BlackBird71

My Firebird has an insidious overheating problem! All of the typical overheating causes have been checked and found to not be the cause. The solution will require "out of the box" thinking.

Specs:
1986
Vin H
4 barrel
5 speed
A/C (condenser removed)

For the first 14 years of ownership (purchased used in 1988) there were no overheating issues Temperature was well regulated at 195 in all conditions; idle, stop and go, hi-way, and up-hill.

For the last 8 years the symptoms are as follows:

Idle:
Temperature increases past thermostat opening to 240, fan kicks in at 238 (factory spec). Temperature then drops to 224, fan cuts off, (again factory spec). This heating/cooling cycle at idle continues and temperatures eventually creep-up to red line. Prior to this overheating problem, the temperature never went past 195 at idle and the fan never had to kick in, even with the air dam broken. But then, the air dam should have no effect on idle temperatures, right? The air dam was broken when the car was purchased. Never had the overheating problem for the first 14 years of ownership even with the broken air dam. At idle flow is observed through the radiator.

Hi-way; 65mph
Temperature is maintained between 180 -200 on cool days. 200-220 on hot days.
During the 14 years prior to this overheating problem, the temperature was well regulated at 195 in all conditions; idle, stop and go, hi-way, and up-hill, even with the broken air dam.

Stop and go:
Temperature goes to 240 with-in 15 sec of stopping. (fan kicks in)
Drops to 220 at go.
During the 14 years prior to this overheating problem, the temperature was well regulated at 195 in all conditions; idle, stop and go, hi-way, and up-hill, even with the broken air dam.

Hi-way, Up-hill 65mph: (watch out)
Rapid temperature increase to 260+, gage pegged on hot day, 240-260 on cool day.
Water is heard boiling in radiator and can be seen boiling in coolant recovery tank.
Water still boiling 1 hour after shut down.
During the 14 years prior to this overheating problem, the temperature was well regulated at 195 in all conditions; idle, stop and go, hi-way, and up-hill, even with the broken air dam.

As there would be no difference in air flow between hi-way (level) and hi-way up-hill, (both 65 mph) we can assume that this overheating is not an air flow issue, right? Even with the broken air dam? During the 14 years prior to this overheating problem, the temperature was well regulated at 195 in all conditions; idle, stop and go, hi-way, and up-hill, even with the broken air dam.

Therefore the engine is making the excess heat as evidenced by excessive under-hood temperatures. (components too hot to touch such as oil dipstick). This also caused cat meltdown. (cat melt down was more probably caused by excessive rich mixture, which was the cause of repeated emission test failures).

Done so far:
Radiator replacement (3 times) including hoses
Thermostat replacement (10 times)
Water pump replacement (4 times)
Coolant fan switch replacement (3 times)
Coolant fan replacement (3 times) including fan shroud
Carburetor rebuild (5 times)
Carburetor replacement (4 times)
Engine replacement with remanufactured
EFE valve checked functional
EGR valve checked functional
Tuning, timing and carb adjustment done by ASE mechanic.
They can’t figure it out either!
The problem continues

What else is there?

I am not interested in the band-aid fix (putting in a lower temperature thermostat or lower temperature fan switch). I want to find and eliminate the cause!

Thanks

xX89RSXx

iTrader: (1)

After replacing the cooling components, did you make sure air was removed from the system?

BlackBird71

Having drained, flushed and refiled the system at least a dozon times trying to get to the bottom of this problem, I dont' think that air in the system would have been the fault that many times. Plus, I would assume that the engine shop that put in the new engine would have purged any air in the system. With that said, how would I know if there was air in the system and what is the sure-fire method to remove it.

Also, I forgot to mention in my original post that I had replaced the rad cap at least 5 times.

irock88

some great threads on water pumps reverse flow, impeller , and high flow as well there is a thread where someone drilled three holes on their thermostat and that solved their over heating issues. Try the search area on these threads some very good info.

xX89RSXx

iTrader: (1)

The air would cause steam pockets and improper flow of the system. No real SURE way of telling that it has air definately I think. To get rid of it, if it's there......wait till it is cool and start the car after removing the radiator cap. If there is air, then when it starts to warm up, you will see it "burp", in other words you will see bubbles. Don't run too long as coolant expands with heat and will spill. Just keep a close eye on it, you'll be fine.

y84pauloflondon

1. It could be the water pump....without knowing it you could be replacing it with the wrong flow impeller.

2. "OUT OF THE BOX THINKING"!!!!! could a hot tranny cause the coolant in rad to get hot and boil???? Keep in mind tranny temp runs 180*-200*, but 180* is nice. Could a bad tranny or one that is on its way out, send Hot tranny fluid to the rad!!!!

3. HATE TO ASK...... is your fan(s) spinning in the right direction???

4. Engine oil flow, could the oil pump be bad?

5. I'm sure with the rebuild, you(they) made sure that the new gasket aren't blocking any coolant passages?!?!?

RED86Z28

How did it run 195 for all those years when the fan switch was set for 230 the whole time?

Rising temp under load could be a lean mixture or incorrect timing.

Blown84Bird

I've heard of cars over heating from a trany getting hot. Freeway over heating can be caused by the lower Rad hose being sucked shut new hose or not. Was the replacement motor done by a shop? And did it over heat before you replaced the motor?

RED86Z28

Are you using the factory temp gauge?

naf

iTrader: (7)

An out of tune motor will quickly generate too much heat, especially if it's running rich or out of time. All of that fuel still burns and generates heat but it's not all contributing towards generating downward thrust on the piston. Your symptoms are classic for a motor that is out of tune, especially the rapid temp increase under load and the clogged cat.

Did you replace the 305 with another 305 or go to a 350? A 350 with a 305 KS will pull timing.

Have you verified that the ECM is going into feedback mode once it's warmed up?

I'd verify timing is set correctly and is advancing properly (about 22 or so at idle with EST connected).

built91Z28

Thats what I'm wondering. I've never heard of a car that does not need a fan at all to stay cool.

Auggie

Well when you said that it heats up faster going up hill which would put a greater load on the engine (cyl pressure increase) which would lead me to think that you have a blown head gasket.

Auggie

Gregzz4

When it first started to act up, what were the exact symptoms?
Not what parts you changed, but what was it doing?
Then tell me what parts you changed.

Gregzz4

I'm not so sure I can help you with this thread.
After re-reading it, I can see you have a whole lot of detail, but you don't specify when you actually installed parts.
When you say it started to run above factory specs, is that when you installed a new rad, or a new stat or a new pump, or pulled the AC Condensor, or what?

I am not saying you don't have a hard to fix problem, but you are making it hard to trace when you don't give info stating when you changed what parts.

When your problem started, what was happening? Then what did you do? Then what happened?
The list you gave doesn't help, it just tells us you tried everything.

serpentracer

use a infrared temp gauge and check the neck of the thermostat housing.
I bet your temp gauge is wrong. there's no way your engine can over heat if the thermostat is open and coolant is flowing.

and you said the cat melted, that's a lean condition. exhaust components can become red hot and pistons can melt. too rich will cool the engine and exhaust

built91Z28

An engine can overheat even if the thermostat is open. If the air/fuel isnt right. Also running extremely rich or having the timing very retarded will lead to a glowing exhaust. The fuel isnt completely burning in the cylinder and is still burning in the exhaust.

naf

iTrader: (7)

Lean conditions can cause overheating but you'll certainly notice the problem in driveability (pinging/surging) before you notice the over temps. Rich conditions and/or retarded timing don't always cause driveability issues other than loss of power-which may not be noticed at part throttle openings.

bcmag

did this all start after engine relacement?

BlackBird71

No,
all replacement parts, including the engine were an attempt to solve the overheating problem.

BlackBird71

The replacement engine was a remanufactured crate engine (long block), installed by an engine specialty shop. That would include a new oil pump, right? Not sure how trany tempetures would be a factor since there is no trany cooler, it a manual. All replacment parts (including the engine) were an attempt to solve the overheating problem.

I'm reviewing this now because I just started it up yesterday for the first time in 3 years, still overheating.

BlackBird71

The engine never got hot enough (as it shouldn't according to other posts) to trigger the fan.

All tuning/timing, mixture adjustments are set to spec by ASE shops more than a dozen times.

I'm reviewing this now because I just started it up yesterday for the first time in 3 years, still overheating.

BlackBird71

The replacement engine was a remanufactured crate engine (long block), installed by an engine specialty shop. Not sure how trany tempetures would be a factor since there is no trany cooler, it’s a manual. All replacment parts (including the engine) were an attempt to solve the overheating problem. All hoses were replaced with the radiator.

All tuning, timing and mixture adjustments have been set to spec by ASE shops at least a dozen times.

I'm reviewing this now because I just started it up yesterday for the first time in 3 years, still overheating.

BlackBird71

the in dash temperature gauge is frightingly accurate. Spec for fan ON is 238. When the gauge hits 238 the fan kicks on.
The spec for fan OFF is 224. when the gauge drops to 224 the fan goes off. You could set your watch by it.

I'm reviewing this now because I just started it up yesterday for the first time in 3 years, still overheating.

BlackBird71

The replacement engine was a remanufactured crate engine (305 long block), installed by an engine specialty shop. All replacment parts (including the engine) were an attempt to solve the overheating problem. ECM has been replace twice.
All tuning, timing and mixture adjustments have been set to spec by ASE shops at least a dozen times.

I'm reviewing this now because I just started it up yesterday for the first time in 3 years, still overheating.

BlackBird71

The replacement engine was a remanufactured crate engine (305 long block), installed by an engine specialty shop. All replacment parts (including the engine) were an attempt to solve the overheating problem. ECM has been replace twice.
All tuning, timing and mixture adjustments have been set to spec by ASE shops at least a dozen times.
The in dash temperature gauge is frightingly accurate. Spec for fan ON is 238. When the gauge hits 238 the fan kicks on.
The spec for fan OFF is 224. when the gauge drops to 224 the fan goes off. You could set your watch by it.

I'm reviewing this now because I just started it up yesterday for the first time in 3 years, still overheating.

BlackBird71

The replacement engine was a remanufactured crate engine (305 long block), installed by an engine specialty shop. All replacment parts (including the engine) and removal of the AC condensor were an attempt to solve the overheating problem. ECM has been replace twice.
All tuning, timing and mixture adjustments have been set to spec by ASE shops at least a dozen times.
The in dash temperature gauge is frightingly accurate. Spec for fan ON is 238. When the gauge hits 238 the fan kicks on.
The spec for fan OFF is 224. when the gauge drops to 224 the fan goes off. You could set your watch by it.

I'm reviewing this now because I just started it up yesterday for the first time in 3 years, still overheating.

BlackBird71

I've been thinking about that, and I am starting that research.

I'm reviewing this now because I just started it up yesterday for the first time in 3 years, still overheating.

BlackBird71

New engine was no different than the old engine for overheating.

92dream25th

Sorry to interrupt someone else's thread? But could i get some input on my coolant thread? I live in my car and I'm desperate for ideas, plus there is only so much time i can sit at burger kings using their WiFi before they run me off.

naf

iTrader: (7)

Very accurate description of a cooling system that is working perfectly. How is this motor 'overheating'?

BlackBird71

You tell me
Some system or component that I know not of, is causing the engine to inherently run hot. ECM or emmissions related, perhaps?

With much of the under-hood wiring fried to a crisp from extream under hood temperatures, could a fault in that harness cause overheating from ,say, lack of feed back to, or lack of control from the ECM?

naf

iTrader: (7)

Your description of the problem doesn't match the definition of overheating. The motor should be able to sit all day running with the temp rising to the 'fan on' temp, the fan starting up, the temp lowering to the 'fan off' temp, then the fan shutting down. It should repeat this process endlessly until you shut it down or it runs out of fuel. Does this accurately describe its behavior or have I missed something?

The factory temp set points may be a little higher than you're comfortable with but unless it's boiling over it's not overheating.

BlackBird71

Temperature will eventually go to red line. Coolant is heard boiling in the radiator and observed boiling in the recovery tank. Boiling continues for up to 1 hour after shut down indicating extream engine temperature. This was the case with both engines.
I probably ruined the new engine the first time out when it red-lined. I was hoping that the new engine would solve the problem once and for all. I was wrong. 4 grand shot to hell.

naf

iTrader: (7)

OK. So sometimes the system will cool down the motor and sometimes it won't.

I'd look at the timing and tune, especially when you mention failed smog and bad cat.

Are you using the ccc-qjet on the new motor and has the dwell on it been adjusted properly? Timing set to 0-4 degrees advanced with the ESC disconnected?

Your old LG4 would not have maintained a steady state temp of 195 at idle though. It, too, would increase in temp to fan turn on and cycle endlessly.

BlackBird71

All timing, tuning, mixture, carb adjustments have been done by various shops at least a dozen times, They can't figure it out either.

Had 8 different qjets on both engines including Holly rebuilds as well as performance shop rebuilds. all made no difference.

even a 5 minute trip in stop and go on a hot day will result in overheat, with coolant observed boiling.

ChargerBill

Check the overflow tank, if there's a leak or clog the radiator may evacuate coolant with no way of reclaiming it. Food for thought.

Caveman305

iTrader: (8)

either pump not flowing in the right direction
radiator cap is bad(these can be bad off the shelf)
or crack/leak in overflow tank like Chargerbill states


these are the only things that remotely make sense with all brand new parts and your tune is suppose to be right

gregl316

iTrader: (1)

Mine is doing the same thing. I have done the same. I did find the air dam was missing. I have one on order from eBay so lets hope that does it.

BlackBird71

Where did you order the air dam from and how much $$$
its worth a shot

gregl316

iTrader: (1)

off a place on ebay that is in my home state of oregon. it was 75 bucks. i am expecting it tomorrow.

oh and if you don't have one like i don't the damn thing won't cool right. Or so they say.

gregl316

iTrader: (1)

Yes it worked.

crystal383

I have an infrared thermometer I'm using because my water temp gauge broke. I ran my car today and the water neck read 160 which is fine. But my temp sending unit read 230. The sending unit is right in the passenger side head kinda by the header.

Should I be concerned about the temperature on the sending unit? Or is that to be expected because it's next to the exhaust?

naf

iTrader: (7)

Don't assume that the temperature indicator in the dash is, in any way, an accurate indicator of the actual state of nature at the end of the sensor.

crystal383

Well my temp gauge on the dash reads 0*. Doesn't even register. So it's obviously not right. But I go in the engine bay and point the infrared gun at where the water temp sensor plugs into the head. And that is what is reading 230*. If I point it directly at the head it reads 200*. But the temp sensor plug in on the head is right next to a header primary.

With it being next to the exhaust, is that why the reading is so high?

biglano

I am having issues very similar to these. I converted my 89 to a carbureted system, it worked fine. I removed the OBC. I changed the motor to a 350. The air dam is in tact, I had to wire the fans both on all the time to have any chance of cooling. I have changed the water pump 3 times, radiator is brand new, all new hoses, I drive to work - less than 4 miles, by the time I get there, it is @220 plus. sitting in any traffic it runs above 230. I put in a mechanical temp gauge, for fear the dash one was off. I have checked and rechecked the timing. Is it possible to have a blown head gasket and not lose water, or get water in the oil? Head gaskets are about the only thing I have not tried.

FormulasOnly

This is a long shot but it happened to my dad. Similar demon chasing on a Ford F-250 and it turned out that water was flowing too fast through the heater core. Stock from the factory there was a restrictor in the inlet side of the heater core to slow it down. Aftermarket didn't have it. Got the factory hose with the restrictor and problem disappeared.
Any chance your heater control valve has gone bad and letting water move too quick without having the chance to cool? Not to mention bypassing the radiator..