Tribeca coolant system bleeding

[Brom55]

Hi all,

A strange request maybe,but after having a new thermostat (OEM from US ), the temp on my Tribeca is wondering near to the limit mark of normal range,(just before the red zone).

Garage did the work and have since checked stat was opening which was confirmed,and replaced with another stat to check if any improvement,but not really made any difference as temp still above half way, which was the normal temp prior to the new stats.

Engine was replaced due to original HG issues and current engine only done 40k so unlikely to be another HG issues.

I feel maybe the coolant system may need bleeding as only thing I can think of.

Any special procedures or advice taken.

(unless anyone close to Chesterfield,Derbyshire has knowledge to come and show me ).

Thanks in advance.

 

[Siluro]

Good luck I do know that Scooby's can be a pain to bleed. Fill slowly and bleed from highest point, if EJ turbo that not from the radiator cap. Even the dealerships do not know this basic procedure. Always bleed from highest point.

[Brom55]

Apologies for late post back.

Still no joy with my Tribeca, i've done the following.. and it is still overheating according to the gauge which goes 2 segments over the half way, but will drop t down to half intermittently.

*Had the oem thermostat removed, checked and replaced, coolant re-filled gently and bled, but temp still over heating

*Done multiple attempts at bleeding air using the no spill funnel kit, no changes, still over heating,

*Coolant was again drained and vacuum filled but no change last week from above heat issue

*today i have done the HG test with the Block fluid test and it was a negative result, so HG seems ok.

*Re-burped coolant on tick over with fans running, and then did 10ml drive locally.

On getting home i noticed the rad cap was barely warm, ( top hose was hot), 

I decided to gently remove the rad cap even though i had just driven the car, ( i know that isn't generally a good idea), but my thought was if rad cap is cool then there isn't any pressure / heat.

On removing the rad cap i realised there wasn't any back pressure, no steam or heat from the rad filler neck, and coolant had only dropped slightly( 30ml to fill again )

There are no signs of any coolant leaks anywhere as far as a i can see, and i did pressure check on system and that was stable.

Any ideas on why radiator cap was cool and there isn't any pressure in radiator, could it be the radiator cap is loosing the pressure?

 

Any suggestions are appreciated.

 

 

 

[Judd]

Have you removed a heater hose and viewed the flow with the engine running, suggest both inlet and oulet pipes.

If good inlet and poor outlet could point to a heater matrix or valving issue, if there's little flow either in or out could the water pump impeller be spinning on its shaft?   probably a daft suggestion but you did ask 😉    oh and one other daft suggestion, and i ask this because of the convoluted route the auxilliary belt takes on my Prado...if the water pump is auxilliary belt driven it is turning in the right direction?

[Brom55]

Thanks for the reply Judd,

When i had the thermostat and coolant changed 4weeks ago, i also asked them to  back flush heater matrix, as i had used some head sealer in the original engine in 2021 and it clogged heater core. On picking up my car the cabin heater was much warmer so i though everything was good.

Within2 miles the temp went over half by 2/3 segments on the gauge and has been fluctuating ever since. Never any steam etc from the radiator or exp bottle and never any coolant loss

I had the matrix flushed twice more due to no cabin heat issue over the last 3 yrs anyway. I have removed the heater hose bleed valve and replaced it.

I find it hard to imagine the water pump failing between dropping it at the garage at 9.30 and picking it up at 3.30.

All the work which was done was a new thermostat and coolant refill, i thought the system needed burping which i have done approx 6 times and also had it filled using the vacuum method.

I am wondering if the radiator cap isn't holding pressure (but i not seeing any steam or coolant under the bonnet as far as i can see..??

 

The gauge just goes to half then 1 over, then 2 marks over but will then come  back down to half when cruising on low load.

I'm at a loss as only thermostat and coolant was changed originally 4 weeks ago.

[Judd]

One other thought.

Could the most recent coolant change have used incompatible coolants?   I understand OAT and the old standard glycol can form some sludge instead of mixing, its the devils own job trying to extract all previous coolant from an engine.

Wasn't thinking the water pump had failed completely but wondering if the impeller might be loose on its spindle so turning at a fraction of the rate it should, or worn?, loosening a heater pipe and seeing for yourself the type of flow rate there would iron that one out one way or the other, its also the method many of us used in times gone by when bleeding the cooling systems on our cars.

I don't know what the water pump impeller is made of, hopefully being Japanese good solid metal but i have heard of plastic impellers on some european cars where some of the impeller has worn away over time with obviously reduced efficiency also the plastic ones maybe more inclined to loosen on its shaft.

It sounds like the thermostat is doing its job, its typically when t'stat opens first time is when all of a sudden you can add a lot more coolant to the system, which is how it went this week after fitting a new water pump to my Prado, running for about 20 minutes on fast idle no movement when all of a sudden the tank is empty and could get a further 3 litres in.

Just out of interest the heater in my previous H6 Outback was virtually useless and never did improve over the years, the Forester heater a vastly better one.

 

[Brom55]

Thanks for the advice Judd.

When i took my Tribeca to my usual garage on 5 Nov i imagine they use their usual coolant although i didn't ask what it was as they have a good reputation so had no concerns of using crap coolant.

The curious thing is we drove 400 mls in Norfolk over a 5 day period, drove home to Derbyshire and had no issues at all.

2 weeks after the trip to Norfolk i had  my car booked in for the t'stat to be changed (an OEM i had sent for from US) and a change of coolant.

The car was fine when i dropped it off at 9.00am, when i picked it up at 3.30 the temp went to half which is the usual, but then continued to 3 marks over half way, which instantly worried me.

I rang the garage, they said bring it back tomorrow, (so they dropped the coolant again and replaced thermostat to rule out any problems, refilled coolant and said they had bled the system well with the front elevated as is recommended on forums ).

I picked it up again and no real change, temp still going 2 above half, so the garage is no wiser they admitted.?

*Over the last 4/5 weeks i have purchased the no spill funnel and burped the cooling system numerous times & some air did come out.

* pressure tested the cooling system and pressure held.

*Fitted a new rad cap and pressure tested before fitting it

* Then last week I had the non - OEM thermostat replaced with the one i bought from the US, and i bought Prestone coolant to ensure it was a good quality coolant and not a mix of different types, so it is Prestone in the system now.

* The mechanic vacuum filled the system to make sure there were no air pockets trapped, but temp still going high even today, and i have replaced the rad cap as above, and took the car for a 20ml drive, the temp is still going 2/3 marks above half, no steam or sweet smell etc.

When i got back home the expansion tank was half full, but no heat on the rad cap, so again i gently removed the rad cap..

I know that is a potentially dangerous thing to do, but again there wasn't any pressure whatsoever, no steam etc/ so i am really confused why after driving 20mls that there wasn't any pressure (danger of scald etc) after removing the rad cap, that is the strange thing i don't understand why so?

I am not sure how to confirm w/pump is working, but it was obviously fine during the trip to Norfolk and up to taking the car to the garage?

I am not experienced enough or have the garage room to start stripping the engine front to check the w/pump, although

i did consider dropping the coolant myself to see the impeller of the w/pump through the t'stat hole with t'stat removed, and re-fill the system very slowly myself.

The only thing i haven't  changed now is the coolant temp sensor, but i have one on it's way which should arrive next week.

I am wondering if the coolant temp sensor is showing a false reading as the engine doesn't steam, seem over hot when i check after a drive.

it is very odd, and i'm losing the will to live now. The car seems to drive ok, no loss of power etc.

 

[Judd]

22 hours ago, Brom55 said:

T

I am not sure how to confirm w/pump is working, but it was obviously fine during the trip to Norfolk and up to taking the car to the garage?

I am not experienced enough or have the garage room to start stripping the engine front to check the w/pump, although

i did consider dropping the coolant myself to see the impeller of the w/pump through the t'stat hole with t'stat removed, and re-fill the system very slowly myself.

The only thing i haven't  changed now is the coolant temp sensor, but i have one on it's way which should arrive next week.

I am wondering if the coolant temp sensor is showing a false reading as the engine doesn't steam, seem over hot when i check after a drive.

it is very odd, and i'm losing the will to live now. The car seems to drive ok, no loss of power etc.

 

Yes the temp sensor could well be an issue.

Regarding water pump flow rate, if you remove one of the heater pipes (obviously this weather the heater valve will be set to hot so allowing full flow) with the engine running the flow should be that of gentle garden hose, if you've removed and refitted the heater inlet pipe its then worth removing the return/outlet pipe , that should be flowing at the same rate and you'll have ruled out there being any trapped air in the heater radiator.

 

[Brom55]

Nice thought Judd ,I'll see what I can do, but it is a job I have to do outside so the weather will limit ability to check things but I think;

1- check flow into/out of heater matrix hoses as you suggest

2- replace coolant sensor at some point and check prior to fit, (and also confirm check on old one which will be interesting.)

* BTW, last night I replaced the radiator cap with a new one, (not OEM) but 0.9 pressure and drove approx 20mls, modest and fast accelerating.

The heater gauge was showing 2/3 marks over half,but not into the last red area, so according to the gauge the engine/coolant is overheating, am I right?

However,I checked the coolant temp within 2 min as soon as I got home with my OBD II reader, and it showed the coolant temp shown as 208° F/heit, ( 94° C ), which as far as I am aware, those are normal parameters?

I will attempt to do some more checks as above depending on weather etc 👌

[Siluro]

Not sure if this helps but my 2007 WRX allows the water to get to 97C before the fans kick in while idling. Temp drops to 86C and this repeats. Some numbers for you to compare. I monitored this with OBD reader as I just replaced my radiator. Good luck