She's runnin too hot !?

Lads i had a problem last year with the crank pulley slipping causing the car to seriously overheat and cut out.

my mechanic sourced a replacement from a scrapped GS300 but anyway...

my isssue at the moment is that the temp guage still has a tendancy to creep north of 90 degrees....

its getting way to close to hitting the 100 mark for me to ignore it ( actually goes upto 110 when the engine is off after a motorway run ), is there a fault i should be looking for or should i be considering making mods such as fitting a bigger rad, vented bonnet...or ?

thanks for any help.

Have you checked the coolant, is the rad full, is the expansion tank

approx half full when cold, does your heater blow hot air ?

How often was it run before you fixed it from overheating last time ?

My concern would be if it got too hot then it could have caused head

or head gasket issues that show up later.

Fitting a vented bonnet wont make any difference nor a bigger rad.

The car comes with a more than adequate cooling system in its

o/e form and unless there is a fault in that system or you have

seriously modded the engine and its running big hp single turbo

then it should be fine

thanks dunk,

coolant level is ok and i keep the rad topped up...

ill have to take a look at the expansion tank now that you mention it.

heater works fine.

if i am being honest i didnt react quick enough when it overheated last year and drove it home .

mechanic struggled to get it running at 90 and just told me to keep an eye on it ( not very reassuring ) but it seemed to settle down.

would a head gasket issue have presented itself worse by now ?

its a 1997 TT 6 speed RZ

stock turbos.

hks full exhaust system

hks air intake

hks blowoff valve

autobahn 88 intercooler

Have you checked the coolant, is the rad full, is the expansion tank

approx half full when cold, does your heater blow hot air ?

 

How often was it run before you fixed it from overheating last time ?

My concern would be if it got too hot then it could have caused head

or head gasket issues that show up later.

 

Fitting a vented bonnet wont make any difference nor a bigger rad.

 

The car comes with a more than adequate cooling system in its

o/e form and unless there is a fault in that system or you have

seriously modded the engine and its running big hp single turbo

then it should be fine

thanks dunk,

 

coolant level is ok and i keep the rad topped up...

 

ill have to take a look at the expansion tank now that you mention it.

heater works fine.

 

if i am being honest i didnt react quick enough when it overheated last year and drove it home .

 

mechanic struggled to get it running at 90 and just told me to keep an eye on it ( not very reassuring ) but it seemed to settle down.

 

would a head gasket issue have presented itself worse by now ?

 

its a 1997 TT 6 speed RZ

 

stock turbos.

hks full exhaust system

hks air intake

hks blowoff valve

autobahn 88 intercooler

With the setup you have the stock cooling system is fine.

You say your topping the rad up ? you shouldn't have to do this, this

is what the expansion tank is for.

When the car gets to normal running temp coolant is forced into the expansion tank, when it cools its drawn back from the expansion tank

into the rad so the rad should always be full as long as there's coolant in the expansion tank.

You could have a faulty rad cap so i'd start with that and replace with a

new O/E Toyota one.

I didn't like the occasional temp rise on mine after fitting a FMIC - my solution was a Fluidyne uprated Aluminium rad. No issues thereafter with lots of drag abuse in Summer.

Cheers,

Brian.

Fitting an expansion tank is something I really need to get round to doing although ive never had to top my rad up and my engine gets HOT!! Rads always full.

The stock rad if in good condition is perfectly up to the job of

cooling the mkiv TT, i have an R spec FMIC infront of mine and

have no issues even in the summer.

My rad has been replaced with a new O/E rad though.

The stock system is designed to use with an expansion tank, if

the coolant heats up and expands and is forced out the rad cap

where does it go if you don't have the tank and how can it be

drawn back in when the coolant cools ?

Perhaps your not running a stock rad cap and using a higher

pressure cap thus it's not losing coolant but is putting the whole

cooling system under higher pressure which isn't such a good idea.

The stock rad if in good condition is perfectly up to the job of cooling the mkiv TT, i

have an R spec FMIC infront of mine and have no issues even in the summer.

My rad has been replaced with a new O/E rad though.

 

The stock system is designed to use with an expansion tank, if your coolant

heats up and expands and is forced out the rad cap where does it go if you

don't have the tank and how can it be drawn back in ?

 

Perhaps your not running the stock rad cap and using a higher pressure cap thus

its not losing coolant but is putting the whole cooling system under higher pressure

which isn't such a good idea.

I have an SRD rad but im not sure what the cap tempreture is on these.

I have an SRD rad but im not sure what the cap tempreture is on these.

The caps are rated on their pressure, when they reach their rated pressure they

release coolant to the expansion tank.

The higher the pressure cap the hotter the coolant can get before its released.

Aren't the SRD rad's also designed to use an expansion tank?

The caps are rated on their pressure, when they reach their rated pressure they

release coolant to the expansion tank.

 

The higher the pressure cap the hotter the coolant can get before its released.

Ah ok then. It does seem to get very hot under the bonnet especially being single an all. I will have to hurry and get a proper temp gauge fitted as the stock gauge is always on half way once driving for 5 minutes and is not very accurate.

With the setup you have the stock cooling system is fine.

 

You say your topping the rad up ? you shouldn't have to do this, this

is what the expansion tank is for.

 

When the car gets to normal running temp coolant is forced into the expansion tank, when it cools its drawn back from the expansion tank

into the rad so the rad should always be full as long as there's coolant in the expansion tank.

 

You could have a faulty rad cap so i'd start with that and replace with a

new O/E Toyota one.

funny you should mention the rad cap, i had to replace it last year not long after the overheating issue.

the cap actually came apart ! having unscrewed the cap i found the inner part still sat in the rad with the flat cap in my hand.

i got a replacement from a regular motor factors..rated at 1.2 bar , i think the original was 1.1

so you reckon the aluminium rad would just be a waste of money ? i seen tDR saying it helped...am confused now ! lol

I would say you may have head gasket issues. If it got mad hot it's probably warped the head, maybe even softened the alloy material itself. Needs a combustion gasses in the coolant test performed and a pressure rise check done. Any decent garage can do both. If the heads warped it's probably scrap.

If the cooling system hasn't been bled properly, it could cause the issues you are experiencing with intermittent air blocks.

If the cooling system hasn't been bled properly, it could cause the issues you are experiencing with intermittent air blocks.

^^ yeah that. Mine was a bit of a pain to bleed through after changing the rad.

As Chris points out, it's well worth doing the diagnostic tests as a first port of call if your car has already had a proper roasting as the heat could have warped the mating face on the head allowing hot combustion gases into the Cooling system (sniffer test shows this) or Oil (creamy mayo like substance under the rad cap shows that).

From my POV the standard rad was not up to the job with what is effectively a massive airflow blockage in front of it in the form of a Front Mount Intercooler. That was at strong BPU power levels on the strip.

A brand new OEM rad may be more up to the job than an old one but neither were designed with reduced frontal airflow in mind - a Fluidyne or similar uprated rad makes a now marginal Cooling situation safer IMO.

As Chris points out, it's well worth doing the diagnostic tests as a first port of call if your car has already had a proper roasting as the heat could have warped the mating face on the head allowing hot combustion gases into the Cooling system (sniffer test shows this) or Oil (creamy mayo like substance under the rad cap shows

Is it not the oil cap where the mayo substance would appear not the rad cap?

Sometimes one or the other, sometimes both. Sniffer test, dye test, pressure rise test in combination should be pretty conclusive. Without the right gear you are wasting your time, and the proper tests won't be very dear.

Am I right in saying running the car without the expansion or rad cap off will push out any air blocks?

As I did this on a V12 BMW engine with the same symptoms just as I thought in theory this would make sense. It cured it so must have been an air block.

Edit: By running I mean revving it slightly with the bonnet up then slowly tightening the caps back up. Not driving it about lol.

Also I can't remember if it was the rad cap or expansion cap. Sure it was expansion cap

Sometimes one or the other, sometimes both. Sniffer test, dye test, pressure rise test in combination should be pretty conclusive. Without the right gear you are wasting your time, and the proper tests won't be very dear.

Pissing in the wind is the term I believe. If i could diagnose a car from the other side of a computer screen, I'd be a very rich man!

Mr Wilson is the man. Listen to him and you won't go far wrong.

funny you should mention the rad cap, i had to replace it last year not long after the overheating issue.

 

the cap actually came apart ! having unscrewed the cap i found the inner part still sat in the rad with the flat cap in my hand.

i got a replacement from a regular motor factors..rated at 1.2 bar , i think the original was 1.1

 

so you reckon the aluminium rad would just be a waste of money ? i seen tDR saying it helped...am confused now ! lol

I can only go on my experience with my car which is the OE rad works fine if in good

condition, there are guys on here running single turbos with the OE rad so bpu should

be a doddle.

As i said in my first reply perhaps the previous overheating has damaged the head and

or head gasket.

A sniff test is definitely a good idea along with a pressure test.

People seem to think bleeding the cooling system is difficult on the MKIV, and it is NOT. Just idle the engine with the radiator cap off, and keep topping up the coolant level as it drops. If there's a lot of air in it there may be a time when it vents coolant and belches and farts water and steam for while. Just keep the hot coolant off yourself and just keep topping. Unless something dire is amiss it'll settle. Do all this with the heater set to max temp. That's it.... Check rad level after it's cooled after a short run and make sure the overflow reservior is up to its level mark. DO NOT fit a higher pressure cap unless you like to play Russian Roulette. Tired heater matrices will NOT like another few PSI in them, and there's no need to try to raise the coolant boiling temp over the stock figure. High pressure caps are for very specialist usage. Nor will a "cool" thermostat help an engine that has "issues". It'll just drink fuel and contaminate the engine oil with condensation. A "cool" `stat is also for VERY specialised usage on engines with mappable ecus, where you KNOW the engine is off the cold start map even when the coolant is silly cool. You'll get more performance gain from putting a few more PSI in the tyres than fiddling with funny thermostats.

Some people also run those same Single Turbo cars at low boost / off boost 99% of the time, never partake in anything remotely Motorsport related and / or just polish up their shiny shiny under the bonnets rather than take their cars out and give them a properly good spanking frequently.

Thinking it through though, a BPU car generates a lot of heat by virtue of it's small and increasingly ineffecient Turbos - the higher the boost, the truer this becomes. The same is not necessarily true for the Single Turbo cars.

It also depends on the traffic scenarios you find yourself in just how well a car with an FMIC will cope RE: the cooling system.

Well i guess we could go on for ever with this

I don't doubt your new Fluidyne rad does the job on your car or you wouldn't be saying so

but in the same breath i've done trackdays in my car and not suffered my coolant

getting hotter than normal.

I've never had a problem in slow moving traffic or any other variant that you can

think of that's raised my coolant temp.

Were going a bit away from the op's problem now though as he really needs to do

some simple tests to see whats the cause of his overheating problem, i just started

with the simple cheap fix first

Agreed, diagnostic tests are the best way forward.

RE: being on topic: The OP also asked about uprated Radiators, amongst other things, to which you offered the view that the standard Radiator was fine with his spec. I noticed the 'Autobahn 88 Intercooler' listed in his spec list and offered the opposing view that a standard ~15yr+ old Radiator (in most cases) is somewhat marginal in that configuration, as evidenced by my own experiences.

IMO, if you're replacing the Radiator and are running increased boost over stock, you are as well going with an uprated item with a larger coolant capacity, increased fin count and metal rather than plastic end tanks which in the case of many Toyotas of the era tend to go green and brittle before failing with age. Running a FMIC tends to show weaknesses with aged Radiators. Yes, a stock new replacement may keep the temp gauge in the right place but it's the same argument RE: stock or uprated when doing anything with these cars and in this case there's not much of a cost differential.

I think the very act of replacing the rad - done properly - sees a cooling performance increase as it should include a Coolant flush / replace, new thermostat and new rad cap.

All on topic and useful information for other members now and for future searches.