22 replies to this topic

[Andie]

Hi all,
Long story short.......
I have a '97 mpi which is losing coolant and the fan keeps kicking in for long periods.
I've replaced the head gasket, thermostat, water bottle cap, water pump and flushed the coolant.
The heater in the car works fine, the rad seems to heat up ok and no blockages. The car seems to drive ok, but I am now at my wits end to fix this issue. Any advice would be seriously appreciated guys.....think I'm gonna have a nervous breakdown!

Thanks
Andy

[Dylan8660]

Try a 70/30 mix of coolant (70 of coolant)

[Yoda]

try doing a pressure test to see if you can identify where the coolant is going.

Edited by Yoda, 29 October 2012 - 05:24 AM.

[bluedragon]

When the car gets hot, is there bubbling of air in the coolant recovery tank? If there is, then there surely is a physical problem. The worst case is a warped/leaky head. If you're lucky, maybe you just got a bad coolant bottle cap (though you just replaced it, sometimes even the new ones can be bad too.) I hope it's the lesser of the evils.

I assume the lost coolant is overflowing from the bottle, but if it's just disappearing from somewhere, I would be worried about the head/block sealing (warped head.)

[Andie]

Thanks for the help guys. This is getting to me now. As the heads already been replaced, might try replacing the bottle itself and all pipes. It was overheating massively and boiling out the cap, so thats when I got the head gasket sorted but although the coolant stopped boiling I'm still losing a lot. Also the temp sender is not reading it as overheating on dash so I think that needs changing but I've been advised this is only a sender to the dash and does not control the coolant.

[firstforward]

Thanks for the help guys. This is getting to me now. As the heads already been replaced, might try replacing the bottle itself and all pipes. It was overheating massively and boiling out the cap, so thats when I got the head gasket sorted but although the coolant stopped boiling I'm still losing a lot. Also the temp sender is not reading it as overheating on dash so I think that needs changing but I've been advised this is only a sender to the dash and does not control the coolant.

You have not replaced the head, just the head gasket, the issue might still be with the head that was overlooked before, do as Yoda has suggested, I have even had a head develop a hairline crack within the exhaust port....that was a hard one to find.

[firstforward]

Try a 70/30 mix of coolant (70 of coolant)

Try fixing the problem first!

[Dylan8660]

Try a 70/30 mix of coolant (70 of coolant)

Try fixing the problem first!

How do you know it's not the problem? The poster wasn't clear about where the coolant was leaking. Do you know if they are even using a water/coolant mix?, no? so try the basics first. Coolant will raise the boiling temp, the car will take longer to overheat giving more time to find the problem or a solution.

[firstforward]

Try a 70/30 mix of coolant (70 of coolant)

Try fixing the problem first!

How do you know it's not the problem? The poster wasn't clear about where the coolant was leaking. Do you know if they are even using a water/coolant mix?, no? so try the basics first. Coolant will raise the boiling temp, the car will take longer to overheat giving more time to find the problem or a solution.

If somebody is not using antifreeze and just pure water, the engine should not overheat, we all know that. In this situation the cooling system is losing pressure and as a result allowing the water to boil, or the fault is allowing the system to overpressure and forcing water out to a point that not enough is available to continue cooling the system. Adding antifreeze not only is it costly and unnecessary adding to a potential repair bill, will not give any significant advantage because it will not prolong the time to expel the water if the engine has failed in such a way that it is pumping water out. If on the other hand water is being lost by an external leak or internal leak the pressure will drop and the water will boil at a lower temp than if a solution of antifreeze was present yes, but the engine would now be low on pressure, losing water most probably internally ( if externally that should already have been found as an easy fix so why add antifreeze before the fix is found unless you can use a bright fluorescent liquid ) so where is the advantage to find the fault? ( you cannot "work" on a hot engine)because no amount of running of the engine in this state will fix it. It needs a good old fashioned cooling system pressure test to see if any external leaks have appeared or if any liquid has pooled in a cylinder or any other part of the engine. A pressure test itself is not always a direct way to find a fix, sometimes a crack can appear and is only "leaking" when the engine is hot because the metal has expanded, but closes sufficiently when cold to make a seal so a cold pressure test will not necessary find this type of fault. Only then should a removal of components be considered to visually inspect components and other avenues of fault finding tried.

[Badboytunes]

if it physically isnt leaking out of the engine ( onto the ground for example ) but is boiling and losing water I would suspect the head gasket. Is there any excessive steam /water comming out of the exhaust? Usually if a head gasket fails into the combustion chamber you should be able to smell the anti freeze in the exhaust fumes. Did you get you head skimmed while it was off? Although not a necessity on an iron head, it is always worth doing, just for peace of mind. Heads can warp when released from the block, even when cold. When the engine is warm do you get hot air out the heater? Check to see if both heater pipes re hot too.

Do a compression test, that miht help.

[Dylan8660]

From the Haynes manual,

Auxiliary cooling fan

Models with front mounted radiator:

Switches on at 105°C

Switches off at 98°C

If you want to run pure water as the cooling agent in a mpi then good luck but you will have problems, it will boil and leak, new cap or not.

Furthermore we don’t know if the original poster has done their own work on the car but it strikes me that somebody with the insight and capability of changing the expansion cap, thermostat, water pump and head gasket would be beyond any knowledge that might be imparted on this site.

Edited by Dylan8660, 09 November 2012 - 07:37 PM.

[tmsmini]

An MPi is no different than an earlier A series with a presurrized radiator cap. The cap will release pressure based on the pressure in the system not its temperature. The coolant/antifreeze affects this tempearture but not the end result. As said you should be able to run plain water with no issues in the short term. Long term the anti corrosive chararcteristics of the coolant are beneficial.

I did have a very small hairline fracture of the expansion tank that could not be seen, but it was leaking and providing a pressure release and the subsequent boiling.

The temperature sensor in the thermostat sandwich also sends data to the ECU and provides the trigger for the fan as well as sending data to the gauge.

Terry

[Andie]

Hey guys,

Sorry for the late reply to your posts.
I've been running a mix of 50:50 coolant:water in the car since I flushed it when I first bought it. The rad fan comes on fairly quickly after setting off.... once the engine gets to full temp it switches on a few minutes later so I know that the temp sender is working(I replaced it myself). The water in the bottle isn't boiling over at all since I got the head gasket done and put a new cap on it. There aren't any visible leaks on the car but I will admit that the bottle does look a bit knackered. The temp gauge only ever goes up to the half way point in the car, so I'm gonna sort this out asap as its such an easy fix to replace the sender. Once I've replaced the bottle I'm gonna get the car pressure tested to see if this helps figure out the problem. I would be fairly confident that the head was done properly(didnt attempt it myself) cause the guy I brought it to is a mini specialist and put a lot of extra effort into making sure other things were ok on the car too. Does anybody know the rough cost of a pressure test?

[Dylan8660]

The temp gauge wont really go over half way in normal running. It sounds like your fan is working normally. You've stated that it no longer boils up but your still losing fluid, is this from the expansion bottle? Could it just be finding its level after all the work thats been done? My level settles just under the seem.

[sport2000]

Check header tank, if there are visible spider cracks in the header tank this could be the problem, as you maybe losing pressure and the system is a pressurised system,causing boiling over...replace the header cap also with a genuine version,even though you have replaced it these are known to not fit correctly causing boiling over..

Just my thoughts and only suggestions