Car keeps over heating and using coolent PLEASE HELP

[oBladeo]

Took my car to Toyota the other day and they said it was the pipes above the petrol tank leaking and the radiator so i said ok fix it £700 later and it's still broke.

What happens is when i drive for a while and the temp gauge on the dash gets to 1/2 way then i drive 70mph then that’s when the temp starts to go up but as i go up and down hills and round sharp corners the temp drops quick. I think there is a air lock so i parked it's on a hill yesterday and started to bleed all the air out then parked it's at home. Then this morning before i set off for work i just made sure everything was toped up and fine. I got to work and it needed toping up loads the problem is i can't see any water dripping and there’s no water in the oil. The only thing i have noticed is the over flow pipe on the catch tank keeps letting water out at revs of 5K+. Please help me i need to get this fixed before i start my new job on the 10th

[PW@Woodsport]

dont wish to put a downer on it but sounds very head gaskety...sounds as if the system is pressurizing and the pressure cap is opening at 0.9bar taking coolant with it.A blown head gasket on an mr2 hardly ever produces water in the oil or vice versa,its nearly always a break in the gasket between the water jacket and a cylinder,and usually number 4 as well.They tend not to let go all at once either so you get this gradual pressurizing and loss of coolant over time,the pressurizing will find the weakest point on the cooling system and blow it,hence the need for new heater pipes above the fuel tank and a new rad.Now that they are fixed the pressure has nowhere to go except out of the pressure cap.

This may not be 100% a HG failure though,a knackered water pump will produce very similar HG symptoms as will a blocked or stuck thermostat.

My advice is to leave the car running with the pressure cap off and topped right up to the brim,watch the water to see what it does....is there a fine stream of constant bubbles or a fine mist of bubbles? do they become more frequent with engine revs?If you have a friendly garage nearby ask him if he will do a sniff test.This involves him holding the probe of his 4 gas analyser over the top of your coolant filler point so that its sniffing the steam coming off it.If the Hydrocarbon reading (HC) goes up at all to what it was reading before the test then the gasket has 100% gone as the only place hydrocarbons (unburnt fuel) can enter the cooling system is via the head gasket (or a crack in the block but unlikely).

If it passes the sniff test id change the thermostat straight away followed by an inspection of the water pump if that doesnt work.Hope some of my waffle helps,let us know how you get on.

[David_Aston]

Hmm I had a similar problem and I let it go for a few weeks (just got the car) then the Cylinder cracked (so new head gasket) and new engine head. Just had the main pipe fixed on mine at my local garage cost me £150 now I have no problems (apart from the heater no longer works).

To me it sounds head gaskety

[oBladeo]

I hope not that’s all i need.

The engine can just sit there for ages just ticking over with out any bubbles. It’s just when I rev it :-S

Could it be a air lock somewhere in the system and that I’ve just not bled it up right?

So if the engine is using all the water where is it going?

[oBladeo]

I hope not that’s all i need.

The engine can just sit there for ages just ticking over with out any bubbles. It’s just when I rev it :-S

Could it be a air lock somewhere in the system and that I’ve just not bled it up right?

So if the engine is using all the water where is it going?

[Paul R]

I hope not that’s all i need.

The engine can just sit there for ages just ticking over with out any bubbles. It’s just when I rev it :-S

Could it be a air lock somewhere in the system and that I’ve just not bled it up right?

So if the engine is using all the water where is it going?

Do you get any excessive steam out of the exhaust?

Do a compression test/get someone to do one for you.

I've got a compression guage - how far away are you? I'll show you how to do a compression test if you like?

Paul.

[oBladeo]

Thanks for the help i'm going to take in to toyota i need it fixing can't be late for my first day. Thanks for the help anyway

HOPE YOU ALL HAVE A GOOD NEW YEAR

[PW@Woodsport]

hi paul,compression tests are only conclusive when you have a more advanced HG failure...a finely blowing HG caught in the early stages wont show a noticeable enough drop in compression to say conclusively if the gasket has gone or not (you can get a 5% difference in compression across the cylinders on a perfect engine).

A compression test may indicate the problem if the blow is big enough but in my experience the engine tends to run very badly and misfire at this stage anyway.

A sniff test is 100% conclusive no matter how fine the break in the gasket is whereas a compression test may not pick it up.

[Paul R]

hi paul,compression tests are only conclusive when you have a more advanced HG failure...a finely blowing HG caught in the early stages wont show a noticeable enough drop in compression to say conclusively if the gasket has gone or not (you can get a 5% difference in compression across the cylinders on a perfect engine).

A compression test may indicate the problem if the blow is big enough but in my experience the engine tends to run very badly and misfire at this stage anyway.

A sniff test is 100% conclusive no matter how fine the break in the gasket is whereas a compression test may not pick it up.

Yes but it *could* pick it up. I always like to do the cheap and easy tests first. No harm in doing it and it could show up the problem straight away!

Paul.

[PW@Woodsport]

i'm going to take in to toyota

Thats the last thing id do...wouldnt let those muppets service a pram,i hope you dont suffer with them like others have,good luck and happy new year.

[PW@Woodsport]

paul not wishing to be argumentative but how are you going to know the difference between a cylinder that just has a slightly lower CR due to engine wear and one that has a slightly lower CR due to a weeping HG?

All im saying is a compression test isnt conclusive,a sniff test is.

[Paul R]

Well it's worked for me before - I will say no more!

Like I said, no harm in doing a compression test.

How do you do a sniff test?

Cheers,

Paul.

[PW@Woodsport]

i absolutely agree,no harm at all in doing a Comp test,its just the results that can be a little misleading sometimes,i wouldnt like to rely on a 5% drop in compression (for example) being an indicator of the gasket gone,pull the head off,replace the gasket and rebuild only to find the 5% drop in comp is still there and so is the problem,but yes if the gasket has reached a blown enough state a comp test should show it up as maybe a 20% drop in compression,which i would say is proof enough,however where do you draw the line between a slightly lower compression due to engine wear?

The sniff test will pick up a HG failure even when the blow is that small that the compressions will all appear the same.

It relys on the fact that a four gas analyser(the one used for MOT emission checks) will pick up hydrocarbons in air as low as 1 or 2 PPM (parts per million).Note how many ppm of HC (which is basically unburnt fuel/exhaust gas) the analyser is reading in air then hold the probe over the coolant point so its "sniffing" a sample of coolant vapour.If the HC ppm reading goes up by even 1 or 2 ppm then its picking up exhaust gas in the coolant,the only place that can enter the coolant is via the HG.From experience the sniff test shows an increase in HC by 500-1000ppm with a finely blown HG.Its a totally conclusive way to check but you need a friendly local garage who is prepared to carry out this check.

[oBladeo]

Thanks for the help it was the head gasket after all thanks for the help

[gtech]

Hiya Paul (woods), happy new year to you and your lass....Very informative article that on the HG and Hydrocarbons, I get the impression that if you have a friendly garage then this is the cheapest and easiest option to go for.....All sounds very similar to some problems I have at the moment, only noticed yesterday when I was bleeding the cooling system to try and get some decent heat out of the heater.

When I hold the revs at about 2k, rad cap off, there is a continuous stream of very fine bubbles (as if midgets are fartting in there ) with the result tha the top layer of warter in the neck becomes very frothy, increase the revs and it disappers to a degree and then you get BIG bubbles...glup glup.

Finally got some heat out of the heater, but if it follows a pattern, the coolant will be down in a few days and the heater blowing cold again.....DEFINATELY no water leask, throughly checked.

Maybe worth a sniff test me thinks.

Graeme

[Paul R]

Hi,

How did you find out??

Cheers,

Paul.

[PW@Woodsport]

hi g mate,happy new year to you and yours as well! by the sounds of things you have a HG on its way too,although a dodgy water pump can also show similar signs its really the combination of fine water bubbles and a loss of coolant that make it more of a HG problem.

As we have discussed in this thread a compression test might show it up but a sniff test will 100% confirm either way.Theres also a chemical test kit but i have never used them so i cant comment on their effectiveness.

As mentioned before the problem with the comp test is that it wont differentiate between a weep in the gasket and a slightly lower cylinder compression due to worn rings or valves.If the blow is big enough though the comp test will show the problem.

Hope you get it sorted soon mate,catch up with you soon and i will be attending a few NE meets when i get the old girl up and running.