Temp Guage problem

[stevie_b]

Hmm, I'll need to look at my supra to get my head around what's going on with that overflow tube. I can do that tonight. From my very hazy memory, I think the standard connections should be a veritcal tube running down inside the expansion tank, and this is joined at the cap to another tube that runs horizontally into the top of the radiator. As I said, that's from memory so I might be incorrect.

 

It sounds like the overflow tube is all wrong. Coolant is pushed around the cooling system by the water pump which is driven by the cambelt (it is on most cars anyway, I assume the supra is the same). The cambelt's speed is governed by the engine revs, so when you rev the engine you speed up the water pump. That kind of explains why the rate of loss increased when you revved the engine, but the loss shouldn't be happening at all. *If* the supra is supposed to have an overflow pipe, I would expect it only to come into play when the cooling system is about to burst due to excess pressure.

 

If I'm home in time tonight I'll take photos of mine and post them up.

Edited April 8, 2010 by stevie_b (see edit history)

[SteveR]

Change the radiator cap, the spring has probably gone - at least that is the most likely cause at the moment. They are only ~£10 brand new but you could end up spending a lot more if you drive without enough coolant.

[adam1983]

It will be going into the garage tomorrow to get checked properly so hopefully wont come back anything bad.

 

Wont hurt getting a new rad cap anyways just to be on the safe side as they are not expensive.

Can you get these from halfords for the supra or am i better off going to toyota for one?

Only reason i say halfords is because the nearest toyota garage is quite a distance away from where i work.

Shame i dont work in nottingham because this would make things a lot more simple.

[SteveR]

I don't think Halfords do them. Give Toyota a call, they can post parts out.

[adam1983]

Does anyone know the part number for a new rad cap for a j spec 94 tt?

[stevie_b]

I've had a look at my supra this evening: the pipe from the expansion tank cap goes straight to the radiator just under the rad cap.

 

There is a drain pipe that goes through the engine undertray to the floor, but all it does is drain the battery tray of any standing water (see 2nd pic, you can see the small hole in the tray and the tube underneath).

 

Unless I'm mistaken, the cooling system doesn't have a drain/overflow tube that dumps coolant outside the system, otherwise it wouldn't be able to hold much/any pressure.

 

It won't do any harm to change your rad cap, but it sounds like there's something very wrong with how your coolant tubes are connected up. Even if your current rad cap isn't holding pressure, it shouldn't cause coolant to come out of anywhere other than the rad cap itself. It's just possible that this set-up is due to the aftermarket expansion bottle, but if so it's new on me.

[SteveR]

Unless I'm mistaken, the cooling system doesn't have a drain/overflow tube that dumps coolant outside the system, otherwise it wouldn't be able to hold much/any pressure.

You're mistaken. Looking at your photos, you're missing a tube that comes off the other side of the expansion bottle cap.

 

Coolant won't just flow away, through the expansion bottle, because the system is closed by the sprung-loaded radiator cap (assuming it's not fooked) and only opens to allow flow between the rad cap and expansion bottle (note: expansion, not a reservior like you get on most other cars) when it's fully up to temp. The overflow tube is there for if there coolant system has been overfilled, or a more serious overheating issue arises.

[adam1983]

I've had a look at my supra this evening: the pipe from the expansion tank cap goes straight to the radiator just under the rad cap.

 

There is a drain pipe that goes through the engine undertray to the floor, but all it does is drain the battery tray of any standing water (see 2nd pic, you can see the small hole in the tray and the tube underneath).

 

Unless I'm mistaken, the cooling system doesn't have a drain/overflow tube that dumps coolant outside the system, otherwise it wouldn't be able to hold much/any pressure.

 

It won't do any harm to change your rad cap, but it sounds like there's something very wrong with how your coolant tubes are connected up. Even if your current rad cap isn't holding pressure, it shouldn't cause coolant to come out of anywhere other than the rad cap itself. It's just possible that this set-up is due to the aftermarket expansion bottle, but if so it's new on me.

 

Cheers for taking the pictures,

 

my system is set up differently to yours. I will have to describe this best i can though as i dont have my camera on me until the weekend. Basically i have the radiator cap obviously on the radiator with a pipe coming off of this to the expansion tank which for me is just to the right of the radiator next to the battery. On top of the expansion tank is the cap with the hose that goes into it and also coming off of that cap is a hose that splits off that just dangles to the right of the expansion tank.

 

Hopefully that makes sense without any pictures.

 

As far as i was aware that was the correct setup but im not sure now after seeing your pictures.

 

I dont think it matters too much where the expansion tank is located though but i was under the impression that the cap on top of the expansion tank had one going into the tank with a pipe that goes off towards the actual radiator itself and one that hangs out the side too for overflow.

 

Hopefully the garage i go to tomorrow will be able to sort things out

[SteveR]

There are at least two locations the expansion bottles were fitted, and they might be different shapes as a result but here is a pic of a bottle showing both tubes:

[SteveR]

...i was under the impression that the cap on top of the expansion tank had one going into the tank with a pipe that goes off towards the actual radiator itself and one that hangs out the side too for overflow.

 

That's correct.

[SteveR]

--->>> read this

[adam1983]

So just to get this straight then, if the rad cap was faulty then it could be just going straight out the overflow pipe?

 

I havent seen any coming from the actual rad cap itself when i was revving the engine but not sure if it would be that obvious or not.

 

If they do a pressure test tomorrow would it highlight the rad cap as the fault if it was at fault?

[SteveR]

So just to get this straight then, if the rad cap was faulty then it could be just going straight out the overflow pipe?

 

I havent seen any coming from the actual rad cap itself when i was revving the engine but not sure if it would be that obvious or not.

 

If they do a pressure test tomorrow would it highlight the rad cap as the fault if it was at fault?

Have a read of the thread I linked to.

 

In essence, the spring inside the rad cap holds the coolant in the system until the pressure gets to 0.9bar (TRD caps hold the pressure to 1.1bar - don't be tempted to fit one though as they just put extra pressure on the rad, the heater matrix, etc).

 

At 0.9 bar the rad cap pring is pushed back and coolant can now get to and from the expansion bottle. The bottle is quite large so unless it was overfilled then it can easily contain the amount of fluid coming its way when the engine gets up to temp. When the car cools down, the coolant contracts, and the 'extra' gets sucked back in, the pressure drops and the spring then closes.

 

However, if for some reason the pressure gets VERY high, or the expansion bottle has been overfilled or the spring in the rad cap is past its best, then coolant will flow into the expansion bottle, fuill it up, the flow out of the expansion bottle overflow. No fluid can get to open air direct from the rad cap itself.

 

What pressure test are they doing? Pressurising the coolant system? I'm not sure how you're do that but if it onvolves takig the rad cap off then it won't show any fault in the rad cap of course. Just get a new rad cap and eliminate that from your enquiry. Paying a garage is going to get costly, quickly: it could just be a £10 rad cap!

Edited April 8, 2010 by SteveR (see edit history)

[SteveR]

stevie_b - here is apic showing the overflow pipe you're missing:

 

[stevie_b]

SteveR: thanks for the info, that's a revelation to me! . It sounds like I've got a little investigating of my own to do.

 

There's no redundant connection on my expansion cap bottle: I've only got the tube inside the bottle itself, and the single external tube you can see in my photos going from it to the rad.

 

Either Toyota changed the design of the system at some point, or I'm the one who has a peculiar set-up. It's never caused me problems in 4-5 years of ownership, but I like to know what's what on my cars.

[SteveR]

That's wierd. I wasn't aware of a type of expansion bottle without an overflow. So on yours, that nossle on the expansion bottle cap, opposite the side fitted the with the tube to the rad cap, isn't a nossle? Ju-ju.

[Swampy442]

IIRC the Soarer bottle doesnt have an overflow tube, maybe a previous owner swapped it out?

[stevie_b]

So on yours, that nossle on the expansion bottle cap, opposite the side fitted the with the tube to the rad cap, isn't a nossle? Ju-ju.

Hmm, I know what you mean. I'll have to have another look: from the pic it looks like it is a nozzle that's been plugged. From memory I don't recall seeing a plug, but that might be because I'm too used to seeing it like it is and I'm ignoring what's right under my nose.

 

IIRC the Soarer bottle doesnt have an overflow tube, maybe a previous owner swapped it out?

That's certainly a possibility. I'll take a look over the weekend. SteveR might have a point in that mine does have the 2nd nozzle, but it's been capped off with a bung.

[adam1983]

Well the car got put in the garage this morning and explained it to him.

He said he would do a pressure test and a chemical test so just waiting for the call back.

Keeping my fingers crossed its not head gasket but we will see. If it is hgf then i will be absolutely gutted but im hoping for the best

[marc_p]

I've not had an overflow pipe on either of my Supra's

[adam1983]

Got an update for you guys. Got a call from the garage and good news is that its not hgf.

They told me the viscous fan (sorry for spelling if not correct) is not coming on when its meant to so obviously building up the pressure.

Need to get a new one from toyota which is not cheap but not as expensive as it could have been.

 

Thanks for all the help from everyone on here and i will let you know how i get on once its on and working

[Swampy442]

Viscous fans dont 'come on' as such but the fluid inside does degrade with age. Just get a second hand one from Keron or anybody on here. Im sure the price of one new would make your eyes water!

[stevie_b]

Thanks for updating us Adam: let us know how it goes when you've got a new fan installed.

[adam1983]

Viscous fans dont 'come on' as such but the fluid inside does degrade with age. Just get a second hand one from Keron or anybody on here. Im sure the price of one new would make your eyes water!

 

The guy at the garage was saying it would cost about £200 from toyota but i will see if i can get one from them a bit cheaper.

Might be worth giving keron a call too as he has helped me out with parts in the past too and not too far away from me once im home.

[adam1983]

Got it sorted yesterday afternoon by paul at whiffbitz. Turns out it was the viscous fan coupling which had worn.

Got another one on now and all is working fine. Before the fan was coming on but wasnt going any faster than when the car was idling so at higher speeds it was worse.

Sorted now though so all seems to be working fine