Well the trusty old girl has been back on the road this morning for the first time since she went into my garage before Xmas! All running sweetly after new head gasket and new rad (old one blocked solid with oil).
Still one concern , the radiator fan is coming on when the temp guage on the dash is reading normal. She started doing this before she went terminal, so am concerned there is still another problem I've not found or fixed yet. Is there a seperate temp sender for the radiator fan? I've found the one in the head just before the thermostat housing that sends to the guage on the dash, but I'm worried there's a hotspot in the cooling system caused by something nasty that is causing another temp sender to start the fan, when the dashboard guage thinks all is well.
Any thoughts???? Any help appreciated by me any my F!!

Usually the temp sender for the fan is situated in the radiator Rob either at the bottom or down the side pillars

Mmmm, no electrical connections on the rad at all. Only wiring loom comes to the fan motor, so it must be on the engine itself. Could it be near the water pump housing to measure the temp of cooled coolant coming into the engine from the rad?

The temp gauge hardly ever moves from normal whether the fan is on or not. How often is the fan comming on?

Just check there's plenty of coolant in the system as well.

Mark

Hear Hear !!!! My temp guage reaches the middle within about 2 blocks, and never really moves from there. The fan came on yesterday after a particularly exciting drive home from work, and when I checked the guage, it was STILL in the middle !

In quarter of an hour of hooning it around a race track, never at less than about 5000rpm on a hot summers day (those of you at Japfest last year will know how hot it was then!), the needle didn't budge from the normal position!

Mark

Although, when a caned it away from my mates house on sunday, within 2 miles the gauge had gone up to 3/4!!!!!!!

Unheard of, so i slow down, needle returns to normal, stop get out, engine not even that hot?????

Baffled, hasn't done it since

I hope you didn't cane it from cold!!??

Mark

8-[ who me???????????

yes you :P

My fan comes on every now and then when it gets too warm but as everyone else has said - the temp gauge dont move at all stays mid range all the way

might be worth bleeding your water system - not hard as I think theres a bleed screw on one of the pipes - else undo the rad cap and let the air come out until the pressure drives the water to the cap and do it up. The air locks in the pipes can cause funny readings - dont discount the loss of water when this happens though - i did this in a volvo and realised a pipe had split and the system was running on empty - by this time though, we'd already blown the head gasket :-S

Thanks Brad, actually, could be an air bubble in there from when i fitted the new coolant temp sensor!!!!

Thanks all for the feedback so far.
The fan is coming on when parking after a short drive, and on a chilly scottish morning with lots of cold air flowing around the rad, it shouldn't need to.
Could be an airlock. I left one of the small water pipes up to the inlet manifold/air intake disconnected when I filled her up to try and let the air out, but will try Brad's tip of running her without the rad cap on to try and get any more air out.
I was wondering if the oil contamination could've screwed up the temp sender, but it sounds like it's performing normally (ie not moving much!), so guess all is well.
Would still like to know what switches the rad fan on so I can isolate it as a problem.

Will try bleeding tomorrow and take her for another run and report back!

Also try squeezing the Rad 'top pipe' when she's hot to try and get the air out of the system. Make sure the reservoir tank is topped up as well - it's quite a good indicator

Mark

Thats what puzzled me, the overflow bottle level hasn't moved at all???

Checked for airlocks / squeezed pipes this morning and seems ok. Rad topped up + expansion tank. Took her out for a blast down some fast Argyll roads (remember them Mark?) and all seems ok. I forgot how much fun 2nd gear and 5000rpm is! Nothing from the fan until I was home and she'd idled for a few minutes.
No sign of oil emulsion in the oil filler cap (phew!). The level in the expansion tank may have dropped a little. I'm about to drain and refill the coolant again to clear the remains of the oil that's stuck in the heater matrix etc. Will then refill to full and keep a VERY close eye on the level.
Yesterday there was still traces of steam/white smoke from the exhaust, which I had a horrible feeleing could be burnt coolant. Barely any today, hopefully a good sign. I've still a horrible feeling that there's a nasty surprise lurking somewhere, eg a crack in the block or in the head that I couldn't see. Will report back soon!

Yeah - I remember them - Too young to drive back then and the last time I was there I was in a hire car with a sensible person driving

Some promising results there then. Good luck


Mark

For all you mechanics (or should that be maniacs?) out there, latest update on the health of my F.
Still running very sweetly (good!). From checking the underside of the filler cap there’s no sign of water contamination in the oil, and the level on the dipstick hasn’t dropped (also good!). The rad fan seems to be behaving at the moment too.

However (you knew there was a ‘but’ coming didn’t you!), the coolant has been contaminated by oil. Not the thick gunky stuff like before, but it’s definitely gone a milky colour. The level in the expansion tank has also dropped about 10-15mm after running for an hour or so in total. The exhaust is also showing wispy white steam, not billowing smoke like before she went in for surgery, just looks like the normal condensation at start-up. This isn’t there immediately, but once she’s started to warm up it appears and then is there all the time.

So, I’m left with the following thoughts:
Is the coolant contamination still from old contamination stuck in the heater matrix etc? The pipes to the heater matrix go ‘downhill’ from the engine to the bulkhead, so when you drain the coolant from the rad bottom pipe, I guess the heater matrix will stay full. Is it reasonable to think that it’s still got oily gunk in it and that just flushing the coolant a few times will get it out? Or is it more likely there’s still fresh oil getting in there?
The condensation in the exhaust and the dropping coolant still suggests there’s an internal leak. Would the fact that it isn’t there at start-up suggest there’s a crack in the head or weep at the gasket that’s only opening up as the head gets hot? The head was pressure tested when the gasket first failed in September, but I guess that’s done cold. Is it worth re-torqueing the head bolts in case there’s a small weep somewhere?

So I’m now trying to work out what to do. I don’t want my F to die , as although she’s got 120k + miles, she’s worth more to us than scrap! Any suggestions gratefully received!!
Thanks.

well if the coolant has been changed then usually it may drop, due to air still in the system, they may bot have bled it through properly, also if they didnt use correct fluids to flush the cooling system through then maybe it still has some oil in it, the best thing to do is to ring a mazda dealer and get some advice, there the ones that will know best, if you take it back to the garage you got the job done at then they might feed a load of crap to you.

the only way you will be 100% is to carry out a pressure test to see for any leaks, if none are visible then carry out a block test. this will then tell you if your head or head gasket is damaged.

also did they change the oil and oil filter when they did the head gasket?

Latest health report on my trusty F, and it's not good!
Running very smoothy, but oil level has dropped by approx 0.6l in 2 weeks. Coolant level unchanged but now have thick oil emulsion under rad cap. No evidence of oil emulsion under oil filler cap. Still got white/grey smoke from the exhaust, lots of thick smoke at start-up then wisps while running.
My non-expert conculsion is that oil is getting into the coolant (hence oil emulsion and dropping oil level). The coolant level in the expansion tank hasn't moved because there's over half a litre of oil gone in there and half a litre of coolant burnt off out the exhaust! Sound like a reasonable conclusion?

If so where do I go from here? If the coolant is getting into the chamber to be burnt, is it a cracked head, or could it be the block? How is the oil getting into the coolant? What's involved with the block check that Pyro suggested? Have I reached the end of DIY mechanics, is it time to take her to a specialist, and if so, am I likely to need to re-mortgage?
Your thoughts as always apprecated.
Cheers all
Rob & poorly F

Dude, i'm gonna assume you used the correct tightening sequence for the head bolts. Di d you check the head and block for cracks when it was in bits, sounds to me like a crack if everythings been done by the book. Was it a genuine replacement gasket set you used????

Yep, used a torque wrench and followed the sequence as posted on here. Had a good look for surface cracks with a torch while it was in bits and there was nothing apparent. It wasn't a genuine Mazda gasket but a japanese manufactured one.
I've had the plugs out and had a peek down at the top of the pistons. I would guess that if coolant was leaking into the chamber it would pool there after the engine stopped running, but can't see any liquid.
I'm tempted to run her with the exhaust manifold removed to see if I can identify which cylinder steams like the Ivor the Engine!! Shouldn't do any damage should it (as long as I have ear defenders on!)?
Am really baffled as oil is getting into coolant, AND coolant into the chambers. How can that be???? Arrrgggggghhhhhhhhh!!!!!!

ave you checked the colour of the plugs, that might give a clue as to which pot its leaking into!!!!

I wouldn't run it without the manifold on if i were you, not withstanding the noise, there will be very hot flames coming out

Ok, fair point, prehaps not that good an idea then!!
A couple of plugs looked sooty, 3 & 4 I think from memory. Rest nice & brown. What does that suggest, will burning coolant cause sooting?

Don't like to say this but it sounds like a failed head gasket....

Well that was the conclusion I had almost come to, so nice to know someone else is thinking the same Mark!
Decision now made, back into my garage to get the head back off. Will double check for any warping, and this time I am going to use gasket compound when i stick it all back together (even though I know I shouldn't), just incase there's some flaw somewhere thats allowing a leakage path across the gasket.
Here we go again, at least I know how to get it all apart this time!
Wish me luck, this is one F that I'm not going to let die!



Now where's that torque wrench gone............

I don't think you should use any kind of compound with a head gasket. I'd cough up for a genuine Mazda one though. You also need to ensure that the joining surfaces are PRISTINE.

Anyways, best of luck....

[quote="Rob"]...this is one F that I'm not going to let die!



Now where's that torque wrench gone............[/quote]

That's the spirit

Good luck Rob.

Mark

Also, you may find the metal in the head or block has become porous, i've heard of this happening to bikes before, you can't see anything when you inspect it, but when its all put together and running, the pressure can force liquid through the metal!

Very hard to diagnose.

Try another head????

Sounds to me like the blown head gasket diagnosis it the likely suspect, when u have the head off it would be worth while getting as much of the machined surface areas "dye pen" inspected, this involves throughly cleaning the casting, spraying on a normally red penetrant dye, leaving it for at least 10 minutes then throughly cleaning it off. A developer spray is then applied (fine chalk type powder) and any cracks that have retained the red dry is reabsorbed back into the developer, giving you a visual indication of where the cracks may be. Good place to get his done would be any Non Destructive Testing business that maybe in your area, and its the cheapest way to identify defects, and a very quick process.
If any corrosion or pitting is present between coolant/oil system communication ports on the head, then consider getting the mating surface of the head lightly skimmed. Most defects should skim out with less then 0.020" (0.5mm), if not then I would consider the head to be in pretty bad shape and you should consider sourcing a better one.
While the head is off, its worth while checking the valve seats also, for burns and surface finish. Its always worth the extra time to regrind the valve seats too while you have access to them, and source and replace all the valve stem seals while you have the valve springs and caps off.

As Marky Mark pointed out, any mating surfaces on the head and block should be pristine and assembled "dry".

Also apart from using the designated retorquing sequence and values when you are reassembling the head, It is highly recommended to retorque the head after the engine has been run and brought up to temperature and allowed to cool. Dont take the car past 2500-3000 rpm during the warm up process, because if any warping is present, this will only casue leakpaths to develop through the softer gasket material, and reduce the chances of curing the problem.

Hope this helps