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Another overheating LS400 problem!

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Old 06-27-09, 12:53 PM   #1
zaphod
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Default Another overheating LS400 problem!

Yes, I have done a search here, too. I've been a bit of a long time lerker!

Car is a 1992 LS400 141k miles (today!)

Here's the story

Symptoms of overheating first came about around 2 or more months ago. 35 mile trip down the A roads to Priddy, Somerset via Cheddar Gorge. Coolish day, damp and some heavy rain. Climbing up the Gorge - it is twisty and steep in some parts, got stuck behind a van that was struggling, slow around 10mph, and those tight bends. Temperature Gauge shot up to H. Once on the flat the gauge quickly returned to its normal reading. Trip back home was uneventful. Topped up the coolant, which was low. I regularly and frequently check levels, BTW. Thought nothing more of it.

3 weeks ago trip 8 mile trip down to the City Centre - really a clear run along country lanes and a dual carriageway - about 3 miles into the journey. Gauge shoots up to H, and stays there or there abouts until I pull in, when it drops rapidly to normal. Again, journey home uneventful.

Intalled a new thremostat, after all it cannot do any harm anyway, and the symptoms above seemed to suggest this. Did this Tuesday last. Have been driving to work and back a 10 mile journey everyday - sometimes twice - no issues.

So to today.

Bristol to Bampton - around 75 miles there and 75 back, mostly M5. I am not heavy right-footed and usually cruise around 65-70 mph (The Lexus is that sort of drive for me !)

No problem for 55 miles, then stop/slow in traffic very briefly for no more than 3 minutes - really crawling as drivers on our carriageway were rubbernecking an over-turned caravan on the other. Gauge went up to H and stayed there.
Pulled in when it was obvious it was not going to fall back - as it had done in every instance. Let the car cool down. Very little water - here's the thing although I have been replenishing coolant/water - I have never seen the car, or had evidence of the car physically dumping loosing coolant (ie a puddle).

There was steam coming from the Top Left Hand cylinder bank, not in great amounts, but escaping nonetheless. Waited for the car to cool down a little then replenished with water, with the car running, for around 10 minutes until the level stayed constant.

The car - when started from hot always has a tendency to badly misfire and almost stall in summer weather - and did so again at this time. Would a gone head gasket and escaping electrics affect HT leads and plugs (Sorry - I am new to Lexus, being familiar with Saabs).

2 mile drive to my daughters - no issues. Checked coolant - it was as was. A bit of a rattle from the front of the car, which soon disappeared. I know these things do not disappear never to come back again, and having listened to the idler pulley with a screwdriver, which appears to be the culprit)
Time to drive back to Bristol. Double check coolant. Fine. 8 miles into the drive - country lanes gauge climbs back to H for around 2 minutes, and then drops down rapidly - as it does - to its normal reading. The rest of the journey 60-odd miles along the M5 home was uneventful. I haven't checked to see if there is a pool yet, or if the coolant has all but disappeared again, but neither would surprise me.

What is making me rather suspicious that something went on with the car before I bought it, and I suspect before the person I bought it from, (he is a good and very trustworthy friend) as the low coolant light never shows on the dashboard, as a warning except at start-up - so I wonder why this has been disconnected?????

Is there a way of servicing the switch in the expansion tank - it seems a sealed unit to me?

So, what is the concensus?
  • Water Pump (How long do they last)?
  • Head Gasket - Left Hand Bank?
  • Failed Hose - which one's the favourite?
  • Radiator Flush (on my list to do's in anycase)?




And of course, where has the water gone?

Any help, wise words of wisdom or experience will be gratefully appreciated, and please pose further questions that I can answer to help find a resolution.
I am here to learn more about myLexus, as Workshop Manuals apart from pirated ones are few and far between, here! We all have to start somewhere!

Thanks.
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Last edited by zaphod; 06-27-09 at 01:02 PM..
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Old 06-27-09, 05:11 PM   #2
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sounds like either the WP is dying OR more likely there is/was a BIG bubble in your cooling system and you need to burp it.
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Old 06-27-09, 06:01 PM   #3
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If there was steam obviously theres a leak in the system in that vicinity. Did the steam smell like coolant? The coolant might be leaking out and evaporating as soon as it hits the engine. On your last oil change did you notice any coolant in the oil?
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Old 06-27-09, 07:56 PM   #4
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its not ur waterpump dying, they either leak or the bearings fail, the impellor inside isnt broken or u would have no circulation what so ever and it would overheat immediately..there is an oring on the expansion tank sensor....sounds like an air bubble to me
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Old 06-27-09, 09:18 PM   #5
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If you're sure you saw steam, then its surely a leak. Also when engine cools down it might be sucking in air from the leak location. Do they have a UV dye for coolants?
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Old 06-27-09, 10:12 PM   #6
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shouldnt need one with the toyota red
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Old 06-28-09, 04:06 AM   #7
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Thanks for the replies so far, everyone.

Once again when I checked last night, no water left in the expansion tank. No sign of where it has gone. The only sign of a coolant loss was the steam small amount by from the offside bank, yesterday, as above.

The steam did smell of coolant. Is there another bleed hole other than the one by the thermostat? This was open when I initially filled up after replacing the thermostat, and spent 10 minutes or so replenishing while running the car to normal temperatures. I am getting the impression that clearing an airlock is a right pain - if it is that - on these engines.

I forgot to add there is a rattle at the front of the car, which when I have checked listening with a screwdriver appears to be the idler pulley - this appears to be intermittent. There was additional noise - rather worrying at the time of coolant fill up - which I put down to the car being very hot. A warning light did show just before I initially puled in, as above. The additional noise disappeared a couple or so hours by the time I had left my daughter's - the car had cooled down considerably, and did not return, even after the journey home - as I said a 70 odd mile journey home.

No water in the oil at the filler cap or dipstick. Oil appears fine.
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Old 06-28-09, 07:51 AM   #8
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take ur car to a shop and have the system pressure checked for leaks...
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Old 06-28-09, 08:19 AM   #9
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Hmm. Can do that my self with a cut bicycle inner tube, a pump and two jubilee clips. Haven't done that for years on a vehilce, tbh.

Just been out - removed the thermostat bleed screw again, and replenished around 2 or 3 litres of water this time, and let the bubles come through until the car reached operating temperature, and no more were apparent. Gave the car around 2k revs during this. Replaced bleed screw once water only came though that - no bubbles. We'll see what happens next week.

Pulley making more of a racket - will need to replace pdq.

Last edited by zaphod; 06-28-09 at 12:32 PM..
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Old 06-28-09, 05:13 PM   #10
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Fix that leak wherever its coming from.
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Old 06-30-09, 03:03 AM   #11
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Dont the early LS's get a common leak in the bottom of the overflow/topup tank? Around some sensor? Sounds like this might be it.
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Old 03-20-12, 08:36 AM   #12
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Exclamation Hope this helps!


I am having over heating issues too... Getting really over looking for problems the issue.
so far I have replaced the water pump, thermostat, top hose, Rad cap, Fan, thermostat housing, re-circulation hose, reverse flushed the rad and block.

It will get to operating temp then sit there for 10-15 min then over heat spitting coolant out the left hand side. I had thought that it could of just been the boil over hose on the over flow tank but I will pay it closer attention tomorrow.

Things I have noticed...
Small intermittent puffs of white smoke (not dissimilar to cold start on a cool morning got me thinking maybe head gasket. But I can not hear any of the tell tail "pufft" sounds that come with it. Maybe it's just to the water jacket... but some how don't think it is.)

Top hose gets really hard and hot.
Bottom hose get hard too but not as hard or as hot.
Only half the radiator gets hot (I am running a 14 inch electric fan tho)

I am now looking at the rad core if it's blocked... Will know by tomorrow whats up and will keep you all posted as your problem sounds close to mine.

And as for secondary bleeder points I know that the 2UZFE has a second bleeder halfway down the block (managed to sneak a look at the official Toyota 2UZFE workshop repair and trouble shooting manual) Maybe the 1UZFE is the same if not, look along your firewall there are 2 hoses that run from the block to the heater core, try purging from there. I know trying to get all the air out after I did the WP was a pain in the @$$.

Can't wait to get mine on the road.

Sounds like your getting loads more miles under your tread then me tho before yours shows it's ugly head. Let us know if you fix it what is was.

I'll try posting picks of mine if I figure it out and fix it with a step by step later.

Mine seems mine has most of the 1990 ls400 faults If there is a compiled list out there some direction to find it would be sweet. Cheers Mate~!
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Old 03-20-12, 12:18 PM   #13
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Here's my take on OP's issue.

If your temp gauge goes to H, your system will be overpressurized and push coolant out the overflow. Then when your system cools down, it sucks what's in the reservoir into the system causing coolant level to become low.

Also, erratic changes in temp gauge means there are air bubbles in your system, it needs to be burped.

Driving at low speeds or idle causes this is most likely a problem in the radiator. Either it is not flowing well, need to be flushed or the fans are not coming on.
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Old 03-20-12, 01:59 PM   #14
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just thinking out loud....... could you have a faulty temp sensor,, also? but be sure to burp the bubbles out, if nothing else park on a hill with the front of the engine up.. also you dont need to remove the bleed screw, just loosen it and watch for bubbles, when they stop, tighten it up.
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