Question-------------------------
Followup To
Question -
Gee, I just found this site/service - it seems wonderful! Even before anyone takes any interest in my predicament, let me give my sincerest thanks to all those who make it even possible to submit.
Subject car is a 1969 TR6, one of the first imported. Generally stock, except dual Webers. Radiator shrouds in place, multi balde fan working fine, etc.
This is my 5th TR6, so I've been through a thing or two with them. I had several when I lived in Arizona, and always loved that they ran cool, or at least not hot, even in the brutal summer heat there.
Along with this "not only a question", I'll ramble on about some general ideas I'd appreciate any input on.
I THINK I have a cooling problem. The motor has been flushed (a few times) and coolant appears to be flowing free. (Yes, the tube from the heater along the right side of the motor, that frequently causes problems, has also been given attention and is fine). New and proper thermostat (again, even replaced a second time with a straight from Moss Mtrs good one). New good cap, new temperature sending unit. All the basics. (The problem exisited before installing a new wiring harness, at which time the shop claims to have tested all gauges - we found and replaced the faulty ammeter).
When the car is running along (at road speeds) the temp gauge fairly quickly goes up and into the red. It also quickly drops to (barely) acceptable, (meaning 3/4 mark or so - but below the red), when the car is let to idle. Yes, it actually drops down while waiting at a light, or if I coast it along at turnpike speed.
The car never actually appears to be overheating....it doesn't lose or blow off a drop of coolant or huf & puff. (Hence the reason I'm not sure if it actually is overheating). But as the gauge responds so well, dropping down responding well if you run water over the radiator/motor, I tend to think the gauge should be believed.
What else should I be doing to identify or cure the problem?
Some thoughts/ideas:
Running unleaded, (this is the first one I've had with hardend valves so I can), means I'm burning fuel hotter than the car was expected to. Hence cooling becomes more strained.
I've seen ads for radiator core rebuilds that claim they can use the new super honeycomb type cores and increase cooling substantially. Maybe a worthy option?
I see oil cooler kits, which seem to be modestly priced and a fairly easy install, especially considering their benefits even without suspect engine cooling. (I've already got the spin on oil filter conversion). Cooling the oil should help cool the engine I would think?
How can I check the actual temp of the cooling system without scalding myself to death in the process? (I can't figure out how one sticks a thermoter into the system while its hot/pressurized). Can one just buy any old working temp gauge (probably easy enough to find a cheap one) and hook it to the existing temp sending unit (and some power), to check its not a faulty reading on the the in dash gauge?
Finally, once secure with this, I want to put an electronic ignition - Petronix or the like - (and appropriate coil) in. Any opinions on this, or which unit is best, or to avoid? Note, I'm aware timing and setting can cause some cooling problems, and I'm confident they are good now. But if you think the Elec Ig may solve the overheat issue, I could do it sooner instead of later.
Thank you for your thoughts....and please... I really won't mind if its just an easy solution!
Jeff
Answer -
Jeff,
There are three causes that will make a car overheat.
1) problem with the cooling system
2) Carb mixture incorrect
3) Ignition timing off
A couple of leading questions, maybe I can help pinpoint where to continue your troubleshooting:
You don't mention whether the radiator hoses have been replaced. One possibility is that the lower radiator hose is collapsing due to the partial vacuum caused by the water pump pulling the water from the bottom of the radiator. That will effectively shut off the flow of cool water, hence your problem.
When you're driving along with the temp gauge getting into the red... does the car still run "normally" or does it make any hiccups? Running rough, hesitation, misfires?
Have you checked the ignition timing to make sure it's correct?
And have you checked your sparkplugs to see what kind of mixture you're getting?
Other things to do to check:
Consider swapping in a mechanical temp gauge, at least temporarily. These guages have a sensor bulb and a thin capillary tube to the guage... you can test it before you hook it up by dipping the sensor bulb into a pot of boiling water and verifying that it reads correctly.
You might also consider putting your thermostat into a pot of boiling water to see when (and how far) it's opening.. it's not unusual for one of those to be bad.
You don't mention whether the radiator itself has been cleaned/tested. Corrosion and mineral deposits can block off the tubes in the core without the radiator leaking or looking obviously bad.
As to electronic ignitions and ignition timing, has the existing distributor been checked for proper operation of the vacuum advance/retard units(not sure which setup you have) ?
Cheers,
Jim
Jim,
Thanks for the speedy response - boy we got us one heck of a thread here!
1)Yup hoses are no more than a few years old and appear in good shape - (of course now that you mention it, I'll see how they feel when hot).
2)The car runs normally even when saying hot...normally..not perfectly! But no, there isn't any particular roughness, etc.
3)At least 2 mechanics have checked the ignition timing. (The car spent much of the winter at the shop - new head gasket, carb setting & linkage, along with the wiring harness, etc. - they checked, and last summer another guy did too. Neither said that it was particularly off.
4)Sparkplugs were a mess when changed with the head gasket, but probably related to the carbs. Webers didn't have the right vacume breather set up and one would seem to get oily - fixed).
5) I had never heard of a mechanical temp gauge (obviously I'll check my local places). How does it connect. But, would hooking up a different gauge to this sending unit, (as a friend or two may have an old gauge laying around the garage) work too?
6)I'm pretty certain the thermostat is working right. I've been through several with the same result.
7)Radiator was pressure tested. Looks good. Hence, not needing a new one, the idea of the new "super" core was an extravagance
8)My distrib is good...actually a rebuild from reliable rebuilder 2 years ago. Retard works and all...again... one of those thiongs I'm in no rush to change to elec Ig, but it seems everyone says it's well worth doing.
Thanks again,
Jeff
AnswerJeff,
Most of the autoparts stores used to carry mechanical guages...
Another idea would be to get one of the probe type thermometers and gently set it in the fins on the radiator when the car is at temp. The core of the radiator should be at approximately the same temp as the rest of the cooling system (ok, a bit cooler as it's the heat exchanger... )
The electrical gauges draw power from a voltage stabilizer that's usually mounted on the back of the speedo or tach (at least on Spitfire, need to look at the TR6 manual again). If the stabilizer is bad then you'll get funny gauge readings.
If you're going to use an "old" gauge from a friend, make sure it's known as good. No point in going though the effort to hook up a bad gauge.
I'd look at the plugs (again) and maybe have the car emission tested to see how the mix is. A compression check might offer other clues too.
The simple answer is that you're either making too much heat, or not getting rid of it effectively. Or being mislead by a faulty gauge/sender.
Was the temp sender tested? Changed?
Do you have a voltmeter in the car?
At this point I'm not sure what else I can suggest.
Cheers,
Jim
