goshdurn (&%*#&$#* ECU!

More tomorrow.

That'll do it. :P

The problem last night was not the Link ECU. It' a short somewhere in the 'engine' circuit.

See this thread: Electric Gremlins Thread