Overheated while stationary

Sprint · 4 May 2023 21:59

My model of MX-5 is: 1990 Eunos Mk1
I’m based near: Milton Keynes
I’m looking for technical help or recommendations on: Overheated

Hi all

Had my MX5/Eunos for 4 days. Done about 150 miles in it in that time, and she hasn’t skipped a beat.

Decided to go out for dinner tonight with it, drove there and back without issue, but when we got home, due to only being able to open the garage door from the inside, the wife went in, through the house, had to sort the dog out, get down the garden to the garage to open the door. In that time, I sat on the drive with the engine idling, no more than 2 or 3 minutes. As she started to open the door, I suddenly spotted the temp gauge had risen rapidly. It wasn’t at the top yet but was getting hot. I quickly pulled into the garage and shut the engine off. Seconds later, a loud hiss, and lots of steam!

I’m not sure if the fans were running, they might have been, i didn’t hear them, but when i turned the ignition back on, they kicked in. The leak appears to be coming from a pipe under the intake manifold, behind the throttle body. I’ve circled it as best i can. the end looks rather crusty.

(for reference, its about here)

the pipe didn’t feel too hot to the touch, maybe because all the water had vented. There wasn’t alot of water on the floor.

I’m terrified I’ve cooked the engine, but as i say, it never got to the top of the gauge, maybe two thirds, and perhaps it just found an old weak hose that let go?

Looking for some reassurance and advice, does anyone know what that pipe is for, where i could get a replacement? It looks pretty hard to reach

Mazda_mender · 5 May 2023 04:56

ICV, autolinkmx5 as them in stock,if that one as given up, chances are the others are also the same age, personally if the budget will allow , then i would change the lot for piece of mind.
how long was she having her steam off moment for before you noticed? if she did not hit red then it sounds like it was just spraying out and venting off from then hitting hot metal , she will be fine.
M-m

ast · 5 May 2023 08:01

I would also check the fan function. The fan should have kicked in when the car was stationary, causing the car to run hot, and causing a weak hose to fail. Certainly on mine, the fan failed to kick in due to a corroded connector block which sits behind the side light, exposed to the elements for 20+ years.

I would only replace hoses with genuine Mazda, based on experience.

And also based on experience, convert to a waterless coolant, like Evans Power Cool 180. It is expensive to convert (cost me £100, with the garage splitting the prep fluid between 2 cars), but it saved me twice on an older engine (corroded fan connector block and later a stuck thermostat). Waterless coolants are touted for track cars (maintains temperature more evenly, so less loss of power over a session, in terms of MX5 track times I have seen, the evidence is convincing), but I believe there are strong benefits to older cars that are compatible (there is speculation, largely uninfomed, about effects on waterpumps. I’ve had no issues over several years). It doesn’t pressurise like water-based coolant (I can safely remove the radiator cap on a hot engine). When hoses fail, its usually pin holes, and as the coolant is pressurised, you can lose a lot of coolant quickly, and the dampened temperature gauge doesn’t give you that much warning (though the B6 and BP engines are pretty robust). Additionally, the coolant resists temperature rises (eg. blocked thermostat; I managed, with care, a 100 mile drive, with the engine, while running hot, never over heating).

That a narrow hose failed maybe indicates that the passage ways have a bit of crud, and a weak spot was found. So you probably should get the system back flushed at least.

Also worth noting, on these earlier cars, the thermostat housing hose can get blocked with swarf (the theory is cylinder head machining material gradually accumulating). That can lead to an engine running a little hot over a long time with the owner not noticing (thanks to the dampened gauge). Leading to the fan motor failing. Happened to my 91 Roadster; a series of over heating, only really diagnosed when after a radiator was replaced, a linearized (non-dampened) gauge mod revealed the car was progressively getting hot at a normal motorway cruising speed, and it wasn’t really coping with standing traffice (when the fan was supposed to help). It turned out the fan was running most of the time, because of that blocked line.

Sprint · 5 May 2023 09:34

So took another look this morning, everything has dried up, except that line, which confirms its leaking to me as water is wicking out the hole.

All i need todo is find a replacement. I’m suppose to be meeting some friends on Sunday morning and had hoped to take the MX5, but unless i can get my hands on a replacement, ideally today (out tomorrow at a coronation party), thats looking like a non-starter.

Mazda_mender · 5 May 2023 09:41

The car was not overheating ,it was spraying out and steaming off so the fan will not kick in,If you were closer to me ?
M-m

Sprint · 5 May 2023 09:54

The temp gauge was climbing rapidly while sitting idling, it was getting close to the top, but the line only split seconds after I shut the engine off, pressure was clearly building up as it got hotter.

I popped the rad cap off this morning now its cooled, and its VERY brown. Could definitely benefit from a flush?

Mazda_mender · 5 May 2023 11:16

Then she will be fine, it looks like she does a lot of sitting about, and is time to look at overhauling the cooling system completely, hoses ,rad, thermostat etc, when was the last time the water pump was done also.
M-m

Sprint · 5 May 2023 13:04

Water pump was changed in 2007 along with the radiator, and water pump was changed again in 2014.

I knew I’d run into these sort of issues, the whole reason the previous owners wanted to sell it was because it wasn’t getting the use, and with any car that sits for a while, things go brittle or age out, so I fully expect to run into issues like this, which is fine, I’d rather find them now than in August when I’m on my way to the Nürburgring, so yes, I think a whole new coolant piping kit is on the cards as well as a full flush!

Went over to Brayley Mazda in MK on my lunch hour, and the 3 lads in the parts team spent a good 20 minutes going through their diagrams, and meant that we eventually managed to identify the offending split line. Its a B61P13681B

but I think I’ll just order an entire kit!

DickieRltd · 5 May 2023 18:22

Before you just change those lines grab hold of the other hoses and give them a squeeze. If they feel crunchy replace the lot with new hoses. The ones at the back of the head are horrors to replace but woth doing while all the water is out of the engine.

ast · 5 May 2023 19:39

To be fair, heater hoses on a 1.6 are a piece of cake compared to the 1.8.

rogerzilla · 6 May 2023 14:22

The really hard one to change (I had a 1.8) is the one under the inlet manifold. The one at the back of the head on the nearside is doable with long pliers to squeeze the clip. All the rest are straightforward. Do the thermostat too - a new one can make a world of difference to how quickly the car warms up from a cold start.

david-p · 6 May 2023 15:37

I agree: a complete overhaul of the water cooling system will be a good investment.

David

Sprint · 11 May 2023 15:31

ok so new Silicone hose kit arrived about 10 minutes ago,

…but there’s a big warning on the bag, about what type of coolant to use, as not to damage the silicone hose (didn’t know that was a thing)

It references this PDF…

which I’ll be honest, just complicates the matter future.

The coolant in the car is brown, so I have no idea what’s in it now, so I think I’ll have to drain the lot. (is there a drain plug somewhere thats easy to remove?) Once drained, what should i put in thats silicone hose safe? (I have a Halfords around the corner) would this suffice?

Also, what’s the best/correct procedure to bleed the system? Fill, run, if temp climbs, shut off, fill some more, and repeat till the fans kick in? (I think that was the process for my old Subarus).

Only going to replace the failed line today to get the car on the road. Cars going into the shop for timing belt in a few weeks, will have them replace all the other lines then while they’ve got the engine in bits

All advice and tips welcome Thaankkss

(oh and I’ll overhaul the entire cooling system in due course, still broke from buying it, taxing and insuring it, only had it 11 days, which it worked for 4 of those )

ast · 11 May 2023 22:21

The drain plug is a plastic cross head plug on the bottom of the radiator that will been a JIS scfrewdriver. It strips easily. Alternatively pull the bottom hose.

Flush and backflush the system with water. Use pink or green antifreeze.

Sprint · 14 May 2023 22:28

So… update!!

I replaced the line on Thursday, then on Friday I drained the coolant. The drain valve on the bottom of the rad striped the second looked at it,

so I dropped the undertray and pulled the bottom rad hose. The water that came out was pretty grim,

I’ve refilled with distilled water and Rad flush, bled it, and everything seems fine.

Done some miles and all seems well. Still no idea WHY she overheated in the first place, the fans have been kicking on just fine…

Next weekend, I’ll drop the coolant again, and run another load of water/rad flush through, and while there, a friend is going to help me swap all the other lines over, as well as try flush out some of the blocked lines. (this is the pipe the line that failed was attached to. It pressurise (clearly as the hose attached to it split when it got hot), I couldn’t blow air through said failed hose so it too was blocked, and the replacement one doesn’t get warm even when the engines up to temp, suggesting there is little to no flow (I unblocked what i could) this is off the bottom of the Idle Control Valve. Perhaps explain why she doesn’t ideal well/smooth/is too fast?

While under there, I noticed alot of oil, on what I suspect are the powersteering lines? Something I should be concerned about?

Mazda_mender · 15 May 2023 05:40

Looks like its all been well over due…time to strip it all down and sort those oil leaks also asap, otherwise you are wasting your time, but for any of those that might hit the rad drain plug issue…and just make sure on re fitting its smeared with a lick of red rubber grease to stop it sticking but still seals…

M-m

MickAP · 15 May 2023 07:07

Clean it all up, reckon the crank seal is leaking.

Sprint · 23 May 2023 15:58

So the saga continues. Took the car up to a friends at the weekend, plan was to change silicone lines, oil, oil filter, plugs ech.

We got some hoses changed, flushed a lot of lines out, but the idle control valve is totally blocked. Then, we attempted to change the line that comes off the thermostat housing… well…

The line snapped clean off with minimal force when we tried to remove the new line.

So new thermostat housing on order, I’ve also ordered a thermostat too since its open now, as well as a new ICV
since its filled with sludge.

At least the oil change/filter went smoothly. Ended up having to get a lift home, as the car is off the road. Getting the train back up on Saturday when we’ll hopefully get all the parts swapped over.

I’ll keep you’ll posted

Mazda_mender · 24 May 2023 05:42

If that T piece is toast, chances are the L piece on the water pump inlet is to or not far behind, get that checked also.
M-m

Sprint · 24 May 2023 10:14

Once the timing belt kit arrives (on back order), I’m having the timing belt done, water pump, crank seal, the works. Issue is, I’m running out of money!! (cheap weekend toy my ■■■■ )