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mg_tf
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It was quite a while ago, so my recollection is a bit hazy. I may used the rubber seal off the old stat. Have tried that?
 

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mgf
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Discussion Starter #23
no worries , cheers luke, i will give the thermostat a trim with the grinder this weekend and cut it down enough to get the rubber seal on.

thanks
martin
 

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mg_tf
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Oh dear Luke, you are not serious about grinding the thermostat are you?

To me, the logic is simple :- if you have correctly dismantled everything correctly out of the assembly, and the replacement thermostat doesn’t fit, then it’s the wrong thermostat!
I would be spending my time trying to find out why it’s wrong/ getting another, rather than attacking the current one with a grinder.
Kind regards,
Austin.
 

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mg_tf
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That doesn’t sound right. I don’t recall it being an issue. I’ll see if I can find the original receipt that may give some details about the exact part.
 

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mg_tf
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Hi Martin, my apologies, I believe you need the GTS104 thermostat. This is 82C and should fit the housing without any mods. Rimmer Brothers have them for under £5.

Regards
 

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mgf
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Discussion Starter #27
ok, cheers luke/austin, i will go back to rimmers. only £5 so peanuts, luckily thermostat o ring washers over stretched so couldnt touch the thermostat this weekend waiting for the o rings to arrive.
 

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mgf
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Discussion Starter #28
hi
update - after installing the 82c degrees thermostat and checking all the rear water hoses for blockages i ran the car outside the house for about 1 hour idling and revving to 3000/4000 revs. heater got hot, radiator fan would kick in every now and then and needle stayed about 8 o clock on the gauge then all of a sudden after about 1 hour the temperature started to rise and the coolant started to boil even when i put heater fan on full while rad fan was running.

then i tried again the following day with the heater set to Cold and the car was fine, gauge stayed the same. i took it for a drive with the heater still on cold and no issue whatsoever so i am now at the conclusion the heater matrix is blocked.

will try back flushing next weekend if its not raining again, anyone know where to get to the heater coolant pipes? i seen the ones at the back of the engine but some users have said you can get to them underneath? i know if it need to change the heater matrix then its a dashboard out job.

thanks
martin
 

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mg_tf
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I’m sorry Martin, but I’m just not following your logic regarding a blocked heater core being the issue here. If you turn the heater control to cold then you are not allowing coolant to pass through the heater matrix - just as if it was blocked, or conversely, if it is blocked then it’s just like turning it off!
When you had it turned to hot, did the heater blow out hot air?
Did you bleed all 3 bleed points in order:- radiator, heater and then engine hose?
Kind regards,
Austin.
 

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mg_tf
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Hi Martin,

I tend to concur with Austin on the heater matrix not being the issue. I’m more suspicious of the front radiator. Here’s my logic. With the heater off, you have less water circulating in the circuit and the radiator and fan are able to dissipate the heat. However if the front radiator is partially blocked and with the higher volume of water circulating with the heater on, the partially blocked tad is unable to dissipate enough heat and the system boils over. Only a theory, but it’s worth removing the rad and checking the volume and flow rate through. You may be able to do this without removing the rad of course.

Good luck

Ps. I’m assuming the GTS104 thermostat was correct?
 

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TF135
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I've suffered from when a previous owner put that coppery coolant system leak seal gunk in my previous TF, perhaps as a 'permanent' leak fix :-(

Nether he nor the product were 'smart' imo and I'm sorry to say it doesn't seem to discriminate where to seal...
 

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mgf
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Discussion Starter #32
hi All

luke - thanks thermostat was perfect fit.

i understand all the doubts, agree doesnt seem to be logic in turning the heater to cold the car runs ok and doesnt overheat, only thing i have noticed when the heater was on hot and the car started to overheat there was always an air lock somewhere, either the heater would go cold and the car start to over heat, another time after driving it for 20 miles i turned the heater on it started to over heat and thats when i checked the outlet from rad and it was cold.

yes heater does run very hot when on. i am also bleeding via the correct 3 points. i will drive the car for the rest of the week with heater turned off and see, i do have my doubts and maybe you are correct, if its dry at the weekend i will do a reverse flush of the matrix, if still overheating rad removal and clean will be next.

cheers guys.
 

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TF135
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I've just read that jiggle valves serve to release trapped air to the expansion box side of the engine and that there's a second jiggle valve just below the cyl head on the rhs of the engine looking forward
hi All

luke - thanks thermostat was perfect fit.

i understand all the doubts, agree doesnt seem to be logic in turning the heater to cold the car runs ok and doesnt overheat, only thing i have noticed when the heater was on hot and the car started to overheat there was always an air lock somewhere, either the heater would go cold and the car start to over heat, another time after driving it for 20 miles i turned the heater on it started to over heat and thats when i checked the outlet from rad and it was cold.

yes heater does run very hot when on. i am also bleeding via the correct 3 points. i will drive the car for the rest of the week with heater turned off and see, i do have my doubts and maybe you are correct, if its dry at the weekend i will do a reverse flush of the matrix, if still overheating rad removal and clean will be next.

cheers guys.
 

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TF135
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Just a thought...
On the F/TF jiggle valves seem to serve the task of bleeding air from the inside to the outside of the engine/expansion tank (I think?). Apparently (apart from the img) there's a second jiggle valve just under the cyl head on the rhs of the engine looking back to front. I've never known about this before, yet alone 'cleared' mine, but could this be another area on your TF that doesn't allow an air pocket to clear - giving you these o/heating probs - I wonder? (In deference to the gunk in your t/stat)
(There's some interesting reading on this w/site...)
mgf.ultimatemg.com/group2/common_problems/hgf_pages/why_do_hgfs.htm

133892


Why do head gasket failures occur?


ttp://mgf.ultimatemg.com/group2/common_problems/hgf_pages/why_do_hgfs.htm
 

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mgf
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Discussion Starter #35
hi everyone,

thought i post an update. i have been running the car to station and back plus a few 30 mins trip around town and neighbouring towns for the last month now and i havent had any movement in the temp needle from one below half. Previously i would have expected to have a rise in temperature towards 3 quarters at least once a week in this time.

The last job i did was to back flush the heater matrix with the hose pipe, i didnt get chance to see any gunk come out so i dont know if the same gunk that had completely blocked the jiggle valve on the air filter side was present in the heater matrix.

the one thing i have noticed now is that the car now takes about 10 mins to warm up with the heater on, before when i purchased the car back in august one of the reasons i was convinced i had a issue was that the car warmed up to normally with 1 or 2 minutes with or without the heater on and this was always a concern before.

Whether its because the weather is colder now i am not sure but once i have taken on a long trip it might give a better idea as to if the heater matrix possibly being blocked was the cause.

thanks
martin
 

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mg_tf
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Hi Martin,

Tbat sounds like a good result. I'm guessing that you still have the 82C thermostat fitted, in which case it may take a fraction longer to get up
to temp over the 88C stat but 10 mins sounds right to me. I've been running an 82C stat o. My TF for 2 years now, but i relocated mine to the front, just behind the radiator. The logic being it will minimise the thermal shock to the head as there will be more blending of hot and cold before the stat opens. I dont use my car in the winter so Im not too concerned about the longer warm up time with more water circulating ahead of the stat.

Good job enjoy
 

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hi everyone

just thought i will post another update since the dec.

had various other issues since dec, had the sidelights fuse keep blowing, kept the car of road 2 weeks, found 4 or 5 all broken in the boot hear the hinge (common issue i have learned) the short in the end was caused by the centre console clock shorting on the bodywork when hit bumps in the road.

next issue was clutch pedal dropped about 2 inches, changed seals on master then also on slave as slave was leaking and allowed air into the system hence pedal not coming back up, least it wasnt the release arm.

the elephant in the room - overheating- i havent overheated/ or needle moved from normal for 3 months apart from once. have noticed since changing thermostat to 82c and flushing heater matrix i am losing about 1cm of water a week which means there is still a problem, noticed under the car when doing the slave a slight drip of red fluid so thats on my list over the easter holiday to look at. also noticed sometimes the water level in the header tank almost disappears only re-appears once you turn the engine off and undo the reservoir cap so i thinking there must be major air in the system. I also purchased a sniffer kit from ebay and have ran that twice and both times no change in liiquid colour so no exhaust present possibly. so at the moment i am losing water slightly and also overpressuring.

anyway what i am going to do next.

i have purchased a prt cooling system from a tf off ebay second hand so that will be going on in april.

i also purchased one of those low coolant level kits which sits on the outside of the header tank but until i sort out the disappearing header tank coollant i cant fit it as the alarm will probably be on/off all the time.

also when i fit the PRT i will take rad off and flush as i expect that still have the pink paper crap that i found in the jiggle valves.

after that if there is still a problem, water pump change (now that i have smashed the locking wheels nuts off). also thinking about the engine temp sensors replacing them.

also dishwasher tablets in the header to clean? anyone done that?

cheers
martin
 

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mgf
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Discussion Starter #38
hi everyone

just thought i post update.

after all the issues i have been having with intermittant overheating since i bought the car last july even though it had previously had the head rebuilt and mls gasket fitted, did a sniff test which didnt show exhaust gases present i have just replaced the head gasket as i found a small amount of mayonaise on the inside of the rocker cover. head was skimmed by 6 thou and pressure tested and another mls gasket fitted with new stretch bolts. i have attached photo of the old headgasket which you can see has come apart. so the 2 issues i had were i was losing water about 1cm per week and random temperature rising on the gauge about once every 2 months which meant i couldnt trust the car to take it on long trips.

when i put the car back together it wouldnt start, thanks to one of the members on here suggesting too little petrol which even though it had a quarter of tank once topped up with another gallon of petrol it started straight away so once corona virus has died down hopefully now i can drive it.

my thoughts on what caused all the issues? one of the previous owners putting some sort of rad weld in the cooling system which blocked the air filter side jiggle valve completely causing air locks which then caused overheating. car started fine, idled fine, ran fine most of the time with the old gasket in that state just lost a little about of coollant.

cost if anyone wants to know.

mls uprated gasket kit including new stretch bolts - £40
new water pump and cambelt + tensioner - £50
Head skim and pressure test & strip down re-assembly - £170
oil and filter - £30

thanks to everyone who has given advice over the past year almost.
 

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mg_tf
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That's great news. I hope we haven't missed the best of the weather and we can get out and enjoy our cars once it's safe to do so.
 

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1995 MGF Mpi
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Thanks for the update.

I hope you found the issue with the head gasket and the rad weld stuff.
 
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