DeTomaso Mailing List: September 2000, Message #31

It could be one of two things.

1. Guage problem.  Go to the local auto parts store and buy a mechanical
guage to temporarily stick in the block instead.

2. you put the head gaskets on wrong and water cant flow through the engine.

A warm engine will normally build pressure
A new engine will heat up faster and run a LITTLE wamer.
Higher compression and larger cam will make an engine run hotter.
You could advance the timing a bit more, it will make the engine hot, but
if that is the case, it will also  be making the manifolds glow red.
In a front engine car, a missing bypass plate wont make it overheat that much.
If you had air in the engine, it would not likely build up pressure.

my opinions.

Dave "Had em overheat myself" D

At 12:07 PM 9/1/00 -0400, you wrote:
>Well, I'm at the end of my rope for the moment... I need some more rope.
>
>Yes, the 351C in the new Mach I engine is overheating, according to the
>guage in the dash.
>
>Background:
>The original engine I had rebuilt 15 years ago was build with dished
>pistons, open chamber heads and a mild cam.  The temp gauge ran about
>one-third into the "normal" range.  All was one with the universe.
>
>The new engine is built with flat top pistons, quench heads and a radical
cam.
>I'm running about 10 degrees of initial advance, at idle.  I'm not sure how
>the carb is jetted, I just know it's running (it might be too lean).
>
>When running for less than five minutes, the temp gauge is almost pegged on
>High , past the "normal" operating range.  However, there does not appear
>to be coolant ejecting itself, and when shut off, there are no audible
>indications of bubbles.  The upper radiator hose feels cool.
>
>Okay, so I go down and pick up two things from Napa, another thermostat and
>another temp gauge sending unit.  I go home, I extract both from the
>engine.  I go into the house and using a "non-cooking" pan, I insert both
>thermostats (old and new) into the water and start it boiling.  With a
>thermometer in the water, I find both thermostats begin opening at about
>200 degrees as read on the thermometer.  The 'stats are rated at 195.
>Seems to me they are opening a bit too late.  Anyway... both are the same,
>must be okay.
>
>I do the same with the sending units.  I boil them both for a good amount
>of time, then extract one and take a resistance measurement.  It starts at
>about 35 ohms and slowly climbs to about 45 to 50 as it cools.  The more it
>cools, the higher it gets of course.  I then extract the other one and it
>reads about the same, starts around 35 and begins climbing at about the
>same rate.
>
>Argh,  This indicates to me that both sending units are working, though
>they BOTH may be the wrong range.
>
>Okay, this next part is confusing and needs some accurate interpretation,
>so I'll try to accurately relay the symptoms.  Please bear with me.
>
>I install the new 'stat and the new sender (why not).  I then fill the
>radiator with the same fluid I drained earlier.  Due to what are probably
>air pockets in the system, I can't get quite all of it in.  I put the cap
>on.  I start it up.  Stupid me, left the temp sending unit wire unplugged,
>so while the car looked okay, I went about putting tools away and cleaning
>up.  Less than five minutes later (or less) I notice a waterfall coming
>from my overflow tube, what the hell?  Here is the important part, I feel
>the upper radiator hose... it's cold, but under a lot of pressure.  The
>fluid overflowing is luke warm, actually cool to the touch.  What the hell?
> I shut it down and hear gurgles and bubbles and all kinds of noises for a
>few seconds, then it all gets quiet.  I try to slowly remove the radiator
>cap, it's cold, at the first step it starts blowing cold radiator fluid all
>over so I tighten it back down.
>
>I start the car again and let it go.  The overflow has stopped, I continue
>to monitor the upper radiator hose, which I can now squeeze flat by hand.
>I must have vented enough pressure, but where the hell did the pressure
>come from.  Do I have a compression leak into the water jacket?  The engine
>continues to run, it starts getting hotter, I notice the wire hanging that
>should be connected to the sending unit, I attach it, and check the gauge.
>The temp gauge reads past two-thirds in the normal range and is still
>climbing.  I continue feeling the upper hose, it starts to get warm but I
>can still squeeze it almost flat by hand and I don't seem to feel any fluid
>flow.  The radiator is still pretty cool except for one spot about the
>middle which is starting to get pretty warm to the touch. (yes, the
>radiator is fine, I flushed it thoroughly before installing and it flowed
>very well).  Still no steam or any more fluid out the overflow.
>
>I check the gauge, it's reading slightly over the top of the normal range,
>just one neede-width away from the "H" mark. (limit of travel for the
>gauge).  The upper hose is very hot but I can still squeeze it and it
>doesn't seem as though it's flowing, at least I can't seem to feel anything
>going through it.
>
>So I grab a thermocouple probe I brought home from work. I place it next to
>the temp sending unit on the front of the engine, just under the thermostat
>housing.  it reads less than 190 as I hold it there for quite a while.
>That tells me it's NOT overheating.  Okay, what the **ck over.
>
>Soooo........ any ideas?
>
>- Why did the radiator overflow cold fluid?  Was it air pockets in the
>block expanding under the pressure of warming up? and forcing fluid back
>through the water pump inlet?  Until the thermostat warmed enough to open
>and equalize the pressure? (no, I forgot to drill a small hole in the stat
>to help bleed air, DOH!)
>
>- Why does my gauge read too high?  Is it really too high?  Doesn't jive
>with thermocouple reading taken by hand.  Would both brand new temp senders
>from Napa be wrong?  I sat with thier rep and made darn sure I had the
>correct one.  Could the factory be packaging the wrong ones?
>
>- Why was I able to squeeze the upper hose when warm, is that normal?
>Shouldn't it get harder to squeeze or at least shouldn't I feel fluid flow?
>
>-  Could it be my gauge has gone south?  The instrument voltage regulator
>might be a culprit, but all the other regulated gauges read okay, so I
>don't think that's it.  The gauges though haven't been used for three
>years, could it have developed corrosion?  Would throw the reading off?
>Corrosion = increased resistance, increased resistance = lower temperature,
>therefore corrosion = lower temp reading on gauge.  I guess that doesn't
>make sense then.
>
>Ack... I'm all confused, I need a tech session with the experts.  I've lost
>my confidence in troubleshooting this thing.  I also don't have confidence
>in driving the car if it is indeed overheating.  I'd hate to ruin this
>brand new engine.
>
><sulking off his soapbox>
>Asa Jay
>: (
>
>
>