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How hot does yours run?

2K views 17 replies 11 participants last post by  MBGraham 
#1 ·
I'm not sure what the unmarked tic indicates-I'm guessing around 212F. Mine held about a needle above the mark on our recent road trip. Cruising at 75-80 mph at 3700-3900 rpm. Does this temp seem normal? The only adverse effect seemed to be a tendency to die when idling down (vapor lock?)

4.5 liter d-jet.

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#3 ·
I'm not sure what the unmarked tic indicates-I'm guessing around 212F. Mine held about a needle above the mark on our recent road trip. Cruising at 75-80 mph at 3700-3900 rpm. Does this temp seem normal? The only adverse effect seemed to be a tendency to die when idling down (vapor lock?)

4.5 liter d-jet.

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My 72 Djet runs at just slightly over the 175F mark when driving. maybe 185F? If leftv idling for long period, it may creep up.

Your temperature seems high. At one time my car was like that and I ended up having cracked exhaust manifolds :(

High temperature can be due to cooling system problems, but also due to timing setting. A retarded timing setting will cause engine to run hot. You could try setting timing so that it is about 27deg BTDC at 3000rpm. This will mean that it will be at about 5deg BTDC at idle with vacuum. This is easy to do with a timing light and perhaps you will run a bit cooler.
 
#4 ·
Thanks. I did recently set timing to specs (can't remember the numbers but I'll check it).

I also just replaced the aux fan switch which is supposed to come on at 212.

Mind you, this was hours of running on the interstate at high revs. When I got off on the country roads at 55 mph, it ran just above 175.

Ambient air temp was around 80F.


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#7 ·
Thanks. I did recently set timing to specs (can't remember the numbers but I'll check it).
Just to be clear - The numbers I suggested are not the MB specs. The NA specs are designed around emission control. A more advanced setting runs cooler and probably better all round. The euro cars are set that way.
 
#5 ·
Also, last year was a new water pump and I had the radiator cooked out an flow-checked while it was out. I haven't done the citrus flush so maybe some build up in the engine passages?


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#6 ·
Masan68, the temp sound just fine for an 80* day. What other drains on power were happening at the time? AC? That will add a few calories.

If you have owned and cared for the car from new, your plumbing is probably ok. If this car may have seen sub par attention over the past40 years, I would be planning a flush. There could be malign reactions from maybe having green stuff in, and mixing with G-05. I found a huge excess of crud when I put in a fresh water pump and thermostat. Got new hoses, but that may have had no impact on cooling.

The white crusty was so thick, that I had to use air tools and wire wheels to get down to metal. I was scared to think what was in the block. I did the normal drain, tossed in Dawn solution as a flush, moved to a CA solution for about 200 miles, and five water flushes, before filling with Zerex.

This got me a good flowing system, but the vicious fan failed a few years later, and I had to do the flushing again. There was still more goo left in the system that came out of solution, so it can take years to get rid of what took decades to accumulate.
 
#8 ·
I see similar temps in my car. Around town and short runs at freeway speed the gauge sits at bit above 175 but extended runs at 70+ mph I see the temp rise also. My car has the cats under the hood (although they are hollowed out) so I have always assumed that to be the cause. This seems backwards to me I would think in town traffic, sitting at stop lights and such would make the temp rise but even with ac on it stays just above 175, and the constant higher air flow at higher freeway speeds would keep Zthe temp lower.

I am assuming you took that picture with engine off and that is why the oil pressure is at 0, cause that could be a whole other story.
 
#11 ·
Revs are normal at that speed. Temp has more to do with coolant flow and air flow to heat exchangers. With AC off and heat on, you should see a goodly decrease in engine temp at the cluster.

I climb mountain passes at 75mph, and temp does not get above 185 on summer days, normally. When the system was not at its best, I did get much higher showings in the 210-redzone. Driving 75-80 for 250 miles did not make for much heat. Slowing down or climbing 6% grades did not show any effect either with a clean system.

This is for a 73, no AC, kept in good kip. YMMV
 
#12 · (Edited)
These cars have electric gauges. Increased resistance can cause a falsely high reading. The 107 often has increased resistance at the instrument cluster where the gauge itself plugs into the circuit board. Use an infrared temp gun to confirm the temp reading.

One sign of a resistance problem which will be seen sometimes is a needle that is not smoothly operating all the time. Sometimes it will "jerk" and change positions.
 
#15 · (Edited)
I am away from home, but on the net, I see 2865rpm at 100kph (62mph) and also 24.5mph at 1000rpm in top gear. There may be differences in the transmissions and rear end of these cars.

using the 62mph number, the rpm at 75mph would be 3466rpm

using the 24.5mph number, the rpm at 75mph would be 3061rpm

Maybe someone can find the official numbers for the OPs car. This is not official, but from http://www.automobile-catalog.com

 
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