Cooling issues...
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  1. #1
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    Cooling issues...

    Help needed! Bear with me, its going to be a long(ish) post.

    I have a 2005 Mk2 ZR, done 100400 miles on the clock. Head gasket changed at 80000 (according to previous owner, although he couldn’t provide proof). Recently, after fitting a stainless Scorpion exhaust (hopefully not a contributing factor as it sounds awesome) I’ve run into a bit of a cooling issue.

    On county road drives, the car temperature behaves, staying just below the mid line on the gauge, unless going up a hill when the fan kicks in and drops it back down. On motorway drives, I have issues. I’m having to put the blowers onto full just to keep the engine temperature from going beyond the 3/4 line. Ive done a coolant bleed, which chased out air bubbles and replaced the fan thermostat because I had one.

    I’m beginning to suspect that I may have a radiator that needs replacing, and along with it the normal thermostat.

    Ive had a few “Mates” tell me its head gasket, but a sniff test done at a local garage has come up negative for that.

    My questions are....

    1} would a flush through of the system be a good starting point?
    2} Would an exhaust cause these issues to surface??Previous exhaust was beyond knackered with al the baffles failing.
    3} Rad fitting, is there a way to do this without removing the front bumper?

    Any help, gratefully received!

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  3. #2
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    IS you coolant dropping?
    Was it ok before you put the new exhaust on?
    Sniff test don't mean anything, i know as mine went even with good signs of it not going.
    which rad? you got the a/c one on the front and the big one behind it is the main rad for the coolant.

  4. #3
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    Coolant level isn***8217;t dropping so there isn***8217;t any leaks. It used to spike occasionally before I put the new exhaust on. Yes its an AC radiator.

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  6. #4
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    Did you test the thermostat before installing? pan of hot water test?

    If you have a/c it would mean the alternator will have to come off for the main rad to be replace but unless you got a leak or when you changed the coolant you found crap in the coolant that came from the rad you will not need to replace it.


    The fan comes on now and then and the rad/coolant needs to be really hot for it to come on as its not set like other cars.

    a flush could help but are bad for the gaskets. you could flush with just water a few times but not letting it get too hot (most mg sites i've been on say its better than the bottle flush stuff) are you fully sure all air is out? letting it heat up and leave it to cool then let air out and repeat till no more air?

  7. #5
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    Can't see the exhaust being a probably unless it was blocked. Never had any coolant problems after fitted any exhausts before

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  9. #6
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    A sniff test will only tell you if the head gasket has failed at the fire rings, and exhaust gases are getting into the coolant. It can only be used as an aid to confirmation of this as there will always be some hydrocarbons present in the coolant, and it won't tell you if the head gasket has failed between coolant passages and oilways (any contamination here should be apparent from emulsified oil in the expansion tank, under the oil filler cap or on the dip stick - If you are losing no coolant, that rules out this mode of HGF anyway).

    From what you describe, it sounds more like a coolant circulation issue - possibly the rad has got blocked up with rust/general crud. If coolant is circulating through the radiator, the air flow through the front grille when travelling at speed will be more than sufficient to keep things cool. I would start by draining the coolant, and then remove both top and bottom hoses from the rad and flush it out well with a hosepipe (both from the top and upwards from the bottom). It might be that sediment in the rad has become compacted and won't flush out, so may need a new rad. Also be prepared to need a new rad anyway - if it is old it may spring a leak after flushing out. While the hoses are off, give the rest of the system a flush through with the hosepipe (the thermostat will stop the flow, but if you are intending changing it anyway, do the flush through once it is out).

    If it were the thermostat sticking, it would overheat at low speeds as well as higher revs. There is only the one thermostat (behind the engine, below the inlet manifold). What I suspect you have changed is one of the coolant temperature sensors - there are two in the coolant elbow at the front of the engine; one operates the temperature guage in the instrument binnacle, the other sends a signal to the engine ecu to trigger operation of the radiator fan.

    The water pump is also worthy of consideration - normally they give very few problems, but there were some cheap aftermarket pumps around a few years ago which had a plastic impeller, and these were well known for breaking up after a while, which of course means there is nothing to push the coolant around. As this will mean the timing belt needs to be removed (and possibly replaced), I would try a full flush through and see if that cures the problem first.

    Agree with John - changing the exhaust will not have any effect on the engine cooling (and other engine problems would be apparent of the exhaust were restricted or blocked).

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  11. #7
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    Thanks all. Looks like I***8217;ll be doing a full system flush tomorrow on my day off then! I***8217;ll give that a whirl and see what comes out. Many thanks

  12. #8
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    So, had a full rebled of the system today at a garage, where they also replaced the thermostat (the middle part of the old one had disappeared).

    Now, Ive still got the issues of overheating, but less so. Seems the cooling fan on the inside of the radiator doesnt want to kick in often enough. Ive had that particular thermostat changed as well (for good measure) and the fan does work when its disconnected from the system and re connected. Im now thinking its relay based, but, the fan does stop and an audible click is heard when the fan stops after Ive shut the engine down and waited 10-12seconds.

    Still confused!

  13. #9
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    As my above reply the engine has to get really hot for the fan to kick in, Very bad design if you ask me.

    If the click is coming from the glove box then it could be a bad replay or one on its way out.

 

 

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