Engine temp in 67 Cadillac 429 engine

[richardbergquist]

My temp gauge often stays a tad below 1/4. Sometimes, like today, on a highway with some hills it goes up to almost 1/2. How does your 429 temp gauge act?

[JohnnyRockit]

I don't have a 429, but when I had a 472 and it acted like that it was low on coolant. Just fine around town, but significantly warmer at highway speeds.

[The Tassie Devil(le)]

I always tend to be on the side of not really believing the factory gauges, as they are only a guide for the basic driver.

What I like to do is to temporarily fit proper gauges and look at both the gauges, factory and the accessory, and see what each is reading.   Then, once satisfied that the operation of the factory one is good, then remove the accessory one.

I did that to check the oil pressure when I purchased my '72 and now just use the idiot light.

Bruce.

[bcroe]

I want to know the temp, so I use the small, 270 degree gas tube gauges.  It
generally stays right at the thermostat rating.  If the gauge starts wondering
around, I take that to indicate a radiator overhaul is needed.  If that doesn't
do it there may be a fault such as cracked head or bad head gasket. 

Bruce Roe

[TJ Hopland]

Pick up one of those IR temp gun things.  They are cheap now days and even the cheap ones appear to be reasonably accurate.   Point it at the thermostat housing and where ever the temp sender is to see what the actual temp is vs what your gauge reads.  That may give you an idea if your gauge is at at least consistently reflecting the actual coolant temp.

67 is into the emissions era so that would for sure be an engine that should be hanging right around 200*F all the time.

IF you have never had one before they can also be a few hours worth of entertainment pointing it at things and playing with pets using the laser.  You can find out if your pets temp goes up after they chase the thing for an hour.   

[Scot Minesinger]

I installed a real good Autometer gauge on my 1970 Cadillac with 472 engine.  During weather below 70'F it generally runs at thermostat setting.  When it is sunny and in the 90's in idling traffic, it might creep up to 208'F or so.  It does run around 200'F on sustained highway trips. 

The 429 usually operates at around 1/4 on temperature gauge and usually does not go past 1/2.  Highway travel is usually not to taxing on cooling systems, 1/2 seems a little high.  What make the temperature climb on highway trips where significant running speeds and sustained higher fuel use (idling at stop sign is 0.0 mpg, but fuel per hour is low) is a clogged exhaust.  Unfortunately it is a little difficult to tell because the exhaust pipe may looks fine on outside (no rust - still aluminized finish), but rusted to the point of blockage on inside.  This happened to me on a 1972 Eldorado, ran fine around town, overheated on highway.  Plus the let it run with vacuum gauge and watch it decline to diagnose it was not too conclusive.  Had to just go for it and trust my gut, and then I cut the exhaust pipe and at the resonator it was 70% blocked. 

This probably would not happen with an original exhaust (long resonator), but it seems certain to happen on a replacement exhaust.

[savemy67]

Hello Richard,

My '67 429's temp gauge usually hangs around the 1/4 hash mark.  There is some variability, but as I have not driven my car on an extended trip (100 plus miles), I don't know what my gauge will read when the engine stays warm for a long period of time.

Installing a mechanical gauge is a good way to keep an eye on how your cooling system is functioning.  A good gauge will give its reading in degrees, so you can compare the reading to specifications like the thermostat setting.  You can also use the gauge to roughly calibrate the stock gauge.

If you are satisfied that your cooling system is in good shape (no leaks, correct radiator cap, good water pump and belts, proper coolant mix, etc.), I would not be too concerned about a rise in the gauge with the car going uphill.  Moving the car uphill requires more energy.  This is provided in the form of more fuel being burned in the combustion chamber.  The increase in heat energy being imparted into the iron of the cylinder head (note the location of the coolant sensor) at higher RPMs is a little greater than is the ability of the cooling system to carry away that heat energy.

Respectfully submitted,

Christopher Winter

[bcroe]

I installed a real good Autometer gauge on my 1970 Cadillac with 472 engine.  During weather below 70'F it generally runs at thermostat setting.  When it is sunny and in the 90's in idling traffic, it might creep up to 208'F or so.  It does run around 200'F on sustained highway trips. 

What make the temperature climb on highway trips where significant running speeds and sustained higher fuel use (idling at stop sign is 0.0 mpg, but fuel per hour is low) is a clogged exhaust.  Unfortunately it is a little difficult to tell because the exhaust pipe may looks fine on outside (no rust - still aluminized finish), but rusted to the point of blockage on inside.  This happened to me on a 1972 Eldorado

I cut the exhaust pipe and at the resonator it was 70% blocked. 

I like Autometer, drove by their plant yesterday.  I picked up a cheap exhaust
back pressure gauge some time ago, just drill a small hole and insert a probe. 
They also supplied some plugs for the hole.  I weld a couple bungs on my
(stainless) systems for this and WB OX sensors.  Bruce Roe

[Eric DeVirgilis CLC# 8621]

A tick above 1/4 is what I've observed with almost every temp gauge in Cadillacs I've had from 59-64 under most conditions. On very hot days, especially if climbing a long grade it may reach the halfway mark but rarely.

["Cadillac Kid" Greg Surfas 15364]

A mal functioning or incorrect vacuum advance canister is a good way to add 10 to 30
Degrees on the highway
Greg Surfas

[richardbergquist]

Thank you for all valuable replies. I feel I probably don't have to worry too much about the gauge moving from 1/4 to 1/2 in warm weather. Lately, when it's not been in the 100s in South Texas, the gauge has not moved to 1/2.