Do Not Sell My Personal Information Jump to content


Ls400 Water Temp Question In V Hot Weather & Jam


Recommended Posts

This happened about 2 or 3 weeks ago so I thought I had better ask what the normal might be.

The outside temp was as hot as I ever remember it, 34c on the external temp gauge. I had driven app 30 miles into London & hit a jam, it was crawl a few meters & stop for a while, this lasted for appx half hour & we travelled maybe 6 meteres in that time. I headed for a back st exit route but appx 10 mins before I got there I noticed the water temp gauge was as close to red as it gets, no idea how long it had been that close, I had the AC running all the time. Once I noticed it I stopped & started the engine only to move another few metres, that cooled once stopped & once I got out of the jam it started to go down again, it never boiled over but I was worried.

I once had a Merc190 which ran almost on red as its normal running temp all the time. I just want to know would this sort of hovering on red like that be normal for an LS 400, I never saw any of the other traffic stopped with overheating probs & the outside temp was an horrendous 34c.

Any comments as to the normality or otherwise of this guys?

Link to comment
Share on other sites


This happened about 2 or 3 weeks ago so I thought I had better ask what the normal might be.

The outside temp was as hot as I ever remember it, 34c on the external temp gauge. I had driven app 30 miles into London & hit a jam, it was crawl a few meters & stop for a while, this lasted for appx half hour & we travelled maybe 6 meteres in that time. I headed for a back st exit route but appx 10 mins before I got there I noticed the water temp gauge was as close to red as it gets, no idea how long it had been that close, I had the AC running all the time. Once I noticed it I stopped & started the engine only to move another few metres, that cooled once stopped & once I got out of the jam it started to go down again, it never boiled over but I was worried.

I once had a Merc190 which ran almost on red as its normal running temp all the time. I just want to know would this sort of hovering on red like that be normal for an LS 400, I never saw any of the other traffic stopped with overheating probs & the outside temp was an horrendous 34c.

Any comments as to the normality or otherwise of this guys?

Check the cooling fan for the engine is running at high speed when hot, fluid coupling may be faulty.

Were the fan/s running for the aircon?

Thermostat OK, coolant level Ok radiator not blocked???

Link to comment
Share on other sites

This happened about 2 or 3 weeks ago so I thought I had better ask what the normal might be.

The outside temp was as hot as I ever remember it, 34c on the external temp gauge. I had driven app 30 miles into London & hit a jam, it was crawl a few meters & stop for a while, this lasted for appx half hour & we travelled maybe 6 meteres in that time. I headed for a back st exit route but appx 10 mins before I got there I noticed the water temp gauge was as close to red as it gets, no idea how long it had been that close, I had the AC running all the time. Once I noticed it I stopped & started the engine only to move another few metres, that cooled once stopped & once I got out of the jam it started to go down again, it never boiled over but I was worried.

I once had a Merc190 which ran almost on red as its normal running temp all the time. I just want to know would this sort of hovering on red like that be normal for an LS 400, I never saw any of the other traffic stopped with overheating probs & the outside temp was an horrendous 34c.

Any comments as to the normality or otherwise of this guys?

Check the cooling fan for the engine is running at high speed when hot, fluid coupling may be faulty.

Were the fan/s running for the aircon?

Thermostat OK, coolant level Ok radiator not blocked???

I had a faulty temp gauge, actually, it turned out to be some sort of earth fault with the sender unit. The gauge would go right up to maximum, gave me a scare, because the assumption is the gauge is giving a correct reading. First time it happend was stop-go motorway traffic. I didn't initially notice it go up either, but later on I saw it moving up much quicker than a true reading could possibly move

Link to comment
Share on other sites


Check the cooling fan for the engine is running at high speed when hot, fluid coupling may be faulty.

Do you mean normal hot? to be honest I would not know what high speed fan would be.

Were the fan/s running for the aircon?

Yes but I did notice the AC was not as ice cold as it normaly is, cold but warmer than normal

Thermostat OK, coolant level Ok radiator not blocked???

Coolant level is ok but dont know how to check thermostat.

So do I take it that its not normal for it to go to slightly below red on clock? I mean it was odd in that it went just about up to it but not over & there was plenty room left for it to go over, that red mark is below the last mark, the merc ran more or less on edge of red all time & that was normal running.

Link to comment
Share on other sites


OK thanks thats all helpfull, I wish I could remember if I glanced at the gauge during the 30 mile run prior to hitting that jam, I vaguely 'think' I remember looking at it at some point but noticed nothing unusual, mine normaly runs on the one mark down from the half way mark, so did my others, pity I did take more notice that day that would give me an idea what would be normal in a no jam situation at 34c, i checked quite a bit the day after but nothing abnormal but the weather never repeated that temp

Link to comment
Share on other sites

OK thanks thats all helpfull, I wish I could remember if I glanced at the gauge during the 30 mile run prior to hitting that jam, I vaguely 'think' I remember looking at it at some point but noticed nothing unusual, mine normaly runs on the one mark down from the half way mark, so did my others, pity I did take more notice that day that would give me an idea what would be normal in a no jam situation at 34c, i checked quite a bit the day after but nothing abnormal but the weather never repeated that temp

Hi

Scenario could be a failing water pump as this happened to me about seven years ago on my 1990 ls It did exactly what yours as done ran normally for a few weeks and then failed ,fortunately there was no damage to the engine but it cost nearly a grand and a towin to fix at Lexus .Buggers up the cambelt the tensioners and they along with the water pump needed replacing.I noticed a slight change in the frequency noise coming from the front of the engine prior to this event but put it down to normal wear and tear, but it was'nt a screaming sound so it is hard to determine the cause.

It might be worth checking out this possibility.

Link to comment
Share on other sites

OK thanks thats all helpfull, I wish I could remember if I glanced at the gauge during the 30 mile run prior to hitting that jam, I vaguely 'think' I remember looking at it at some point but noticed nothing unusual, mine normaly runs on the one mark down from the half way mark, so did my others, pity I did take more notice that day that would give me an idea what would be normal in a no jam situation at 34c, i checked quite a bit the day after but nothing abnormal but the weather never repeated that temp

Hi

Scenario could be a failing water pump as this happened to me about seven years ago on my 1990 ls It did exactly what yours as done ran normally for a few weeks and then failed ,fortunately there was no damage to the engine but it cost nearly a grand and a towin to fix at Lexus .Buggers up the cambelt the tensioners and they along with the water pump needed replacing.I noticed a slight change in the frequency noise coming from the front of the engine prior to this event but put it down to normal wear and tear, but it was'nt a screaming sound so it is hard to determine the cause.

It might be worth checking out this possibility.

Hi ambermarine, I doubt its the water pump, that was changed with last cambelt change at 90k its only done 126k

It did exactly what yours as done ran normally for a few weeks and then failed

Maybe I was not clear, it was only under those conditions if being in a jam in a temp of 34c outside that there was a problem with the gauge fractionaly close to the red, when I switched off ignition it went down quite quickley (minuets) once out of the jam it went down to a non worrying level within a min or 2 of normal driveing, it never boiled over or steamed, since then its run normal but outside temp has never really gone much

above 22c at the highest since then.

Link to comment
Share on other sites

Sounds like a possible fan problem to me, anything from no signal from temp sensor to vc on the fan itself.

I had a similar problem on an old SD1 Rover many years ago, was alright normally but when in a jam on a hot day she got very hot. That was down to the vc on the fan.

I would just eliminate things one by one (obvious I know and I apologise if you are already doing this) some one on these forums will know how to check if there is a signal going to the fan etc, sorry I cant help on that. The fan check is easy enough with two people one to run the engine above idle one to watch the fan etc.

Good luck finding the culprit and if nothing else, while you're there why not give the cooling system a flush if it hasnt been done for a while and check for debris, pipes deteriorate from the inside too even if they look ok from the outside, worth a shufti.

Link to comment
Share on other sites

This happened about 2 or 3 weeks ago so I thought I had better ask what the normal might be.

The outside temp was as hot as I ever remember it, 34c on the external temp gauge. I had driven app 30 miles into London & hit a jam, it was crawl a few meters & stop for a while, this lasted for appx half hour & we travelled maybe 6 meteres in that time. I headed for a back st exit route but appx 10 mins before I got there I noticed the water temp gauge was as close to red as it gets, no idea how long it had been that close, I had the AC running all the time. Once I noticed it I stopped & started the engine only to move another few metres, that cooled once stopped & once I got out of the jam it started to go down again, it never boiled over but I was worried.

I once had a Merc190 which ran almost on red as its normal running temp all the time. I just want to know would this sort of hovering on red like that be normal for an LS 400, I never saw any of the other traffic stopped with overheating probs & the outside temp was an horrendous 34c.

Any comments as to the normality or otherwise of this guys?

I had exactly the same thing once on my old 1990 LS - sweltering day, traffic jam on motorway, A/C on. Didn't notice temp reading until moving off and hearing horrendous pinking.

I did have the radiator flushed, but that car always had a tendency to pink slightly in very humid conditions with the A/C on.

Cars for certain markets (other than the UK) had two auxiliary fans fitted instead of just the one, so clearly a known issue.

I'd say this was normal, and one of the very few design shortcomings of the early LS. Just don't have the A/C on in stationary traffic and high outside temps - it won't cope.

Link to comment
Share on other sites

If you are creeping along under the circumstances you describe, I would imagine the trans fluid would be very hot indeed.

This is cooled by the radiator so you have combined heat above average at the radiator itself

The fluid coupled fan would be at its highest speed acording to engine speed.

If it's not at peek performance this would aggravate the problem.

It has to pull air through the a/c radiator first.

Link to comment
Share on other sites

I would imagine the trans fluid would be very hot indeed.

This is cooled by the radiator so you have combined heat above average at the radiator itself

Ahhh...now you've hit on something, I had my hand out of the window & could feel a lot of excess/abnormal heat coming from somewhere below, being in the car I could not determine ecactly where but for reasons I could not pin I did not think it was the exhaust but now you mention trans fluid thats starting to paint a wider picture of things going on at the time, is the trans box below the trans stick? that area would account for the abnormal heat I felt coming up from somewhere, I also wonder if theres a final boost on the fan because at the end of the day it was fractionaly below the red & not over, what would have happended if I had not started turning it on when we moved a few metres & off wwhen that came to a standstill again I dont know, wish I knew how long it had been like that before I noticed it.

Do you think I should have turned AC off, as I said that was coolish but not cold as it normaly is when turned to cold

Link to comment
Share on other sites

I would imagine the trans fluid would be very hot indeed.

This is cooled by the radiator so you have combined heat above average at the radiator itself

Ahhh...now you've hit on something, I had my hand out of the window & could feel a lot of excess/abnormal heat coming from somewhere below, being in the car I could not determine ecactly where but for reasons I could not pin I did not think it was the exhaust but now you mention trans fluid thats starting to paint a wider picture of things going on at the time, is the trans box below the trans stick? that area would account for the abnormal heat I felt coming up from somewhere, I also wonder if theres a final boost on the fan because at the end of the day it was fractionaly below the red & not over, what would have happended if I had not started turning it on when we moved a few metres & off wwhen that came to a standstill again I dont know, wish I knew how long it had been like that before I noticed it.

Do you think I should have turned AC off, as I said that was coolish but not cold as it normaly is when turned to cold

Theoretically, I would have thought leaving the aircon with it's fan or fans [there is only one on my '94] running would help to cool things.

There would be additional air flow over everything, but this is speculation on my part...

Link to comment
Share on other sites

If it happens again, turn the cabin heater up to full temperature, on full blast. That'll remove some heat from the equation.

Unfortunate advice I think ,we have been informed outside tempratures were 34 so the solution to the problem is make it really hot in the cabin and apart from the driver and passengers collapsing from heat exhaustion the engine will be fine.

The advice given dates back to cars that did'nt have air con and ran rudimentary heating systems and by turning the heat up in the cabin you would take water from the engine to the heater matrix therefore widening the dissapation of the water temprature.

We are getting away from the fact that Lexus have built a very highly engineered climate control system and a finely tuned and engineered gearbox and engine which as been built to perform in far more hotter climates than we have in the UK including the middle east which gets desert hot.

So if you are to have peace of mind on what caused this phenomenom I would get the relevant systems checked out before it turns into a big bill.

Link to comment
Share on other sites

Well guys I think you've all helped me get an answer, which seems to be. The AC is not a lexus AC I dont know what make it is but the last owner changed the lex to another, this one, I did not know till know ac had any connection to rest of stuff we talked about here it all runs normal, in fact the engine & transmission are A1, that is untill I ran into this extreme half hour so I need to change it back to lex. Thanks, any comments

Link to comment
Share on other sites

My 96 400 would actually run very slightly cooler "on the gauge" when stationary or in slow traffic.....the big viscous fan is so over engineered....AC on or off...

Good Luck with sorting it. ;)

Link to comment
Share on other sites

Unfortunate advice I think ,we have been informed outside tempratures were 34 so the solution to the problem is make it really hot in the cabin and apart from the driver and passengers collapsing from heat exhaustion the engine will be fine.

The advice given dates back to cars that did'nt have air con and ran rudimentary heating systems and by turning the heat up in the cabin you would take water from the engine to the heater matrix therefore widening the dissapation of the water temprature.

We are getting away from the fact that Lexus have built a very highly engineered climate control system and a finely tuned and engineered gearbox and engine which as been built to perform in far more hotter climates than we have in the UK including the middle east which gets desert hot.

So if you are to have peace of mind on what caused this phenomenom I would get the relevant systems checked out before it turns into a big bill.

I very much doubt anyone would collapse from heat exhaustion, that's why we have windows which can open. Simply put, if the coolant looks like it might be getting a bit on the hot side, a way of reducing its temperature is simply to blast some of that heat out the vents inside the car. Lexus might have designed a nice AC system but to heat the interior it'll still use heat from the engine's coolant.

It isn't a solution, just a stop-gap measure to reduce any potential damage until the problem is fixed. You'd be surprised how effectively it can reduce coolant temperatures.

Link to comment
Share on other sites

The A/C system essentially has three parts - condensor, pump and evaporator. The evaporator communicates with the car's interior, and the condensor with the outside world. As air is blown over the evaporator (to cool the car's interior), the refrigerant will pick up heat. That heat is deposited (via the condensor) right in front of the main radiator. So, on a hot day with the A/C on, you will be blasting hot air right onto the rad. Not ideal! In stationary traffic, without forward movement to assist in the throughput of fresh air, it is to be expected that the coolant temperature will rise. It is so rare to experience high outside temps in the UK that Toyota specified only one electric fan for this market. Versions for hotter climates (and later models?) had two fans. If the engine is overheating, turn the A/C OFF and the heater ON.

Link to comment
Share on other sites

Has anyone retro fitted a second fan, and if so, how easy was it? Thinking about doing this myself so hoping it isn't wildly expensive or difficult.

Link to comment
Share on other sites

The A/C system essentially has three parts - condensor, pump and evaporator. The evaporator communicates with the car's interior, and the condensor with the outside world. As air is blown over the evaporator (to cool the car's interior), the refrigerant will pick up heat. That heat is deposited (via the condensor) right in front of the main radiator. So, on a hot day with the A/C on, you will be blasting hot air right onto the rad. Not ideal! In stationary traffic, without forward movement to assist in the throughput of fresh air, it is to be expected that the coolant temperature will rise. It is so rare to experience high outside temps in the UK that Toyota specified only one electric fan for this market. Versions for hotter climates (and later models?) had two fans. If the engine is overheating, turn the A/C OFF and the heater ON.

That makes sense, so does a second fan but the thing is I have never had it or any problems since & it seems unlikely we'll get that temp in a jam very rarely, would taking it out of gear make any differnece whilst waiting, that transmission was very hot I think. Could even stop it a few times if it seemed like a long jam.

Link to comment
Share on other sites

Has anyone retro fitted a second fan, and if so, how easy was it? Thinking about doing this myself so hoping it isn't wildly expensive or difficult.

I think series one cars had two electric fans, you might get the whole shroud complete with fans

from Benfur [this club] or Ebay..

Link to comment
Share on other sites

Has anyone retro fitted a second fan, and if so, how easy was it? Thinking about doing this myself so hoping it isn't wildly expensive or difficult.

I think series one cars had two electric fans, you might get the whole shroud complete with fans

from Benfur [this club] or Ebay..

Thanks for that, I will investigate, cheers.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...




Forums


News


Membership