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Asking for help with a new overheating issue

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mlarnoldTR6

mlarnoldTR6

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I have a stock 75 TR6. I drive it for weekend fun. She has been flawless for the past 2 years that I've owned her. This Fall after a routine 2-3 hour cruise I put her in the garage and the next morning I saw a LITTLE puddle of coolant on the floor. I checked the hoses and radiator and could find no trace of a crack or leak, no coolant in any of the cross members or other pockets under the hood. Recently on a nice afternoon I thought I would go for a ride. Within about 1 mile of home I noticed the temp gauge approaching the critical level and took her home arriving with steam issuing from under the bonnet. When I lifted the bonnet there was steam leaking out from the top of the water pump where the thermostat is located. Now my thought is that the thermostat is stuck closed or the water pump is caput. I don't think the radiator is the issue as no steam was coming out from the cap. The water pump belt feels snug. I would appreciate any thoughts on how to trouble shoot this issue. Many thanks in advance. /ubbthreads/images/graemlins/cheers.gif
 
Pull the thermostat and run the car. If problem persists, thermostat is eliminated as the problem. I struggled with an overheating problem all summer. I had back flushed the system with no evidence of rust, but running a commercial flush ended the problem. Simple process and effective. You may have to repeat several times or take for a professional job. From there, you just have to eliminate each component one at a time. Water pump, radiator(look for internal corrosion), timing(most likely not the problem), etc. At temperature, feel your top and bottom radiator hoses. Both should be warm to touch. If the bottom is cold, you have a rad problem. Good luck.
 
By commericial flush do you mean the
Prestone stuff you can get at an autoparts store?
also if you pull your water pump check to see if it is free spinning. I just removed mine and I noticed that it wasn't as free spining as I thought it should be. Upon investigation I
found that the gasket had been compressed so much that it was under the impeller and the flange that is used to bolt it to the engine. I cleaned it up and its spins freely now.
 
If it is moving freely, I would assume that it is fine. I have become a strong advocate of eliminating the paper gaskets in exchange for rubber based RTV products such as Permatex Good Stuff. It sets up by the time you get everything strapped back together and does not leak. Also works excellent around oil. No gasoline. The gasket, I was told, becomes the weak link and can weep fluid.
Yes, I started out with Prestone, and then moved to Zerex. Prestone suggests running the car for approx. 20-30 minutes while Zerex suggests 6-8 hours I believe. A friend claims to have used CLR with excellent results, though I have never tried it. It is recommended for cleaning rust deposits in home water systems, so I imagine in a dissolved state, it would be safe in a car. It would be considerable cheaper.
 
My buddy, who owns a commercial and industrial rad shop, advises, "Be very careful with chemical flushes in older systems and in general. The chemical can etch thru weakened components, such as heater cores. You may find leaks developing in very nasty locations" He has suggested that if you are in a warmer climate than ours, you may want to consider bypassing and draining the heater entirely.
 
[ QUOTE ]
Chemical flushes are nice. Backflushing is also nice. Trust me, though, neither necessarily cleans out the block. Read through the "Electric Fan Question" thread for more (rather than repeat it here)!

[/ QUOTE ]

agreed - pulled the block drain off mine and it was clogged solid about 3 inches into the block. I was able to chip away at it with some baling wire and finally got it open - THEN the disgusting stuff finally started to flush out. I'm just hoping there isn't another passage somewhere just as clogged that I couldn't get to. But my overheating seems to be cleared up so I'm keeping my fingers crossed.

Another web article I can't find right now says to flush with the prestone stuff, drain, fill with water and a box of baking soda, take a spirited drive for an hour, flush clear, and then flush one more time with prestone.

Apparently radiator flushing opinions are right up there with motor oil choice and religion... People seem to be rabidly fanatical about their choice.
 
But... back to the actual question. If steam was coming from the water pump area then you've got a problem there. Pull the thermostat and see if it opens in a pot of boiling water on the stove.

If there is too much pressure in the system it SHOULD be coming out of the radiator cap. That is the only point that pressure should release. Elsewhere means a bad gasket at the thermo or the pump.

What is the pressure rating of your cap? Could it be stuck and causing the pressure to release at a weaker spot? (unlikely I think because usually they fail to the weak side and just blow coolant rather than hold it back).

Someone will jump in but I seem to remember the TR6 cap should only be about 12lbs.

If it was a weak seal at the thermo housing then after pulling it and confirming that it works you might get lucky and fix it when you put a new gasket on to re-install the thermostat.

You could also get some of that flourescent leak tracing dye at an auto parts store to confirm exactly where it is leaking if it still happens after confirming that the thermostat is good.
 
In recommending that one pull the thermostat and run the car for awhile, the result might be that you never really get up to operating temperature. A better choice would be to take the old thermostat apart (remove all the guts) and leave only the venturi-shaped funnel intact. This will assure that the proper water flow volumn is maintained for the water pump and the engine will achieve proper temperature. Zero thermostat means zero restriction, not a good thing.

Bill
 
[ QUOTE ]

If there is too much pressure in the system it SHOULD be coming out of the radiator cap. That is the only point that pressure should release. Elsewhere means a bad gasket at the thermo or the pump.

What is the pressure rating of your cap? Could it be stuck and causing the pressure to release at a weaker spot? (unlikely I think because usually they fail to the weak side and just blow coolant rather than hold it back).

Someone will jump in but I seem to remember the TR6 cap should only be about 12lbs.

[/ QUOTE ]

Hi,

I agree the cap should be checked. These are often overlooked and really should be replaced every few years. If the cap doesn't properly release excessive pressure, it will eventually find its way out somewhere else!

I happen to be putting together a TRF order right now and took a quick look: They specify a 13 lb. cap for 1973-76 TR6, and a 7 lb. cap for 1968-72 TR250/5/6.

The cap should have released pressure before steam found its way out elsewhere, but there is still some blockage or problem somewhere in the system. Things need to be checked out: t'stat replaced, hoses aren't collapsing, system might need a flush, maybe even the radiator needs a core job done on it.

Please keep us posted on what you find.

Happy new year!

/ubbthreads/images/graemlins/cheers.gif
 
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