Speedometer reads way too fast

[east302]

Just out of curiosity did you get the ACDelco part number I posted up? I've had issues with Stants and other aftermarket brands in the past but that factory ACDelco thermostat has never given me issues.

Either way, glad it improved at least a little.

That Delco 131-151 is the thermostat I have in my truck (1998, 350). Have never had any issues with it.

The gauge in my truck with that thermostat has never been accurate but the one in my Tahoe is. That's the one that I posted a gauge picture of a couple days ago.

Truck's gauge reads 155 with the upper radiator hose hot. The ECT sensor reports 192 which agrees pretty closely with Delco's thermostat literature claiming a 197 (?) setpoint.

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[Blackwater]

That Delco 131-151 is the thermostat I have in my truck (1998, 350). Have never had any issues with it.

The gauge in my truck with that thermostat has never been accurate but the one in my Tahoe is. That's the one that I posted a gauge picture of a couple days ago.

Truck's gauge reads 155 with the upper radiator hose hot. The ECT sensor reports 192 which agrees pretty closely with Delco's thermostat literature claiming a 197 (?) setpoint.

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so this is a case where there is an inadequate communication from the sensor to the cluster? check wiring to the cluster by checking continuity. shouldn't have any resistance from the sensor to the cluster.

 

[redfishsc]

For folks with temp gauges that read lower than you expect them to at operating temp:

Most likely your sending unit (the one near the driver's side exhaust manifold) is worn out. Next time you do a coolant flush, swap it out. Removing the old one might be a bit dramatic, just don't shank it off. If it's frozen badly, may want to leave well enough alone.

You can verify if it's that sending unit pretty easily. Hook up anything that can read temp from OBD2 port. I use a bluetooth plug linked to my Android, using the Torque Pro app. OBD2 will read temp from the sending unit that sits on top of the intake manifold.

My dash gauge (99 Suburban) always said it's running about 150/160 but I have a 195 Thermostat in it, and the OBD2 app always shows the temp being 190-198.

I have a second 99 Suburban I'm in the middle of pulling the top end of the motor out for a head gasket swap. When I drove it home for the first time the other day, I noticed that the temp read about the same, 160. I'll swap the sending unit on it while I'm doing the head gasket.

 

[Blackwater]

For folks with temp gauges that read lower than you expect them to at operating temp:

Most likely your sending unit (the one near the driver's side exhaust manifold) is worn out. Next time you do a coolant flush, swap it out. Removing the old one might be a bit dramatic, just don't shank it off. If it's frozen badly, may want to leave well enough alone.

You can verify if it's that sending unit pretty easily. Hook up anything that can read temp from OBD2 port. I use a bluetooth plug linked to my Android, using the Torque Pro app. OBD2 will read temp from the sending unit that sits on top of the intake manifold.

My dash gauge (99 Suburban) always said it's running about 150/160 but I have a 195 Thermostat in it, and the OBD2 app always shows the temp being 190-198.

I have a second 99 Suburban I'm in the middle of pulling the top end of the motor out for a head gasket swap. When I drove it home for the first time the other day, I noticed that the temp read about the same, 160. I'll swap the sending unit on it while I'm doing the head gasket.

So what if you changed those out, flushed it and you have a OBD1 port.

 

[redfishsc]

I do not know if OBD1 has a separate sensor for temp.

I should know, I've owned several OBD1 TBI trucks, I just can't remember.

 

[Blackwater]

I do not know if OBD1 has a separate sensor for temp.

I should know, I've owned several OBD1 TBI trucks, I just can't remember.

it does not

 

[AJM008]

I have a simular Speedometer problem. I have hooked up a diagnostic tool to the obdII port and the speed reads accurate, I have a radar sign by my house and it matches what was read on the tool. My speedometer reads roughly 10 MPH high. From reading all the posts above, Should i be looking for a cluster?

 

[Blackwater]

I have a simular Speedometer problem. I have hooked up a diagnostic tool to the obdII port and the speed reads accurate, I have a radar sign by my house and it matches what was read on the tool. My speedometer reads roughly 10 MPH high. From reading all the posts above, Should i be looking for a cluster?

What year is your baby?

 

[east302]

I have a simular Speedometer problem. I have hooked up a diagnostic tool to the obdII port and the speed reads accurate, I have a radar sign by my house and it matches what was read on the tool. My speedometer reads roughly 10 MPH high. From reading all the posts above, Should i be looking for a cluster?

What is the stock tire size on the door jamb label and what size tires are you running? Has the rear axle been changed versus what it came with stock?

For a 1998, GM says that a 4-mph error is within spec.

Speedometer inaccurate:

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[AJM008]

What year is your baby?

98 k1500