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  1. #11
    Join Date
    Jun 2001


    Quote Originally Posted by MarTer View Post

    New expansion tank & cap fitted.
    Water in expansion tank clean with absolutely no residue of any kind. No sign of any bubbles.
    Oil normal in sump & under rocker cover.
    Exhaust and engine power normal.

    Sounds to me like the Volvo engineer is short of work!!! Hang on first regarding the gasket and fix the cooling system.

    Look at what Vic wrote......firstly 30 PSI sounds wrong...maybe 10 and possibly 15 .

    Ask your self is te signs of oil in the fresh water cooling sytem or signs of oil on the bottom of the pressure cap..If not then I think you eed to look at how the caps and expansion bottle are fitted as it will not be the firast time I have seen an expansion bottle incorrecty fitted with the wrong radiator cap so preventing watr to draw back to the engine on cooling.

    Perhaps if you detailed exactly what was fitted as I suspect that the problem regarding pressure may be no more han normal activity caused by incorrect components . Can and does te water foow back to the engine when it cools from the expansion tank.???

    IF no traces of oil or sludge around the pressure cap then the gasket could b OK.
    Eastern Scotland and beyond.

  2. #12
    Join Date
    Sep 2008


    "the engine has only been run with the pressure gauge in place of the pressure cap"

    thats probably the source of the excess pressure- lucky you didn't blow off a water hose!

    good luck with the trials.

  3. #13
    Join Date
    Jan 2009


    Is that the correct cap pressure for the engine?
    Did you overfill the new system and the natural expansion pushed water out until it found it's correct level?
    Is the length of the cap correct for the expansion tank, if the cap is too short the valve in the cap won't be compressed enough to work correctly (had this problem in a car)?
    Is the system plumbed correctly?
    If the gasket failure is quite bad you will often see exhaust gas bubbles appearing in the water if you look in without the cap.

  4. #14
    Join Date
    Jul 2009
    south wales


    From what you are now saying it sounds like no more than overfilling the cooling system and it blowing out excess water when the engine gets warm. If that proves to be the case then your "engineer" owes you some money for making a meal of things - "heat guns", pressure tests, etc.

    There's a disease of sailors which aflicts me too, and it's called mechanical hypochondria. The symptoms are that you spot a problem and immediately assume that the cause is the most expensive and complicated one you can understand. I've done it many times.

  5. #15
    Join Date
    May 2001
    North from the Nab about 10 miles


    If you fitted a pressure gauge instead of a rad cap, you will get a build of pressure simply from coolant expansion. Had that on an old Daihatsu that had been fitted with the wrong rad cap which prevented it releasing steam. Spectacular when hoses started to blow off....

    Put the rad cap back on, and see if you lose coolant. If not, you have nothing to worry about.

    Rad Cap pressure gauges are only useful for checking for leaks. Pressurise the system to normal working pressure, then see whether it goes down quickly. If it does theres a leak somewhere - including a leaking gasket. The system will work at the pressure set by the rad cap unless it is faulty - usually letting pressure go too soon which may cause the coolant to start boiling off. Their limitation as a diagnostic tool is that it will not of course tell you where the leak is.
    Last edited by oldharry; 04-08-09 at 17:07.
    Is Conservation for wildlife or conservationists?

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