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Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?
Coolant not circulating
Followed shoebox's instructions. When I fill up the radiator with coolant, only the bleeder next to the thermostat will have coolant come out. The bleeder valve on the heater hose will not.
I filled it up all the way and started up the car and scanned with Scan9495 (datalog attached below).
The radiator level will not go down/circulate but will just bubble over with the cap off. Coolant temp was showing 187 degree by the scanner.
I turned it off since the thermostat should kick in at 180 and I didn't want to damage anything but maybe I turned it off too early?
As a recap:
- New ACDelco Water pump
- New Thermostat by previous owner (But I need to verify this)
- New heater hose check valve. It is going the right direction
- New heater core
- BOTH upper and lower radiator hoses are hot to the touch
- BOTH Heater In/Out hoses are not warm or hot at all. It appears it is not getting coolant there since no coolant will come out of the bleeder valve either.
There seems to be a problem with circulation to the heater hoses or circulation in general. I removed the thermostat and am going to test it in a pot of water on the stove today.
Haven't run past 187 degrees so I haven't been able to troubleshoot fans yet. I am unable to bleed air fully because it appears coolant is not reaching to the second bleeder valve.
Injuneer, I attached my datalog if it'll help anything.
Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?
Originally Posted by Injuneer
What do you mean by “the thermostat should kick in at 180”? 180°F is when the thermostat starts to open. Won’t be fully open until about 200°F.
I'll download the data log when I have access to my laptop in the morning.
I see, so it looks like I turned off the car prematurely.
But seeing as how I hit 188 degrees, shouldn't the coolant level have started to drop and start to circulate at least a little bit visually in the radiator fill neck?
I think it is circulating seeing as how both upper/lower hoses radiator hoses were hot. Maybe not fully. Also the heater core is new I replaced it because the previous owner said it had no heat so I figured I might as well address it. The actual heater core hoses are both cold.
Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?
Yep, it's the correct thermostat but just wanted to update.
UPDATE: The car is now bled completely properly, no leaks either. Idled for 40 minutes to test the temps and fans.
The cooling fans come on at 226 deg according to the scanner. According to the gauge cluster, this is the line at 3/4 to max.
Once the cooling fan comes on at 226 deg, the gauge cluster lowers to a point a little past the 1/2 mark.
So, it doesn't seem like the car is overheating because the cooling fans bring it back down but it seems like its hovering around 210+ at idle, that seems high?
It does bother me that the gauge is playing around above the 1/2 mark at its lowest, and goes up to 3/4 and keeps fluctuating.
Is that normal operation? Most cars I've owned the temp gauge gets to operating temp and just stays right near the middle or slightly below.
I've tested the temp sensor in the cylinder head and it wasn't too far off from the water pump temp sensor so I don't think it's running much higher.
If this is normal, then I will just drive it. But I'm concerned that the gauge is moving around in the upper half of the temperature range.
As for the ABS, I was able to use scan9495 to activate the abs block and bleed it.
Injuneer, if you get a chance could you take a look at the datalog I took of my temps? (I attached the file, as well as a screenshot of the charts)
Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?
That temperature is typical of a normal LT1. Once you are driving it you’ll notice that the temp stays a good bit cooler than what it idles at. These cars idle hot.
Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?
Originally Posted by 97rebuiltZ28
That temperature is typical of a normal LT1. Once you are driving it you’ll notice that the temp stays a good bit cooler than what it idles at. These cars idle hot.
Oh interesting, I didn't know that. Ok great so I guess no problem here thanks
Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?
Got to allow me time. I just spent quite a bit of time looking at the first log this afternoon (Monday), and writing down notes so I could post the results tomorrow (Tuesday) when I am on my laptop with a real keyboard. Long posts are not a lot of fun from the IPad I use most of the time.
Quick summary on the first log - the start, warmup and idle are textbook. Good example of exactly what you should expect to see for that phase of engine operation.
I'll do my best to find some time Tuesday to look at the coolant temps, but doesn’t seem abnormal. GM designed the engine to operate at 210°F. That's why they set that temp in the middle of the gauge. It produces low emissions and good MPG. Does not necessarily produce optimum power. That's why many people switch to the 160°F thermostat, and reprogram the fan on/off temperatures.
You may still have air in the cooling system. That could make the sensor in the head report erratic (but real) temps. Does the engine still have the steam pipe removing coolant (along with air and steam) from the back of the heads?
Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?
Originally Posted by Injuneer
Got to allow me time. I just spent quite a bit of time looking at the first log this afternoon (Monday), and writing down notes so I could post the results tomorrow (Tuesday) when I am on my laptop with a real keyboard. Long posts are not a lot of fun from the IPad I use most of the time.
Quick summary on the first log - the start, warmup and idle are textbook. Good example of exactly what you should expect to see for that phase of engine operation.
I'll do my best to find some time Tuesday to look at the coolant temps, but doesn’t seem abnormal. GM designed the engine to operate at 210°F. That's why they set that temp in the middle of the gauge. It produces low emissions and good MPG. Does not necessarily produce optimum power. That's why many people switch to the 160°F thermostat, and reprogram the fan on/off temperatures.
You may still have air in the cooling system. That could make the sensor in the head report erratic (but real) temps. Does the engine still have the steam pipe removing coolant (along with air and steam) from the back of the heads?
No worries, take your time thanks for the help.
I still have the steam pipe connected. I had a leak on one of the banjo bolts and fixed it before I bled the coolant. During the bleeding process there was a steady stream of coolant coming from the steam pipes I think given that the idle is known to hover over 210 deg and the fans work, it shouldn't be a problem.
But I do plan on tuning the fans to come on at 200 for lo and 210 for high
Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?
Took the car for a test drive. As far as all things mechanical go, seems to be running great. Clutch, driveshaft, engine, etc.
One thing I noticed is somewhere on the top of the engine makes a ticking/clacking noise.. sounds like it's coming from maybe in the intake manifold area but not 100% sure.
From what I read, people say the LT1s have loud lifters. I haven't owned an LT1 long enough to know if it's normal. Might be the alternator pulley also.. kind of hard to tell. I'm going to spray some soap water on the pulley to see if the noise goes away.
However, I noticed an oil burning smell and when I came back I saw a few drops of oil on the floor. Looked up with a light and one of the timing cover seals are leaking. I'm betting my money it's the water pump seal. The opti drive seal was super easy to put on, the front main seems ok. But the water pump seal with that paper ... I used a socket and thought I did it right but maybe I stretched it out a bit too much.
Either way, I'm going to wait until it's bright to take another look and if the leak isn't bad, I'm just going to drive it for a while until I can get to it cause it looks like you gotta remove the crank, opti and water pump just to get to the damn seal. I thought you can get to it behind the water pump but apparently it's hiding behind the opti.
Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?
If you need to replace the WP drive seal the WP, Opti and damper (not hub) need to come off. Can be tricky to install without folding over the inside lip of the seal. There is a tool you can buy for around $20 (pic) on ebay or make one from a Sharpie pen cap. IMHO just buy the tool. That seal installs dry, no oil. It is a PTFE seal
Re: Looking to buy a 94 Z28 with head gasket problem, what to look for?
Originally Posted by Chimera96
If you need to replace the WP drive seal the WP, Opti and damper (not hub) need to come off. Can be tricky to install without folding over the inside lip of the seal. There is a tool you can buy for around $20 (pic) on ebay or make one from a Sharpie pen cap. IMHO just buy the tool. That seal installs dry, no oil. It is a PTFE seal
Awesome I thought I had to remove the hub and press it back on. Damper only is much easier.
I saw a video of someone using a 1/2 socket. I was able to get it in but my socket has a little notch it in and the black rubber kind of got caught. I was able to bend it back but I guess it for stretched out. I'm going to buy that tool thanks for the link
