I recently bought a 6 with a broken cambelt, and rebuilt the head in my spare time at work, I've now had it running a couple of weeks but still have a few little problems I can't get round, and with buying the car with the snapped belt I have no idea how it ran before hand.

Firstly the temp gauge says its running at 75-78 degrees even after an hours drive or so, it has on occasion reached about 85 when stuck in heavy traffic, I don't know if that is the gauge at fault or if it is actually running cold, but I replaced the thermostat with a new 83 degree one. I thought it may be a faulty one and stuck open or similar so went to buy another one off the reg number this morning and they have given me an 88 deg one saying thats what comes up, surely this is too high?

The next two are most likely related (along with the 1st) but from red light to red light I am only doing 300 miles, where compared to my other 6 I was usually getting 400-440 to a tank (489 was my best). Is this normal and the other one was exceptionally good on fuel even with doing 60k more?

Every now and then it gets hesitation when I put my foot down, Only done it a few times so far but its as if I've let my foot off the throttle momentarily, along with cutting out quite a bit when cold and returning to idle (used to this from my 205). Is this likely to be related to the other problems? and in what order would you check things? As my other 6 is sat on the driveway I am able to swap most things over as long as they fit.

Cheers

Thanks for the response, I've swapped over the 2 coolant sensors this evening incase it was one of those being faulty. I've come to put the coolant in and as I fill it up with the engine off water started coming out of the thermostat bleed screw then just after the top rad bleed screw, am I right in thinking that if this is the case with the engine not running and cold the thermostat is stuck open?

Also as the only one i was given when I ordered a new one was an 88 degree thermostat, is that alright to use or not?

No, that doesn't mean that it is stuck open.
Coolant will come out of the top of the rad, the thermostat housing and eventually the matrix bleed point.

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61k miles Ph.1 Diablo '6 Project Thread