Engine temp weirdness

[Buzz Skyline]

My engine temperature gauge is telling me strange stuff.

When I first start my car, the needle climbs until it's in the red and the car appears to be overheating. If I then turn off the car and wait a few minutes before starting it again, the needle is very high, but after a minute or two rapidly falls to the normal operating range. As long as I don't let the car cool all the way down, everything is fine. If it sits long enough to get cold, the whole process starts again.

Any idea what this is? Could the thermostat be sticking? I'm used to them just failing outright?

[METAL C6R]

From what you're describing, I am under the same assumption. "Sticky T-stat".
This kind of thing happens to my 1984 Monte Carlo ( occasionally & not as bad ). It heats up quite a bit on start up/ first hundred yards of driving, but then it shoots back down. It hasn't gotten so hot where it's worried me to shut the car down though. just enough to notice it and have it on my to do list.

[STiPWRD]

It could be that you have air in your coolant system. This would cause hot vapor to collect where the engine temp sensor is located in the upper coolant cross over pipe. Do you have coolant in your overflow tank?

[68GT500MAN]

I would think that STiPWRD has the right idea.

[904svo]

This is a known problem, the engine has to be burp. Don't let it overheat as it will blow your head gaskets if let to run too long.

[Buzz Skyline]

It could be that you have air in your coolant system. This would cause hot vapor to collect where the engine temp sensor is located in the upper coolant cross over pipe. Do you have coolant in your overflow tank?

Yep it all looks normal, with the same amount of fluid in the overflow tank as usual. I have Wayne's coolant system mod too. The thing is, I've been driving it quite a while and the problem just began on Labor Day, so something has to have changed. That means the thermostat is going bad, or the water pump is wearing out, or there's a clog/kink in a coolant hose, or something else I haven't thought of.

[Buzz Skyline]

I replaced the thermostat last night, the water pump isn't leaking, and I checked to make sure the coolant system is full, so if it still has the problem today that leaves hose problems or the "something else that I haven't thought of yet."

[Buzz Skyline]

I think I've found the problem. I believe the thermostat isn't warming up enough to open because when I installed my AWIC the intercooler piping pinched the hose going to the heater core circuit. This should only be a problem on 2002-2003 motors with the non-clocked turbo and an AWIC. Newer motors route the heater circuit differently and there isn't any interference.

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Now I either have to clock my turbo or find some way to take the pressure off the hose.

[STiPWRD]

You could also replace your upper coolant cross-over pipe to 04-07, that's what I did. In fact, I might have an extra one of these pipes.
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You'd have to remove your intake manifold to do this.

[Buzz Skyline]

Interesting suggestion.

I will probably go with clocking the turbo though, because it will both fix the interference and shorten the intercooler piping run.

[cmcintyre]

Slightly off subject, but since you have been in this system just recently.... Got an 03 so I have the different routing and am installing a Vintage Air heater. Can't tell from your diagram (where is that from, btw?) or service manual which of the two smaller pipes coming off the water pump is discharge (pressure) to the heater circuit, upper or lower. Any idea? Thanks.

[Samiam1017]

this may be a stupid question but why would clocking the turbo have any effect on this?

[STiPWRD]

this may be a stupid question but why would clocking the turbo have any effect on this?
Clocking the turbo will rotate the output piping coming off the compressor. As is, the piping goes over the top of the trans, under the AWIC, and interferes with the 02-03 coolant heater pipe. Rotating the compressor (or clocking the turbo) re-directs the piping so it no longer interferes with the heater pipes.

Clocking the turbo moves the attachment points for the stock wastegate so you'd have to either fab up a bracket or reweld some different attachment points onto the compressor.

[Buzz Skyline]

. . .you'd have to either fab up a bracket or reweld some different attachment points onto the compressor.

Or buy a bracket from Zero Decibel Motorsports (http://zerodecibelmotorsports.com/products/td04-clocking-bracket/).

[Buzz Skyline]

Slightly off subject, but since you have been in this system just recently.... Got an 03 so I have the different routing and am installing a Vintage Air heater. Can't tell from your diagram (where is that from, btw?) or service manual which of the two smaller pipes coming off the water pump is discharge (pressure) to the heater circuit, upper or lower. Any idea? Thanks.

I got the diagram off of the NASIOC forum. It's not specific to any model, I believe, it's just a general schematic to show conceptually how things work. I'm afraid I have no idea which is the 'in' and which is the 'out' on the engine, but firing it up briefly without any connection to them should make it clear since the pump should be pushing fluid through it even when it's cold.

[STiPWRD]

Or buy a bracket from Zero Decibel Motorsports (http://zerodecibelmotorsports.com/products/td04-clocking-bracket/).

Ahh, didn't know Craig was making these already. I'm not sure it would fit on my 18g either way, but certainly could solve your problem.

[cmcintyre]

I got the diagram off of the NASIOC forum. It's not specific to any model, I believe, it's just a general schematic to show conceptually how things work. I'm afraid I have no idea which is the 'in' and which is the 'out' on the engine, but firing it up briefly without any connection to them should make it clear since the pump should be pushing fluid through it even when it's cold.

Thanks for the diagram, though. Traced pipes on the engine, mine has a slightly different routing for throttle body. Upper on the water pump is pressure, lower is return.

[Samiam1017]

Clocking the turbo will rotate the output piping coming off the compressor. As is, the piping goes over the top of the trans, under the AWIC, and interferes with the 02-03 coolant heater pipe. Rotating the compressor (or clocking the turbo) re-directs the piping so it no longer interferes with the heater pipes.

Clocking the turbo moves the attachment points for the stock wastegate so you'd have to either fab up a bracket or reweld some different attachment points onto the compressor.
I know what clocking the turbo is. I clocked mine.. it had no effect on the coolant flow??

[Buzz Skyline]

I know what clocking the turbo is. I clocked mine.. it had no effect on the coolant flow??

The problem I was having was the AWIC piping pinching the heater core bypass tubing and restricting coolant flow to the back of the thermostat. That led to erratic opening and closing of the thermostat. Clocking the turbo doesn't affect coolant flow, but it will allow me to remove the interference.

As it happens, I was able to move things around enough to stop the tube from getting pinched even without clocking the turbo, but I'm still planning to clock it to clean things up and ensure that the tube doesn't get pinched again.

[Samiam1017]

The problem I was having was the AWIC piping pinching the heater core bypass tubing and restricting coolant flow to the back of the thermostat. That led to erratic opening and closing of the thermostat. Clocking the turbo doesn't affect coolant flow, but it will allow me to remove the interference.

As it happens, I was able to move things around enough to stop the tube from getting pinched even without clocking the turbo, but I'm still planning to clock it to clean things up and ensure that the tube doesn't get pinched again.

thx I understand now