Thermostat Puzzle

[DJT]

My Stag has been running with an 82*C thermostat since I bought it. With a good VC, a flushed system, Volvo header tank and an LD Parts temp sensor, it runs just below half way on the gauge in Summer, but around 1/4 in Winter. With the ambient temperature falling again I thought I would fit a hotter 'stat. Today I bought a QH 'stat for the Stag and this one is stamped 89*C. It is the correct one for the car with the by-pass foot and a jiggle pin. Having fitted it and taken the car for a test, the indicated temperature is lower than it was with the 82* 'stat.

[milothedog]

My Stag has been running with an 82*C thermostat since I bought it. With a good VC, a flushed system, Volvo header tank and an LD Parts temp sensor, it runs just below half way on the gauge in Summer, but around 1/4 in Winter. With the ambient temperature falling again I thought I would fit a hotter 'stat. Today I bought a QH 'stat for the Stag and this one is stamped 89*C. It is the correct one for the car with the by-pass foot and a jiggle pin. Having fitted it and taken the car for a test, the indicated temperature is lower than it was with the 82* 'stat.

Never seen an 89* Dave but perhaps it is allowing better circulation than your old one did.

Ian.

[flying farmer]

I was trying a variety of old thermostats in a pan of hot water a while ago, three at a time.
Some opened when they were supposed to, some were a few degrees out, but what suprised me was the variation in width of opening a few degrees over the temperature at which they initially opened.
In the end I chose the one which opened widest soonest, and the temperature gauge is far steadier with the 88 degree stat than it was with the slow opening 82 degree unit it replaced.
The temp initialy ran one quarter of the gauge higher with the 88 degree stat but the fuel gauge was over reading so I swapped the voltage regulator for another second hand one.
The temp gauge now runs in the same place, however the fuel gauge never quite reaches full now and I suspect it may read a fraction low, however it is closer than it was before.
Neil

[DJT]

Problem solved

Had a 20-mile drive on Saturday in near-zero temperature and the temp gauge never rose above 'Cold'. Today I removed the 'stat cover and found that when I fitted the new 'stat it had slipped whilst doing up the cover and 1/3 of the 'stat aperture was uncovered. Basically it was acting as if there was no 'stat fitted. Oops!

Re-fitted it properly and now working as it should. Quicker warm-up, temp gauge needle at the halfway position and a decent heater again.

What a plonker.........

If anyone needs an 88-degree 'stat then the Quinton Hazell QTH117K is the boy. QH don't list the Stag, but cross-referencing the vehicles they list for this 'stat against the application list for LDparts FTK010 shows it a match. A surprising number of vehicles is the same 'stat:

QTH117K.pdf