Thread: Disco ran hot and lost power

Has it lost compression?

Hate to be bearer of bad news it sounds like at best a blown head gasket or worst cracked head.Happened to mine could not tow camper above 90 klms ended up complete rebuild thats when head was found to be cracked.No of two others who have discos and after getting hot one had blown gasket the other a cracked head.

Firstly, it would be worth considering a low level coolant alarm. You can get them for around $100 with a red light and audio alarm. They are so critical because if you loose coolant - the temp sensor will read air temp and indicate almost normal temperture, but by then it's too late.

But you say that your not loosing coolant. So a couple more possibilities... the timebelt may have stretched and put the timing out, or perhaps the tappets need looking at. Maybe your water pump is tired or the rad stuffed.

I had a similar problem once and I found that the heat effected the internal strength of the elbow turbo pipe (closest to the firewall) and the inner part was collapsing under load and then under normal idel the problem would disapear and you could not tell the hose was crook, making it really hard to diagnose. When the hose was removed you could see all the inside stuffed and blocking the airflow !

this may not be your problem but might be worth a check !

CHeers

Originally Posted by Dougal

Has it lost compression?

I think that is next on the cards to check as I have ran out of ideas, I checked valve clearance today and they weren't bad, just a tickle on a few. Funny thing though as I usually like to do them hot I waited 1/2 hr to cool and rechecked and found they had nipped up a bit, (just for curiosity)I suppose the change is within the allowable design variance, just like when clearances were given as a range eg. 2-4 thou.

Checked inside the inlet pipe elbow before turbo and looked good. What really annoys me is that I had been contemplating purchasing the coolant alarm as advertised on this site but the funds didn't allow it at the time and I was going to wait a fortnight until I got some holiday pay...2 weeks too late! Head gasket I can deal with, but cracked head, then I am really in the brown stuff! Any other symptoms of a head gasket gone that I am missing???

If the head gasket is leaking, you might see some bubbles in the expansion tank when you rev it. Also the top radiator hose goes very hard due to the pressure build up in the cooling system. It may only be a slight leak at the moment with a slight loss of coolant under load. It may stay like that for months before it really lets go (thats assuming it is the headgasket). Radiator places can also do a gas test (check for exhaust gas in cooling system) but they will want to sell you a new radiator etc, etc.

If it is the head gasket - dont panic. I just helped my brother in law remove his 300Tdi head in just over 2 hours (another story!). A pressure test and light skim will cost around $200 plus another $150 for gaskets and head bolts etc. All up no more than $400 if you do it yourself.

Tried to get it booked in for a compression check but can't get it looked at for 2 weeks, the mechanic asked why do I want the compression checked when it isn't using water or there are no bubbles in the coolant though, he reckons it's more a fuel issue (because of the high EGT's)but nothing has changed on the fuel side of things and kept saying it's a boost issue but boost is OK it 's running 15 psi. max.

G'day Pawl, Just re read your posts, I would remove the turbo unit and check the compressor wheels. Any EGT's over 750 deg will potentially damage your exhaust side compressor wheel, and you may also find the inlet impeller has been touching the housing if the exhaust wheel has been damaged/ distorted causing imbalance. Is it any noisier under boost than before? This can also be a contributor to your fuel consumption possibly. Also, it is concievable that the overheat may have caused some piston damage, even nipping in the bore. A compression test will show this up. 450Psi is the min I would expect from these engines, hot and cranking at a good rate, un oiled(, NEVER oil a diesel engine to compression test unless you know what you are doing)
However,Usually, heating this much WILL cause a distortion of the head and a blown gasket, dosen't have to be into the cooling system, could be between cyliders, this will kill the performance. Not seen it yet with a Tdi, so far all have gone into the cooling system or a pushrod tube, causing massive crankcase pressure....or externally out the back of number 4...after an overheat.
Hope you find the prob!
JC