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Discussion Starter #1
Hello all,
First post for me so be gentle!

Problem I have with my '96 155 2.0TS 16v is that when crawling in traffic the coolant boils over through the filler cap on the top of the expansion tank.

Recent history of the car:
Cam belt (& associated bits) needed replacing and boiling over problem evident, skint and was out of work so car used infrequently for a few months. When I got the dosh together to have cam belt changed (too big a job for me) my mechanic mate said that the filler cap was knackered as water poured through it when he had the header tank out. Replaced (with what looks like non-alfa original) filler cap and combustion gas tested (bottle of liquid on filler hole) whilst in for the belt. The test showed no bubbling and no discolouration of the liquid.
Problem continued, another mechanic mate gas tested again, still looks good, so assume head gasket is OK. Rad looked a bit iffy, so put a new one in a couple of weeks ago, old one had lots of fins missing. Temp gauge whilst motorway driving stays a little lower that before rad change. No overheating seen since, but then I'd not got stuck in traffic for a while. Today, encountered a traffic jam. Noticed after a while that temp gauge was rising quite rapidly, fan cutting in (as it always has) and spotted a trail of liquid in rear-view mirrors. Put on the heater which helped to drop it a bit and luckily got moving shortly after. At home refilled header (about a litre) and did some testing. Temp gauge sits happily on first white mark (about 70 c?) as it did when I first had it, fan kicks in for a few seconds about 4 or 5 times, everthing looking stable and then temp gauge starts to creep and coolant starts to boil out of the cap. I suspected that the cap "may" not be operating at the correct temp (as not an Alfa one) so topped up tank again (another litre roughly), fitted girlfriend's 146 (1600) filler cap and re-ran test. Same outcome.
My thoughts now are that:

1) Filler cap is not correct pressure (don't know whether the 146 one is the same as the 155).
2) Thermostat is not functioning properly (from reading some other posts)
3) Head gasket after all (as first mechanic said). Arrghh!!

Any guidance would be very welcome.

Sorry for the length of this, thought it best to give as much detail as possible.
Nick.
 
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I'd have to say get the cap replaced to be on the safe side but it's looking like either blocked radiator (airlock?) or the head gasket has gone.

wrinx
 

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Discussion Starter #3
Thanks for the reply Wrinx.
The thing I can't get me head (sorry for the poor pun) around is that the gas tests both were OK when it was hot, and the temps fine when driving. My normal trip to work is 5 mins normal roads, then 15 mins motorway and then another 5 mins street driving. Prior to changing the rad it occasionally boiled up if I'd queue after getting off the motorway but it's not done that since changing the rad.
I was thinking of doing an hour of so motorway driving today to see if the temp climbs, is that going to prove anything?

Nick.
 

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Discussion Starter #4
WRT Wrinx's post and thinking about a airlock I've just done some squeezing of the hoses to the rad. Coz I wasn't thinking I started by doing it with the filler cap still fitted. I can hear air being expelled from the filler tank (bubbling as I squeeze and hence displacing coolant) via the cap. Even a gentle squeeze caused air to come out of the cap.
Question is, from reading various posts on AO I was under the impression that the filler cap was supposed to keep coolant under some sort of pressure. Should it just let air out (IE no pressure retained in system)?

I've done the squeezing with the cap off as well to ensure no air lock, bleed plug on rad seeps when untightened....
 

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Nickg_pfc said:
Question is, from reading various posts on AO I was under the impression that the filler cap was supposed to keep coolant under some sort of pressure. Should it just let air out (IE no pressure retained in system)?
The cap should hold the system under pressure (yours clearly isn't), that may be the reason yours is boiling over (coolant under pressure boils at a higher temperature).
Also, are you using a propper engine coolant or have you just filled it with water?
Propper engine coolant boils at a much higher temperature than water, the stuff in my engine will not boil until it reaches about 180degC (not that it ever gets that high!).

What temperature is it actually getting to?
It should sit at close to 90degC the whole time, if it runs lower than that after it has warmed up the thermostat has probably failed in the open position.
 

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Discussion Starter #6
Thanks David,
I've been starting to come to the same conclusion regarding the cap. Sounds like the girlfriend's 146 needs one as well!! I have been wondering if I've got a strong enough mix. When I changed the rad I put in 2 litres of anti-freeze to 4 litres of water which topped it up. I guess the other 2.summat litres were in the heater and block. So I should have about a 30% mix. I didn't want to put loads of antifreeze in if it was just going to blow out the first time it got warm.

The temp gauge tends to sit at around 60-70 under normal driving conditions rising when poodling in traffic or wellying it, oil temp gauge only moves in wellying mode. So it sounds like the themostat is required as well. I don't think it's ever has sat near 90deg C in all the time I've had the car, since dec '96 (I got it 6 months old, ie 8 and half years).

If the thermostat is required I guess i'd do best to drain as much out and then when refilling put in the required anti-freeze first.
Does anyone know what the recommended water/anti-freeze mix should be?
Is there a recommended type of anti-freeze for standard road useage?
 

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Re anti-freeze mix, it is a lot easier to use a coolant that doesn't need diluting.

I'm using 4Life Advanced Engine Coolant (I think it is made by Castrol), cheapest place I've found it online is from the MG Owners Club who are actually located in the same building as Castrol Classic Oils (who can supply 4Life too).

4Life is a nice strawberry red colour :cool: and will turn yellow in the presence of combustion gasses, warning you of a headgasket failure.
Its boiling point is about 180degC and it is safe to -42degC.
 

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Discussion Starter #8
David C said:
Re anti-freeze mix, it is a lot easier to use a coolant that doesn't need diluting.

I'm using 4Life Advanced Engine Coolant (I think it is made by Castrol), cheapest place I've found it online is from the MG Owners Club who are actually located in the same building as Castrol Classic Oils (who can supply 4Life too).

4Life is a nice strawberry red colour :cool: and will turn yellow in the presence of combustion gasses, warning you of a headgasket failure.
Its boiling point is about 180degC and it is safe to -42degC.
Thanks David, I'm very tempted to go for that. I guess my plan of action should be :

Fit new cap (alfa) and check if problem still exists. If not then remove thermostat and test to see if operating correctly, replace as required. Drain full system. Refit stat and refill with 4Life.

One question, will 4life be OK seeing as I've had water/anti-freeze in there, IE will I have to measure what comes out to ensure I've got it all or will a little residual make no difference?
 

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It should mix fine, but to be 100% sure you could flush the engine with water and let it drain before filling with 4Life.
It is impossible to get all the coolant/water out of the engine block, so there will always be a little left behind.

Your 'fit new cap & check' plan looks spot on, also check to make sure the header tank its self isn't cracked (if it is it should be clear to see the stains where coolant has got out if it is cracked).
 

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Discussion Starter #10
David C said:
It should mix fine, but to be 100% sure you could flush the engine with water and let it drain before filling with 4Life.
It is impossible to get all the coolant/water out of the engine block, so there will always be a little left behind.

Your 'fit new cap & check' plan looks spot on, also check to make sure the header tank its self isn't cracked (if it is it should be clear to see the stains where coolant has got out if it is cracked).
I'll have a look. The squeezing of the rad hoses definitely caused air to be expelled through the cap, I loosened it and the hissing stopped.
 

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Discussion Starter #11
Hmmm.
I've fitted a new cap, same result from the hose squeeze test (air coming out of the top of the expansion tank). Looking closely at the tank itslef I'v enoticed there is a hole about 2-3 in diameter in the thread (facing the back of the car). It looks like either done in manufacture or has been drilled (not by me!). I've stuck some gaffer tape over the inside, refitted the cap and now no hissing. Checking the girlfriend's 146 and there is no hole in that. So the question now is, should it be there or has this been drilled (for some unknown reason) prior to my ownership??
Any other 155 (2.0l, 16V) owners have the same?
 
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