Head gasket or bust water pump?
 

Hi all,
I'm having an issue with my 95 850 t5, it suffered a burst pipe and lost all coolant so over heated. Since then, once hot, the coolant floods into and overflows out the expansion tank. I've replaced the tank as it had a small leak, new cap aswell. Local garage did the test for exhaust gas in coolant, none, but they still think headgasket is gone. I tried to take thermostat out, bolts rounded so local engineer took them out for me, he said the water pump must be faulty as the engine gets hot, but the radiator doesn't get that hot until run for quite a long time. Is it possible the water pump can pump at a reduced capacity? It is pumping as I took the hose of when running. No oil in coolant or coolant in oil. Drives fine, pulls fine, temp gauge goes to normal position. I've replaced the coolant temp sensor. Looking for advice before biting the bullet and pulling the head.
Any info greatly appreciated.
TIA

get a compression test done. that will rule in/out the head gasket, good psi is are 150psi upwards, but if its been 'sniff' tested then id say the head is good.

its rare the genuine water pumps fail but if its non genuine theres a chance the impeller has rusted, failed and fallen off. had one on a customers car a while back.

a good way to check for water pumps sucking ability is to rev it with the cap off the header tank and watch the water level drop as its drawn to the pump. this is a decent indicator of condition.

im inclined to say youve got another faulty or cracked hose, probably brought on by age, or youve got a collection of air pockets still in the system.

check the little one that feeds the turbo thats just infront of the brake servo booster, also the 2 small ones to the turbo, but a good inspection of them all wouldnt go a miss. let us know how you get on.

Thanks for that. I've checked the hoses all seem fine. Going to check compression as soon as I can. The coolant has been drained a few times now, if it's air pockets, how do I get rid of them?

Doogs

Stabbing in the dark a bit but have you tried diverting the coolant flow away from the heater matrix - pull the inlet outlet pipes at the firewall and connect with half inch ??? Hose and a couple of jubilee clips.

From personal experience some of your symptoms are indicative of a blocked matrix.

Gotta be worth investigating, will take you half hour tops once you have the hose and clips.

When my T5 expansion tank was overflowing numerous mechanics told me it was the head gasket but like you I was convinced it was not. Thankfully I was right and it was the combination of tank cap and blocked matrix. Only took Me about 60 hours to work it out !

Hy there,

Bigfella666,

I got approximately the whole post, but, "blocked matrix", what does it mean ?

VV 70

Diesel

Good to hear from you amigo, hope you have invested in 2 x spray bottles for the Megs at 4/1 and 8/1. How are you getting on ? Used Megs to clean 20 years of grime behind cooker and cabinets etc last weekend at 4/1 came off Like magic, which is why I rate it so highly.

The heater matrix takes the heat from the coolant and uses some if to give you interior warm air, located in the passenger footwell, if it is leaking there will be coolant in the footwell, if it is blocked it will prevent the low pressure circulation of coolant through the block etc and in my case caused the expansion tank to overflow.

Got so bad I ended up with VOL FCR constantly hooked up on live data in an attempt to ensure I was not cooking the engine !

If you google or look in the technical issues section here there are many articles on it - the matrix is a 70 quid fixand an hours work with 2 pairs of hands and as I understand it is responsible for many an 850 or V70 hitting an early grave.

All the best

Paul

Hy Paul,

Many thanks for these explanations. I not going to stay newbie forever... !

I will have a look.

Megyar was a galion ordered. As I said before, a test on the interior roof started to unstick it so I stopped immediately.
I will wait for spring to get it out an do a proper new installation (removal, clean, stick...)

Cheers.

Diesel

Diesel

For roof lining I would use Megs at no stronger than 10/1 ( same for alcantara ) and agree that for major cleaning of it you would be best to wait for the return of warmer weather. Much to my surprise it is also a fantastic stainless steel cleaner, in fact I have found it has almost endless uses so keep using !

Bigfe,

You're right. I finish to prepare my car for the winter and will start the roof in April may...

VV 70

Hi bigfella666
Thanks for the reply, no one has mentioned that so far. Only thing is, the heater is working great, if I turn it off though, it does make the problem worse. Would the heater work well if there is a blockage?