Hi all.

My first post - I have recently acquired what I believe to be a 1993 KR Magna 3.0V6 auto station wagon; you'll have to bear with me, as I am in England and only 500 were apparently imported between 1993 and 1994. The chassis number begins 'KR2P45...' which may hopefully make some sense to some of you! (Indicates to me from the Mitsi workshop manual that it's in fact a 1992-model Verada?). The car is badged as a Sigma rather than a Magna/Verada, with the 6G72 SOHC engine and 3-speed + OD autobox.

Anyway, great car, bought as an interim vehicle and only cost the equivalent of AUD500 so I can't complain. However, it does seem to have a cooling system problem - there's a lot of pressure and it occassionally seems to boil a bit (say 0.5L) of coolant after a long, hard (lots of revs and/or 160kph on the highway) run - when switched off, a hot jet will shoot out of the overflow pipe on the reservoir tank. Opening the rad cap gently will result in a lot of bubbling noise, once open it can be seen that the coolant has a bit of foam in it.

Even if the car doesn't have a hard run, upon opening the hood there's a little bit of steam (not from anywhere specific, just around the passenger side of the engine) and a fair bit of heat, but it doesn't appear to use any coolant in normal operation.

Symptoms and current progress as follows:

1. Thermostat and rad cap replaced - rad drained (top and bottom hoses removed) when the former changed, no crap/carrot soup emerged. Refilled with 40% coolant/distilled water mix.
2. Top and bottom rad hoses appear to get equally hot.
3. Car has been run up to operating temp with rad cap off (including a bit of revving) until thermostat has opened to try and remove airlocks. No major bubbling noted. Expelled water when revved seems to indicate water pump is still operating.
4. No mayo in the oil filler cap, excess steam or water dripping from tailpipe, and cabin heater works very well - so I don't think the head gasket has gone (was done recently anyway - not by me thank God, the Mitsi dealer charged the previous owner AUD2000 for the work, including skimming the head and recoring the rad).
5. Temperature gauge sits bang-on halfway when warm - does seem to warm up pretty quick though (10 mins/10kms from a cold start). When the car was first acquired, in traffic the gauge would sometimes go up to 3/4 then drop down to 1/2 after a couple of seconds, but since I changed the thermostat it just winds up to 1/2 and stays there, regardless of engine/car speed?
6. Radiator fan seems to cut in properly when the car is idling/stood still.

A friend who considered himself an expert on 'Jap cars' (:nuts:), thought the thermosensor on the fan had gone - it cuts in when stood still, but I can't tell if it is working when on the move.

Maybe that's next for replacement - unless anyone else has any ideas?

Just for a while ...

Take the thermostat out, put a new gasket on, forget about the economy for a while.

Drive around for a while and check what happens.

Then start bench testing the thermostat in boiling water. Do it a few times and see if the spring has lost its "spring" and in fact it might close half way with no change to the water temp. (on the gauge in the car)

Does the radiator have coolant in it, glycol that is, not just water?

Me thinks also, top hose and bottom hose should be different temps. Have you got a cooking temp dial gauge "thingy" (that you put in cakes etc, cheap as to buy) that can be put on the outside of the rubber radiator hose to check the differences in temp. Bottom hose should be cooler than top hose.

Welcome to the club

Cheers

So other than the pile of water that comes out when you shut it off is it loosing any water..??

To me it sounds like a Thermostat if its dumping water when you turn it off.. If it was a leak it would have the pressure to dump when you shut it off.. Easiest way yo tell is after 10mins of drivng both raiator hoses should feel the same in temp(roughly).. Feel both top and bottom radiator hoses to see what they are like when its been running for a while.. If they are the same its all good with the thermostat, if there is a vast diff the thremostat isnt doing its job..

Proberly first thing i would do ir remove thermostat and all have a really good look at all the hoses to make sure there isnt a water leak anywhere.. Also make sure there is no water leaks or drips from around the water pump..:)

Thanks for the thoughts chaps. The old thermostat's spring felt knackered, whereas the new one felt much more compliant when I hand-checked it before I put it in. Top and bottom hoses are definitely the same temp after 10mins of running. The water/glycol mix is 40% as per MMAL manual (we get a bit colder here in the UK!).

I have a spare gasket so might try taking the 'stat out again and see what happens. Interestingly, the steam seems to rise around the water pump area, but I've not noticed any major leaks, drips or noise, and from the rise of water out of the rad (with the cap off) when the engine is revved, I guess the water pump is still working? It doesn't seem to lose any water unless it's been really hooned - I guess it still gets hot (hence the steam/heat) but maybe the steam then condenses back into water as it cools down?

Unfortunately I'd say that if the pump is gone, the car won't be economically viable to fix :cry:

Just one more thing to check is the overflow bottle. If its past the max it will definetly spit the water out.

Regards

Yeh

The water pump is dead easy to do on V6's. Get a workshop manual (from Library) and away you go. You don't have to buy genuine pump.

How many kilometers or miles on the engine?

Cheers

ok check these out. is ur cat coverter blocked making the engine get hotter than it should thus giving u probs with the cooling system.
have u had the radiator out so it can be back flushed incase of a blockage. have u changed the water pump cos the bearings might have rusted out making to cooling systen run hotter seening as the water pump might not be pumping enough through the system??

well that all i could think of for now:D

good luck and welcome to AMC

Thanks guys. I have a PDF of the 1995 MMAL workshop manual so I'll take a look at the water pump change, although there's no bearing squeal at all. Mainly I'm concerned about disturbing the timing belt!

Car has 170,000kms on it. Had the radiator recored two years and only 10,000kms ago, when the head gasket went. Will remove and reverse flush.

impeller fins on waterpump might be corroded, and chopping the coolant instead of pumping it.. worth a check!
i'd be careful placing a thermostat in boiling water, as that can destroy it.. opening temp is probably 88 or so degrees, so 100 degrees might be too much for the wax pellet!
personally, i wouldn't bother with a flush using a garden hose, id remove the radiator, have the tanks removed, and pipes inspected, that's the only real way to check for radiator blockages.
other than that, are there any leaves or foreign objects blocking the radiator fins?? or airflow?
worst case scenario, the headgaskets installed might be aftermarket, blocking water galleries from the block to the head!
the lads are on the right track though.. remove the thermostat, and check how it operates without it!

i'd be careful placing a thermostat in boiling water, as that can destroy it.. opening temp is probably 88 or so degrees, so 100 degrees might be too much for the wax pellet!

:nuts:

Boiling point of water at atmospheric pressure is 100deg (at sea level). Boiling point of glycol mixture is way above that, so the thermostat is made to cope with those temps. Alot of modern cars actually have a regular operating temp close to 100deg, which is why you can't use plain water in the cooling system.

Make sure you also backflush the engine too, aswell as the radiator. And double check that theres no external radiator blockages arund the fins. Could it be something as stupid as the wrong grade oil? or spark plugs? :confused: If it only happens under high engine loads... don't forget that mmal probably didn't intend on the car being driven at 160km/h for prolonged periods of time...

Thermostat should begin to open at 88 degrees C and be fully open at 100 degrees C.

Rob

Can't see any foreign objects blocking the rad. The oil grade is an excellent point - I haven't done a change so I will buy a filter and get to it.

I did notice earlier today that, at running temp, the level of coolant in the expansion tank is pretty high (almost to the top, and above 'MAX') so that may have something to do with it...I'm not sure whether coolant is making it's way back from the expansion tank to the rad when the engine cools down.

:nuts:

Boiling point of water at atmospheric pressure is 100deg (at sea level). Boiling point of glycol mixture is way above that, so the thermostat is made to cope with those temps. Alot of modern cars actually have a regular operating temp close to 100deg, which is why you can't use plain water in the cooling system.

Make sure you also backflush the engine too, aswell as the radiator. And double check that theres no external radiator blockages arund the fins. Could it be something as stupid as the wrong grade oil? or spark plugs? :confused: If it only happens under high engine loads... don't forget that mmal probably didn't intend on the car being driven at 160km/h for prolonged periods of time...


Thanks for informing everybody on your knowledge of thermodynamics, most valuable information i must admit! :nuts:
I think you will find that a 50 per cent mix of C2H4O + H2O → HOCH2CH2OH will have a boiling point of 106 degrees celcius, not much more than 100 degrees celcius at sea level!
Keep flipping those meat patties at Mcdonalds boy!
Anyway, no point going off topic, to check if you do have a problem with the head gasket/cracked head etcetera, remove the radiator cap when the engine is cold, and sniff inside the radiator filler neck. If you smell anything resembling a fuel/hydrocarbon smell, then sorry to say, you are in serious trouble! Water is mixing with combustion gasses.

:nuts:
Boiling point of water at atmospheric pressure is 100deg (at sea level). Boiling point of glycol mixture is way above that, so the thermostat is made to cope with those temps. Alot of modern cars actually have a .
Yes, but, even a 74 kpa radiator cap will lift the boiling point to 110 deg C. So you can run straight water if you don't mind the corrosion.

Rob

Thanks for informing everybody on your knowledge of thermodynamics, most valuable information i must admit! :nuts:
I think you will find that a 50 per cent mix of C2H4O + H2O → HOCH2CH2OH will have a boiling point of 106 degrees celcius, not much more than 100 degrees celcius at sea level!

Its exactly as Rob_D says... pressurising the cooling system raises the boiling point of the liquid by about 10deg.

Yes, then you can add on another 6 degrees to allow for the glycol.

Rob