Compression/HG/Coolant issue?

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arctichotspur
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Compression/HG/Coolant issue?

Post by arctichotspur »

Hi guys.

I have a 1986 MR2 N/A with 140.000 km on it. Bought new in Norway and I think its same spec as UK.

The car runs good. Starts by just looking at it, idles beautifully, revs without problems. So what is the problem then?

1. After changing fuel filter and fuel breather valve I noticed the car is using coolant. I changed and bled the coolant system some weeks ago and I have found no leaks? I had not checked overflow tank since bleeding the coolant. I have now filled it up to full.

2. I have some white exhaust. It starts around 30 seconds after starting the car. I don't notice it while Im driving. It gets less after turning off the choke and the car idles around 800 rpm.Edit: I checked again and it looks like water is slowly coming to the exhaust pipe after starting. White smoke comes when there is sufficient water in end pipe. Tasted and smelled it and its water. Took the car for a "hard" ride and no white exhaust is coming out now...

3. I did a compression test and got high results on all cylinders.
#1: 195
#2: 198
#3: 192
#4: 200

These readings are all higher than manual states, but fairly even I think. Could it be carbon buildup?

I was first thinking that there was a leak in the head gasket, but the compression test made me unsure. Do you guys have any ideas. Or what would your next steps be? Or am I worrying too much :blush:

Thanks!


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Re: Compression/HG/Coolant issue?

Post by jimi »

I doubt it's the head gasket, your compression tests are fine, water from the exhaust on starting from cold is normal, just condensation, same with a little white smoke when cold.

You may not be using coolant at all, the tank is an expansion tank, the system will find it's own level.
To explain:-
Starting with the the tank topped up to the full mark and the cooling system full and bled.
When the engine gets up to temperature the liquid in the cooling system expands causing the system pressure to increase, this increase lifts the pressure cap on the cooling system allowing excess liquid to expand into the tank.
When you switch off the engine and it cools down liquid is drawn from the tank back into the cooling system. Now if your tank is full to start with, then when the pressure cap lifts and liquid flows into the the tank it may overfill the tank causing the excess to flow out of the overflow line on the tank cap, when it cools down and liquid is drawn back into the cooling system then the tank level will be lower than it was to start with.
Since any overflow happens when the system is up to temperature, normally when your driving then you are unlikely to notice it dripping under the car, leading you to suspect you are losing coolant but can't find a leak

On mine the normal level on the expansion tank is around 1/2 to 3/4 way between the two marks. If I fill it to the top mark it will (after a few cycles) end up at it's own level further down.
Or am I worrying too much :blush:


That may well be the case :laughing

HTH
Jimi
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Re: Compression/HG/Coolant issue?

Post by arctichotspur »

Thanks again Jimi for a thorough and well-explained answer :th:
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Re: Compression/HG/Coolant issue?

Post by jimi »

No problem :cool1: the trouble with the internet is because you don't know the technical background of people your never sure what level to pitch explanations at.
Don't want to insult people with an established technical background or overwhelm someone who is just learning :)
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Re: Compression/HG/Coolant issue?

Post by arctichotspur »

Hi again.

I noticed some drops under the car and I started looking further and discovered that I have a small coolant leak. It looks like small drops running down the water pump. Cambelt and water pump was changed last year(2000 km ago). Water pump is working as it should.

When I dry off the leak with paper small droplets come again only seconds later. This is with the car off. The area under the water pump is wet as coolant has dripped further down. The area above the water pump is dry.

Where would you guys start investigating and what would be your next steps?

Thanks.
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Re: Compression/HG/Coolant issue?

Post by jimi »

Unfortunately it sounds like the seals have gone on the water pump, It has a weep hole underneath, acts as a warning that the seals are on their way out
40046154.waterpumpweephole.jpg
Be very careful, if water is leaking out air will get in, which will cause problems with the cooling and 4A-GE's don't like overheating
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Re: Compression/HG/Coolant issue?

Post by arctichotspur »

Thanks Jimi. Tried some of the steps and was getting ready to remove waterpump. When I was going to remove the first 10mm bolt holding the pump I noticed that this was barely torqued at all. I could actually turn it by my fingers. This bolt was just above where I saw the droplets coming out.

I tightened the bolt and im going to fill up with water first to see if this was the source of my leak. It looked «dry» around the weep hole.

Fingers crossed!
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Re: Compression/HG/Coolant issue?

Post by jimi »

Hopefully that will sort it :th: keep an eye on your temp gauge for anything unusual, you may need to bleed the cooling if any air has got in, hopefully not :)
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Re: Compression/HG/Coolant issue?

Post by arctichotspur »

I dropped all the coolant before I started as I expected to remove and change the pump. So a full refill and bleed is on my list 😊
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