Head gasket job - why valves

[Dexter]

with compression test results like this (w124 e280 estate) why must I consider extra expense of valve work as part of head gasket job (typically an extra £240 on overal price)

160 160 150 125 150 160

After all car runs great and in the cold light of day is getting on a bit- can't underatand why head can't come off be skimmed and have new gasket set fitted for around £500

grateful for comment

 

[Glenn Smith]

No. 4 is a bit low, is the head gasket blowing, looks like itis on No. 4, so gasket would cure this, so you could do as you say, or maybe just a head gasket, skimming should only be done if needed.

 

[jberks]

The main cost is the labour to strip it down and reassemble. Plus the cost of the gasket set, bolts or whatever else is done as part of a gasket job. If there is any wear on the valves, then its advisable to do them at the same time. After all, how would you feel if you paid for the head gasket work, only to find you have valve problems 12 months later and the head had to come off again.

 

[Ian Brown]

If it was my car I would remove the valves check them, and get them ground back in if they look OK and for the sake of £30 get the head skimmed, I would never refit an alloy head without getting it skimmed

 

[television]

I do not understand why you want to do half a job, taking off the head is the hardest bit, take it to a specialist who will lap the vaves, replace any faulty guides,skim it and all you have to do is to slip it back on, and you know it is all perfect.

Malcolm

 

[Dexter]

Malcolm

I would agree with you if the valves were an incidental part of the job but Its the extra expense involved (£240 on my quotes). I realise that the garages need to cover themselves in case of what they might find when they take the head off but in my case with no real concerns after the compression test it should be made more painless. I guess it is a case of them needing to guarantee the work although I have not succeded in getting any firm commitment from any garage with regard to expected longestivity going forward in terms of years or mileage, even for the full job!

If I was a mechanic and a bloke in an old car drove up I would make sure I knew what his threshhold was ie ratio of expense to expected longetivity - was he looking to run it for the next 100k or in my case just get a 2/3 years of relatively maintenance free enjoyable motoring - job done!

There are'nt many people mad enought to want to spend £12-1400 on a 12 year old car and the market ie. what people are people are prepared to pay should dictate how the garages pitch for the business. I get the impression that no one really wants the job perhaps a case that I have reached the design life of the vehicle or perhaps simply that you cant run a post 1990 car for 20 years anymore.

 

[Glenn Smith]

Question is where do you stop, personaly I would check the valves for wear, clean them up and lap in very carefully, a hard grinding paste session could take many thousands of miles of the life of the valve and cause other problems with valve sealing. It's a difficult choice if you're not doing the job yourself, still wouldn't skim head if not needed, have done loads, no probs.

 

[television]

OK you do have a point, there is a difference in running a car because you love that car, or when do you say enough is enough on a 20 year old car.
the worst thing here is that it takes say 6 hours to dismantle and 5 hours max to put back, plus two hours working on the head. the charges made by garages,seem to put it out of all context. Not so long ago we could all afford to have these jobs done, OK I always did my own and enjoyed doing it.

I wonder if your gagage that did the compression test, checked if it was valves or rings on number 4.

Malcolm

 

[kth286]

Dexter

I tend to agree with you.

So, what is the history leading up to you getting the compression readings done in the first place ??????? Why did you get it done ?????????

As television says, it may not be the head anyway !!!!!!!!

Let us all know a bit more - the quality of the input dictates the quality of the output on this type of forum.

Regards

 

[Dexter]

David

After discovering oil patches on drive I got took it to a number of garages read a lot of forums and the consensus seemed to be that it was more likely than not the HG seeping.

With no symptoms in oil or coolant I was sceptical and closer insopection by my local MB dealer revealed leaks from lower timing case, sump gasket and evidence of seapage around rear of head gasket (back offside).

no significant ammount of oil being lost or contamination and advise seemed to be that all work could be simultaneos to the HG job - fair enough as the jobs are easier when done with engine out.

My local independant seemed surprised that I was considering the job partly because of age of car and partly as she is running fine. Question is should I be proactive and keep her scrupulously maintained or suffer the annoyance of the oil patches and see if I can get achieve my objective of 2/3 years motoring without the big bill. The oil spots I can live with but the dark cloud of the HG job seems to hang over me making me agonise over every other purchase decision.

Consensus on forums seems to be split but ultimately the decision will be made on economic grounds. I am torn between the 'If it ain't broke...' and my natural desire to stay ahead of any future problems. The happy medium is an acceptable quote for the HG job which for me would not involve all this fuss over the valves given that my compression test was quite positive.

Anyone know of a former MB technician in Devon/ Somerset/ Bristol region who could do this job over a weekend or two and not make a meal of it?
Then we can all be happy

Grateful

 

[mlc]

I think your choices are quite easy really. If the oil leaks are not too bad, the performance is not effected and you dont want to spend money until you have to, then dont fix it. If you need the car for work, cant manage without it and the drive mustn't be stained, then get it do quickly.

If you continue to monitor the situation carefully then you could wait until it gets worse and then do the repair. Alternatively you make consider that if you could get say antoher 12 months out of the car you could trade it for a newer / beter model.

Only you can make this desicion, but it does seem to me that you dont want to spend the money, so since its not safetly critical dont.

Mark.

 

[kth286]

Dexter

OK, so you can put a drip catcher under the car to avoid soiling your drive - available from Halfords.

BUT you seem to have an engine problem because the compression is too low on that one cylinder, and that needs clarifying/sorting.

The min compression should be 12 bars approx. and your highest is 11.04 bars but they are fairly consistent so no real worries, except the low one.

The MAXIMUM difference between cylinders should be 1.5 bars, but yours is 2.415 bars, so there IS a problem.

You need to determine whether it is valves (in the head) or rings (in the block).

One way is to pour a small amount of oil (teaspoon) in the spark plug to seal the rings of the offending cylinder and check compression again.

If it is now much better, then problem is rings - if no better - then problem is likely valves.

If it was the cylinder gasket there would normally be low compression on two adjacent cylinders, which is not your case.

The low compression on one cylinder apart from likely being valves, could be a worn camshaft lobe on that cylinder and you would expect to experience slight lumpy idling also.

You would need to remove the cam cover and look at both cam lobes for that cylinder (remember your car has two overhead cams - one for exhaust valves and one for inlet valves)

Hope this helps.

Regards

 

[vigitalmode]

Anyone know of a former MB technician in Devon/ Somerset/ Bristol region who could do this job over a weekend or two and not make a meal of it?
Then we can all be happy

Grateful

Dexter, I am not a former MB tech but I am a qualified technician with 8+ years of experience with all makes of cars. I have however always had mercedes and have considerable experience with them. I now have my own business specialising in engine rebuilds and repairs. I am meticulous with my work and get the job right first time. I would be happy to look at or do the work on your car and I don't charge the earth either. I could pick up your car or maybe lend you one if needed. Could do it over a weekend, no problem. I am based near Newton Abbot (south Devon) and my business line is 01626 836323. Mobile 07792 991175. Cheers Alex