Temperature Matters - Mental Challenge

[MikeHurley]

Well do you ever get that feeling of 'Deja Vu' with my 2.5l V6 ?

Four Years ago about 6 months after the Cam Belts were changed at 134k miles had the misfortune to experience over heating and water loss, and to be told incorrectly by a Garage in deepest Hampshire that it was HGF.

However thanks to a second opinion and the wonderful diagnosis of "Lates 600" it was the dreaded plastic Thermostat which needed replacing and indeed the Fan motor which was dead.Both replaced at that time and joyful driving has largely been experienced ever since. As a precaution I ordered and received a Kaiser Stat and Housing which will possibly need installing soon I suspect from heating behaviour over the last couple of days.

In late Autumn it was serviced but I notice gurgling in the heater matrix which gurgled more with increased Revs. and there was the annoying imbalance of heat output to the passenger side, but the Temp no matter what seemed to generally be anything from 88 C- 96 C, until the last couple of days.

Over the last couple of days, the temp on motorway driving seems fine being in the 92 c-94 c, however driving slower or being stationary the Temp increased to the extent 2 days ago when I parked up and let the engine run on for a minute , water was being expelled from the expansion tank (about a litre I would guess). Topped the resevoir up yesterday morning with about a litre. Then last evening after coming off the motorway on the way home from work, I had to pull into a Cul de Sac, and the Temp suddenly jumped to 105,107, 113 and 117c at one point with Fan on double speed. Drove home only a mile from that point and the Fan continued and temp remained at 107 until I parked up, and then came down to 96 before I switched the engine off!

This morning, I checked the upper hose to the expansion tank and it felt unusually pressurized, I released the expansion tank Cap and as I was doing this coolant came out of the overflow only about 100ml, and there was a faint hissing after the cap was removed. The expansion tank appeared fine in terms of Coolant level so I replaced the Cap before setting off to work (journey of 13 miles on motorway speeds 50-75mph) Temp generally stayed at 94c until parking up and it moved up to about 104-105c before I switched off the engine.

As I was switching off the engine I noticed idle Revs unusually dipping and normalising a few times. So off with the engine.

I was tipped off yesterday about an MG Garage near to my workplace in North East Kent (MG Apple's) who have a T4 and cater for forum members preferentially. However, the earliest they can have the car in is next Tuesday (5 days time), and I fear for the old beast in the interim.

Could this kind of temp fluctuation behaviour have been caused by an airlock in the heater matrix moving into the engine block and residing in the Thermostat Housing? or something totally different, like manifold gasket, Oil Pump failure. Listening to the matrix before setting off the Gurgling was much less pronounced than last week but I could hear water movement which indicates to me the water pump is still functioning.

Views please, as I have tried to be as accurate about the symptoms as possible and T- minus 5 days to line up the possible causes and understand the possible solutions...............or would the T4 deliver all the answers once the beast is connected for the 1st time?

[David3807]

Mike,

Have you considered possibility of stuck thermostat partially open/closed ?? And have you checked the engine between the 'v' for red staining - ie split stat casing.

Would also be a bit careful about driving the car if its going to 117c. These engines are pretty strong but that temp is very close to you getting the emergency overheat signal which I think is at 118c.

With a car that was showing 134k four years ago (and a present mileage of ???) you could be pushing your luck a little ie towards real HGF


David

[T-Cut]

A pressuried cold system isn't a good sign. After standing overnight, there should be no pressure at all in the header tank. This applies even if there's an air lock. Something has pumped up the pressure to about 20-odd psi while running and is remaining at that pressure when everything's cold. It's typically HGF or a liner issue. The high temperatures may well be due to exhaust gas being injected into the coolant.

TC

[MikeHurley]

Thanks Guys for that, I am now feeling very cautious about the Beast, and am tempted to leave it stationary for 5 days.

[MikeHurley]

...........oh present mileage circa 192k!

[MikeHurley]

During the autumn service, compression and smoke tests were carried out and I was given to understand engine was good and given a Bill of Good Health, that was after I'd overfilled the Oil and lost compression a week beforehand!

However, I cant wait to have it on the T4 in 5 days and understand what if anything is happening inside the Beast.

[James.uk]

Apart from old readings-fault codes caused by the cars prev problems, I doubt the T4 will be much help as you don't mention any icons coming up on the dash..

If --- worst case scenario.. A head gasket is blown, it will be cheaper to replace the engine than have it repaired...

An added bonus of that is you can do all jobs that need doing like belts, thermostat, water pump, etc with the engine on the bench..
...

[wutang]

Mike, apple are usualy quite good, my thermostate failed closed on the way to work in feb and I was able to limp the car to them, no appointment and I asked them to have a look at it when they could, they called me 5 hours later and it was fixed by next morning.

If you are really worried I would suggest asking them if someone could give it quick look over to put your mind at rest.

Richard

[MikeHurley]

No Icons came up on the Dash I am pleased to say, (other than the Red Seat Belts one which has been like that for the last 3 years, and has remained like no matter how much the yellow connectors have been off cleaned etc).

Well its been 6 hours since I parked up at work so I will now pop out and see if there is still some air released by opening the expansion Tank Cap, checking water level. Then I will see if the idling bounces up and down if I turn it over for a couple of minutes.
This will determine whether or not I leave it at work and ask for a lift home later!!

[MikeHurley]

Well, Started her up. Temp slowly and normally went from 40c to about 65c before I pulled off from my parked position. Went for a drive of no more than a mike and did not exceed 40-45mph, temp went to about 92 after 2 mins driving.

Then on the return run to car park position, temp started to climb to 100c, then 104c before pulling back into Car Park, and remained stationary and switched off engine. Sat there and heard distant bubbling/boiling.

Stepped out of the car to see water spilling onto the ground and noticed behind the car a wet line along where the car had turned into the parking bay. Obviously coolant leaving expansion tank before

There is an overheating and Coolant Loss problem from the Expansion Tank Cap, as the rim of the tank had green coolant in it too.

Damn. Looks like lift home and possible Rescue of car to Garage on or before next Tuesday ,,,,, AA today if the garage will have it for a week!!