34oSc

Well, here goes....
Had one of my boys take me up to pick up the car. Drove it about 5mi towards home and it started getting hot- dig about 213 and ana @260.
I shut her down and we towed it home, only intermittently running the engine to use the brakes or power steering.
Funny thing was, it didn't seem to want to get hot as quick when I got it home...I let it run until it started blowing cold instead of hot air out of the heater vent. When it got to the 213/260 point it stops blowing hot air and goes to cold. I let it sit till tonite.
Tonite the temp is about 40 here(F)...
Start it up @5:09pm
Dig says 51, ana hasn't moved
5:18pm Dig= 163, ana @185 hashmark, blowing warm(NOT real warm)
5:22pm dig=186,ana @ 1st hashmark above 185, blowing warm
5:27pm dig=211,ana @ 2nd hashmark above 185, blowing HOT(NICE!)
5:30pm dig=205,ana@ 260, blowing cold.
I shut her down and could hear bubbling shoving hot outofthe upper tank and into the lower res. This stopped after2-3 min.
I shut her down and there she sets. It IS much better than it was- spitting and spewing with the cap off and boiling like mad...but better isn't all that great...
I DID see that the driver's side fan was on, never did see the pass side one come on....further instructions???? TIA

No Go

Are your filling the coolant tank and overflow each time the car cools off?

This pattern still exhibits air in the system...especially the heater core going cold...ie no coolant left in it so no hot air.

theadmiral94

ELVIS' C4,

Your idea of using the shop-vac as a blower is a great idea.

I've used that trick on my sailboat diesel engine to assure the coolant hoses which run many feet to the hot-water heater are clear -- it as amazing how much junk got hung-up in the hoses and hot-water heater -- so it should work equally good on our engines.

And, given the LT1 coolant vapor pipes which attach to the rear of the heads, by blowing the air into pressure tank, and with the thermostat removed, it could move lots of junk to the radiator lower hose and thereby the radiator drain.

theadmiral94

34oSc,

I presume the test info "blowing warm,,, hot,,, cold" means inside the car --

BTW, digital temps below 240 F is NOT considered overheating.

When you were doing the timing/temp tests, since the digital temps never reached fan-on temps (228 F), I presume your comment about "did see driver side fan" was not during these tests -- or you had the A/C turned-on. Please clarify...

You might have two different problems and whereas the heater being cold could contribute to engine temps, they could be otherwise unrelated and might suggest using the heater to diagnose the engine temps might provide inaccure information.

The temp difference between the digital and analog gauges implies a blockage/failure of the coolant to flow through the engine back of the engine. This could be caused by: bad/wrong thermostat, loss of pressure via a bad/weak radiator cap, clogged coolant-vapor pipes, or a blown head gasket.

The blowing 'cold' also means coolant has stopped flowing through the heater-core.

That could be due to a bad water-pump, or heater hose valve, or vacume which might control the heater hose valve.

If I recall correctly, the lower/input heater hose runs from the water pump through a plastic flow restrictor, through a shut-off valve, to the heater-core input, and then runs from the heater-core output to the pressure tank.

So, cold temps inside the passenger compartment could imply a bad or weak shut-off valve, a bad water-pump or maybe a bad/incorrect thermostat.

Recommend feeling the two heater hoses going to the heater-core -- are they both the same temps or is one cold? If one is cold, it implies either the heater-core is blocked or the shut-off valve or flow restrictor is deffective.

LT1CORVETTE

1996 LT1
Does the bleed screw under the throttle body look similar to the one on top of the water pump? I have been looking, but I can't seem to find it.

34oSc

PROBLEM SOLVED!!!!!
Just parked it and waited for warm weather...
Took it to a buddy that works on cars and told him it was suspected of having a blown head gasket...(chevy dealer suspeced it was blown)

He played with it for a day or two off and on- was suspect of the radiator, water pump, heater core, thermostat...
He was starting to take it down and he discovered...
Turns out it was a bad shaft connector from the camshaft to the waterpump!
It would turn the pump at idle, but speeding the motor up would cause the connector to spin(slip).
I changed to oil- the old had been hot, she's back on the road and my mills runnin' fine!

onedef92

I use a Shop Vac to evacuate all the coolant out of my cars, too. Gets the heater core and block areas around the knock sensors, too.

66IISS

Does the thermostat need to be removed in order to use this method? I'm assuming you're using the shop vac at the coolant fill resivoir, by the ac evap box? I need to drain my coolant this weekend and I'd rather not worry about removing the knock sensors. I'm also not worried about crud because the engine has run for 10 minutes since being rebuilt.

skybolt31

I know I haven't gotten enough sleep lately, but what does "changed to oil" mean? I assume there is a typo in there somewhere......

34oSc

Nice catch, Skybolt! Maybe it was ME that hadn't had enough sleep!
I changed THE oil...cut me some slack, I used to fly an ultralight LOL.

onedef92

I've never removed my thermostat but it's probably best too, since the procedure won't work unless the engine is warmed enough to open the device.

After you've removed the thermostat (much easier than removing the knock sensors) put the vacuum hose over the opening at the coolant fill reservoir and use the blower outlet on your vacuum to force all the liquid out of your system. It shouldn't take more than 30 to 40 seconds. Just hold it in place until nothing but air comes out the petcock.

BucfanTitan

I know this is an older post but I hope the members with the vacuum idea are still around.

If I do use the vacuum and place my hose at the bottom fill reservoir I will be able to have enough flow/force to push out the entire system. Are people still doing this trick? Has it turned out to be a good idea?

then fill with distilled water let the engine warm up. Cool down drain repeat until clear. Add 50/50 coolant mix, bleed and good to go. that seems to be a good idea to me....

Tom400CFI

Man....^That is way too much work. You don't need a vacuum, you don't need distilled water. Don't need to fill it and run it and do that over and over.

*Remove both side block drains (one is a NPT plug, other is a knock sensor)
*Remove radiator hoses from one side, each.
*Remove heater core hose from water pump.
*Stick garden hose and run water through radiator hose (to flush radiator) until water runs clean -should be just a few seconds.
*Stick garden hose on disconnected heatercore hose and run until water running of of engine block drains runs clean (about 1 min). *This flushes your heater core, heads, intake (on older engines, not the LT1), and block.

*Put plugs back in after water drains out, hook hoses back up.

*Open bleeders and fill. When coolant starts to come from bleeders w/no air, close. Top off, you're done.

brotheomen

What worked great for me was to drain radiator, remove hose with heater core resrictor, remove thermostat housing, replace petcock, fill engine at waterpump, you will hear gurgling, thats the air burpin out. Then assemble thermostat and housing, replace hose to pump with restrictor, fill the rad crack the bleader and coolant in rad will drop, then fill rad more. Put cap on put air intake on with all the periferal asosiated plugs and start er up. Let it get to temp and crack the bleader again on the thermostat housing untill you see coolant. Done. The real till here was filling at the thermostat housing. Runs great!

A Peter C4

1996 does not have throttle body bleed screw or coolant fed to throttle body like 1994 and earlier LT1s.

Tom400CFI

People sure like to make stuff unnecessarily complicated. Here's all you really need to do:
EDIT: Oh yeah...Runs great!