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I hope this doesn't mean something bad is about to happen .... [B)]

My temp gauge has always been rock solid at about 3/8 up to 1/2 when in traffic , but last week decided to ride at half under normal driving and during the weekend the gauge shot up to 3/4 after only a short drive. (It's still relatively cool outside, were no where near seasonal temps)The car still appears to drive ok, the upper rad hose is hot, the lower rad hose warm, anti-freeze level ok. I changed out the thermostat tonight with a new unit, and flushed out the coolant (4 years on 5 year Prestone)the antifreeze looked nice a green still, I also rinsed out the rad with the hose and ran water through the thermostat hole through the block , again clean!
After refiling the system and cheking the level , the gauge went right bad to 3/4 and stayed there even on a highway road-test.

Up until last week, the gauge was fine .....I've had the car on the road for over a month and half this year.


Any ideas???

Ron.

Sender units do go bad. Also, maybe the relay to run the electric fans are not working. Also, each fan has a separate fuse.

Clay

[url="http://www.jclay.me/"]My Triumph Site[/url], [url="http://www.triumphtechnical.me"]Technical Stuff[/url], [url="https://docs.google.com/folder/d/0B8MWEvqOpX3udEF4SmFQUW9RS09hbU5uNW5Wd0xrUQ/edit"]My Public Folder[/url],

Yes I would check the sender unit, Ron, and its wiring connector.

Tony

<font size="1">1981 TR7 FHC Cavalry Blue
1980 TR7V8 DHC Jaguar Regency Red - sadly sold!
1977 TR8 FHC EFI Factory development car Inca Yellow</font id="size1">

Hi Ron, I would be checking the actual temperature at the thermostat housing. If you don't have access to an infrared temperatures gauge I'd buy one. They are only about $20 in Oz so probably cheaper over there.

When my water pump impeller was slipping mine told me I had a problem with water flow. I could check all over the radiator with the engine running.

I had a large difference top to bottom, from just on 100C down to 40C, told me there was almost no flow. In my experience when running at that 1/4 to 3/8 on the gauge the lower hose is quite hot. Not too hot to touch, still too hot to hold. That was with the thermostat housing reading 88C. Unfortunately I can't remember the actual temperature.

In another car there was a large cool patch in the radiator, indicating a blockage. I think the things are worth their weight in gold.

Do you have a thermo electric, or viscous fan? On the 8, after little use a one year old high quality fan had lost contact with a number of segments in the commutator, & was running at only about half speed.

Hasbeen

PS. No water at the water pump drain slot I hope?

H

Hi Ron,
I posted the solution last week to a temperature problem on my 8. It was a faulty thermostat. It was only opening slightly at the correct opening temperature but then would not fully open. Eventually bu using a saucepan & temperature gauge it showed that out of 3 NEW thermostats only one opened fully. Could be your problem.

yeah I am wondering about the thermostat (new part defect is a possibility...)

I'm going to bring the car into work today and check it with one of the techs infrared gun. I passed water through the rad top to bottom and from both sides last night and water passes right through,
if the rad was blocked, would the water not have backed up/block ???
The upper rad hose is very hot, the lower hose I can definitely hold on to...I'm most worried its the pump, can they go with no warning and/or weeping?
-Btw it's the standard vicious clutch fan, and it seems to be working fine, I'd imagine that the temps would have gone down on the highway had the fan been week/no turning at the right speed ??

Also I was reading up in the archives (sp?) yesterday, if the sender or connection plug were defective/dirty , could it make only a partial increase in gauge reading [?]

Ron.

Ron, from your description it does sound like the coolant is not circulating properly. Possibly your new thermostat is not opening fully? You could test that like Sautie suggests or try another one! Make sure the replacement has the "jiggle pin" in the foot.

Before you take it apart, it could be an air lock in the system from your refilling. From cold, let it warm up with the pressure cap off, once the thermostat is open squeeze the hoses to see if any air is expelled. Feel the rad for any localised cold spots that might suggest a blockage.

Lastly yes the temp sender connector can affect the gauge reading since it works on resistance, anything that changes the resistance e.g. a dirty or corroded connection will affect the gauge reading.

Tony

<font size="1">1981 TR7 FHC Cavalry Blue
1980 TR7V8 DHC Jaguar Regency Red - sadly sold!
1977 TR8 FHC EFI Factory development car Inca Yellow</font id="size1">

My pump that failed, [impeller not tight on the shaft] was a brand new pump. I can't imagine one with a bit of age becoming loose after years. More likely to seize on, & be unable to remove without braking in my experience.

It is supposed to be pouring here tomorrow, some nearby areas got 4 inches today, but if it's not too bad, I'll take mine for a run & take the temperatures of everything. I doubt idling in the shed would give a true response.

I believe with mine the pump seal failed, & it dumped a fair amount of water out our magic slot, then overheated & blew the head gasket. The temperature gage did not get above half, yet when I stopped the thing was boiling. Like quite a few cars, if the water suddenly drops, the temperature sender no longer has water to read the temperature from.

I was driving my fathers Mitsubishi Gallant when the pipe going into the back of the pump sheared off. The temperature gauge dropped slightly, not climbed. The only thing that saved it was water was squirting out so fast it was wetting the plugs making it miss slightly. I only stopped to check the miss, & found water going everywhere.

Hasbeen

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by silverseven</i>

-Btw it's the standard vicious clutch fan, and it seems to be working fine, I'd imagine that the temps would have gone down on the highway had the fan been week/no turning at the right speed ??
<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Not much to add here. It's not the fan as temp would go down on highway. When Ron (Orange Rag) had his fan clutch fail, he took his fan belt off and drove home from Portland with no problem.

- - -TR7 Spider - - - 1978 Spitfire- - - - 1976 Spitfire - - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

Just looked on Ebay for the infrared thermometer and there are lots on offer for less than £10 including postage. Just had to order one at that price.

Russ

1980 TR7 Sprint DHC
Dursley
UK

http://tr7russ.blogspot.co.uk/

I checked the temp with a borrowed gun today and naturally since a front counter worker doesn't get the chance to be under the hood often, had more supervisors than you could shake a thermostat at (bad joke [B)])


So even though the gauge seems to be lying, the car is definitely not overheating, I literally checked the temps all over the rad and motor and they appear to be normal.
The coolant is flowing better now, guess the air working it's way out, ( therefore I'll put the waterpump merit badge on hold for now [;)])
It appears to be electrical either the gauge or a contact , out with the cluster one more time I guess ......

BTW, anybody happen to have a late-model N/A spec wire diagram of the temp gauge handy ??
(there must be many versions I'd gather???)

<blockquote id="quote"><font size="1" face="Century Gothic, Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by TR Tony</i>

Possibly your new thermostat is not opening fully?
Make sure the replacement has the "jiggle pin" in the foot.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

the thermo in the car had this wax like substance attached to it's ring (possibly the original one) the replacement I got was identical except it only had a kind of giggly spring without the wax part....could this make a difference?


Cheers guys

Ron.

Sorry Ron with it cold wet & misty here, I could barely get mine to 1/4 on the gauge, even with the aircon running, BRRRR.

At that the readings were

Thermostat housing, by outlet hose, 78C
Top hose 64C
Radiator
Top 74C
Half height 72C
Bottom 58C
Lower hose 48C

This gives perhaps a comparison, but at that I could even hold the top hose, with the lower one just nice to warm my hand.

At that I had better change my thermostat to something hotter, that is really a bit cool to run at, coming into winter.

From your last post your problem is of the better sort, no overheating, just gauge problems. May be difficult to find & fix, but nothing compared to an overheated motor, & a blown head gasket.

Good fun, ferreting in those electrics, I don't think.

Oh, did they offer you a transfer to the workshop full time, now they know you can open a hood?

Hasbeen

Yeah, with family responsibilities , I'm trying to keep the car running on the road ....don't want major resto work until later on [;)]
And I would rather pull the engine and do it right only once , then have to piece meal repairs
(because I know with everything else going on around here , once the car is taken apart, it might take years to finish [B)])

And to answer your last question , lol I'd much rather stay in the front end of the shop [:D]

Ron.

A long shot Ron but where does your temp gauge sit when turn off your engine does it sit below or above the first white line.
If it is now sitting above the white line then the gauge will give a false reading

www.classiccarrunblackpool.co.uk

1981 DHC 2.0 Litre
1980 DHC pedal car
1976 FHC 2.0 Litre

good question, I'll have to take a look !

You know, in thinking about it, I recently shampooed the engine , maybe that might be the root of the problem....
Guess the first connection I'll clean is the sender, then work my way through to the cluster. It might take a little time though as my oldest daughter is graduating next Wednesday + I'm working shift @ the shop over the weekend.

The way the gauge climbs fast, then sits at 3/4, I'm really leaning towards a gauge/wire issue. With the gun my actual temps were almost dead on what Hasbeen quoted.

Thanks to everybody for their insight!!!

Cheers

Ron.