View Full Version : poor gas mileage and maybe overheating

09-09-2006, 05:01 PM
Hello All:

I have an 89 XR7 automatic with about 55K miles on it. It is getting pretty bad gas mileage
(around 14-15 in town, premium gas only since I bought the car in 1990). It never did very
well in this regard, but is worse now. About five years ago, I had new plugs and wires put in
and have changed the fuel filter fairly regularly. It feels like it is missing. It is especially
noticeable in Park. I had motor mounts done a few years ago, but it didn't help this vibration
much, if at all.

The car also has a problem with possible overheating. If I drive it about 15 minutes, the temp
gauge is fine. But if I drive it for a longer period of time in the city, especially with the
air conditioner turned off, the temp gauge needle will slowly creep up to slightly above the 'M'
in NORM, and the idiot light 'CHECK GAGE' will come on until it cools off again. The car
doesn't have that many miles on it. Could the radiator be to blame here? I have fought with
this CHECK GAGE light and the TEMP gauge for a long time, and I had a used temperature
gauge put in early this year (the old gauge was completely shot). The used gauge I had put
in seems to work fine (Ford doesn't seem to have parts for our cars anymore).

I am not a mechanic, but any help would be appreciated.

Thanks in advance,


Kevin Varnes
09-09-2006, 05:28 PM
How often has the coolant been changed? When was the last time it was changed? Are you loosing any coolant (check the radiator when cold not the overflow tank for an accurate reading).

09-09-2006, 06:00 PM
Considering the age of your car (not neccessarily miles) you could be looking at the usual HG proglem we have.

When the HG's went on mine, it started to idle more rough and it seemed to heat up more than usual etc. I didn't have the huge white plumes of smoke out the rear, my oil was clean and the overflow had a gurgle once I reved up the engine.

Go to a local parts house and get yourself a leaking combustion test kit. It samples your coolant to see if there is combustion gases in there.

09-09-2006, 08:07 PM
Kevin: the coolant gets changed every few years, but probably not enough. I suspect I am losing
coolant, but very slowly. The car smells a little of hot coolant when I park it in the garage after
a longer drive. When the VMM flashes the light about the overflow bottle being low, I often add
a little (maybe twice a year).

Frit: I have thought about the head gaskets before too (been a lurker here for a long time).
If you have to have someone fix them (an independant mechanic), what would it cost?
I'll see if I can find the kit you mentioned. I have seen head gaskets go out on a friends Trans
AM, it smoked up the whole block. I haven't seen anything like this out of my XR7. I watch
the guys who have been doing my maintenace for years. To me, the oil always looks clean.
It is hard to imagine HG failure after 55K miles, but I am afraid you may be right.



Kevin Varnes
09-09-2006, 08:17 PM
HG replacement at a shop nowadays would probably run around $1200-1500. Frankly I wouldn't really trust anyone to do that on one of these unless they have worked on these cars before. HG's can leak without being completely blown. I would have someone check the coolant for presence of exhaust gas. That is about the only way to know for sure.