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TR6 TR6 enine running hot - need some adivce

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I

ichthos

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I have about 1,500 miles on my 69 TR6 engine after a total rebuild. Ever since the rebuild the temperature gauge needle goes up to about 2/3 once the engine warms up. Before the rebuild, it typically was a little less than 1/2. My questions is where should the temperature needle be? How do I know if there is a problem with the gauge verses a real problem with the engine temperature? Any help would greatly be appreciated.
Kevin
 
Have you got the mixture dialed in? You'd be surprised how much hotter the engine runs when the mixture is lean.
 
I would not suspect the temp gauge since the only thing that changed was the engine rebuild. I'd check all fluids and the belt. How about the water pump... is it new or is the original one back in? Make sure it's working properly.
 
Timing and carb adjustment have effects as stated Kevin.
Get yourself a temp shooter dealy. Check the temp at your hoses
 
Do I just point one of those temperature devises at the hose? What is the correct temperature? Even when my engine was not timed or the carbs not adjusted correctly, it never did this before the engine rebuild. I will have to go back through my records to see what was replaced.
Kevin
 
Kevin:

The temp reading on my 76 TR6 is just under the half way mark when it's warmed up. I would check the things mentioned on the above posts and if they all check out ok, then I would be looking at other things that got changed during the rebuild such as the thermostat. Just because its new, doesn't mean it's good!
 
Check the easy things first - the thermostat and the timing. Pop the thermostat out and make sure it opens at the right temp (185 deg?). You can use a pot of boiling water and a cooking thermometer for this. And timing too advanced or retarded will cause overheating - around 10 deg BTDC static should be about right.
 
DNK said:
Timing and carb adjustment have effects as stated Kevin.
Get yourself a temp shooter dealy. Check the temp at your hoses
Click to expand...
Do all that. In fact do everything you can to eliminate the cooling system as the culprit. Then,if you are still running hot, advance the timing using a Vacuum Gauge to guide you.
 
Kevin,

Is your gas gauge reading high? If so your voltage stabilizer, or whatever is the proper name for the device that controls the voltage to the Temp and Gas gauges, may be bad. If the gauges are getting 12 volts they will read higher than if they are getting the 10 volts they are designed to get.
The device is a small metal box similar in size to some flasher units or even some large fuses used in American cars. It should be mounted on one ot the long screws holding the speedo in the dash. I believe the speedo screw is also the ground for the device. If it is not mounted so that the case is grounded it does not work as required.
It is on the back side of the dash.
If the stabilizer is not working your engine may actually be operating in the correct temperature range but you are seeing a higher temp on the gauge.

If anyone else has a better description of the device, it's name and function feel free to add to the discussion.

BOBH
 
It is called a voltage stabilizer. Do you know how to test it? Never really understood how it worked. All I know it one time I did have this fail and my gauges just stop working. The only other gauge that is behaving oddly is the amp gauge. It tends to swing up and down considerably. I had seriously thought about getting one of the solid state voltage stabilizers one and for all.
Kevin
 
Ok, here's an off-the-wall crazy guess based on your last post. Any chance your alternator is putting out well OVER what's needed...say, upwards of 15-16v? I don't know if that might be the cause of your ammeter's mood/needle swing, or whether that higher voltage could "overpower" the voltage stabilizer?
 
The original stabilizer should be able to handle a good deal of voltage, at least 20v or so. The aftermarket solid state replacements might have a problem at higher voltages (because they would get hotter and potentially overheat) but the original design should be OK.

It also would not affect the ammeter, unless perhaps there is something shorted on the output side of the VS.

The stock VS contains basically a coil of resistance wire wound around a bimetal strip that in turn controls a pair of contacts. When the strip is cool, the contacts are closed and power is applied through them to both the resistance wire and the output terminal. When the coil & strip get hot enough, the strip flexes and opens the contacts, interrupting power to the coil & output. It's tweaked so the long-term average is 10 volts, but if you connect a meter, you will see the voltage swing between 0 and full battery voltage.

Easiest way to check is to pull off the lead from the temperature sender on the thermostat housing, and connect a test light between the lead and ground. Turn the key on, and within a few seconds the light should start flashing on and off. If so, chances are good that the VS is working OK.

Another good test is warm it up with the radiator cap off and a thermometer stuck into the water. That should show you both whether the thermostat is working, and once the thermostat has opened (indicated by a sudden jump in temperature), the relationship between actual temperature and what the gauge reads.

Just a thought, was the temperature sender replaced as part of the rebuild? What about the ground lead between the engine and the chassis? If the ground strap is missing, it might show up as a high reading on the temp & fuel gauges.
 
What was done to the engine? Did you bore it out 40 over, shave the head, install a header? Also did you have the block boiled out to clean out the water jackets? All these things can add up and cause it to run warm. I did all the things mentioned above except for the header and my engine has run a bit hotter ever since.
 
Pretty sure all he did was fix the head this time.
Didn't you have temp issues on a trip you took , Kevin?
 
Just curious: What color is the insulator on the temperature sending unit? Red? Black? My red went to 3/4 the black went to 1/2. Same exact VS, gauge, etc. Both being sold as a GTR108. I went to a bit of work to verify that the red sender unit was 'causing' high values at the gauge. I think BPNW sell the black. I bought from Rimmer.
Tim
 
Tim just asked the same question that I was going to. I had the same issues with those two slightly different sending units. I found a black one at one of my local Napa's. The red one is still sitting in the top of my tool box and I don't even own a TR6 anymore.
 
To clear up some info, the engine was completely rebuilt. I got tired of fixing one thing after the other and just bit the bullet and did it correctly this time. All the typical parts were replaced in the rebuild, including the temp sending unit. I had an excellent spare crank that was only ground 10 over. The block was bored 20 over. The original head was so bad I had to swap it with a spare I had. According to the machine shop, the spare appears to never have been rebuilt before. The engine was boiled out. The radiator was checked and cored the year before, so I figured it was probably OK since it wasn't over heating.

By the way, I just went in the garage to check on the insulator in the temperature sending unit - it is colored red. Can this problem be that simple? I can't remember where I got the red one, but I think I will order one with the black insulator from BPNW. I will start simple and move to check out other items suggested. Thanks for your help everyone.

Kevin
 
Never replace all the external bits when you do an engine.
Water pump, if it's got a problem, okay, or if you know the new one is right.
You replace the senders, now you have gauges reading wrong, and where do you start looking?
I had more guys work for me who wanted rebuilt starter, alternator, carburettor, fuel pump, new senders, yadda, yadda, yadda, and when it wouldn't start or run right, where do you start looking?
Put all the old externals back until you get it going, THEN if you have a problem (carbs, starter, etc) change them one at a time and see what it works like.


I mean, yeah, if you had known carb issues, get that done, but if it started, and ran, and the gauges read right, now what do you have?
Do you still have the old sender?

Keep the old ones, in the original box, labelled "old-good", you now know what is in the car (part number and source), and you can swap the old one back in if you suspect something ain't kosher.
 
TOC, I am a pack rat and normally keep all my old parts. Unfortunately I did not keep the old temperature sending unit. BPNW does not carry the sending unit, so I guess I will try my local NAPA tomorrow. I'll let you know how it turns out.
Kevin
 
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